NEET Chemistry Formula Handbook for All Chapters

Students must regularly learn and revise the important formulas in all chapters of NEET Chemistry Formula Handbook for all Chapters. The attached handbook has all chapters which will come in the NEET exam for NEET Chemistry Formula Handbook for all Chapters. It has full details of all formulas which are applicable in all chapters. The handbook has been designed by NEET teachers and all formulas have been given chapter wise. Please see the list of chapters below for which you can download the pdf of formulas.

This NEET Chemistry formula handbook gives a quick revision of the important formulas and laws from all chapters of physical, inorganic and organic chemistry. It starts with Some Basic Concepts of Chemistry, Structure of Atom, States of Matter, Thermodynamics, Equilibrium, Solid State, Solutions, Electrochemistry, Chemical Kinetics and Nuclear Chemistry, and then moves on to the inorganic and organic chapters including Alcohols, Phenols and Ethers, Aldehydes, Ketones and Carboxylic Acids, Amines, Haloalkanes, Hydrocarbons and Polymers.

Contents

1. Some Basic Concepts of Chemistry
2. Structure of Atom
3. State of Matter
4. Thermodynamics
5. Equilibrium
6. Solid State
7. Solutions
8. Electrochemistry
9. Chemical Kinetics and Nuclear Chemistry
10. Surface Chemistry
11. Hydrogen
12. S-Block Elements
13. P-Block Elements
14. Coordination Compound
15. Organic Chemistry
16. Alcohols, Phenols and Ethers
17. Aldehydes, Ketones and Carboxylic Acids
18. Amines
19. Haloalkanes and Haloarenes
20. Hydrocarbons
21. Polymers

1. SOME BASIC CONCEPTS OF CHEMISTRY

(1). Number of molecules in W(g) of substance = \(\frac{W(g) \times N_A}{GMM}\)
(2). Molality (m) = \(\frac{\text{No. of moles of solute}}{\text{Mass of solvent in kg}}\)
(3). Number of molecules in V litre of gas at S.T.P. = \(\frac{V N_A}{22.4}\)
(4). Number of gram atoms = \(\frac{W(g)}{GAM}\) (GAM → gram atomic mass)
(5). Number of gram molecules = \(\frac{W(g)}{\text{Gram molecular mass}}\)
(6). Dilution formula: M₁V₁ = M₂V₂
For mixing two solutions of the same substance: M₁V₁ + M₂V₂ = M₃(V₁ + V₂)
Molarity can be directly calculated from % by mass (w/w) if density is known: Molarity = \(\frac{\% \times 10 \times d}{GMM}\)
(7). Mass of 1 atom of element = \(\frac{GAM}{N_A}\)
(8). Mass of 1 molecule of substance = \(\frac{MM}{N_A}\) (MM → Molar mass)
(9). T(K) = T(°C) + 273.15
(10). Relative atomic mass = \(\frac{\text{Mass of an atom of the element}}{\frac{1}{12} \times \text{Mass of an atom of carbon (C-12)}}\)
(11). Number of molecules in n moles of substance = n × N_A
(12). Mass % of an element in a compound = \(\frac{\text{Mass of that element in 1 mole of the compound}}{\text{Molar mass of the compound}}\) × 100
(13). Mass percent = \(\frac{\text{Mass of solute}}{\text{Mass of solution}}\) × 100
(14). \(\frac{X_B}{1 - X_B} = \frac{\text{molality} \times M_A}{1000}\) where M_A - mass of solvent
(15). Molarity (M) = \(\frac{\text{No. of moles of solute}}{\text{Volume of solution in litres}}\) mole/L
(16). Avogadro's No. N_A = 6.022 × 10²³
(17). T(°F) = \(\frac{9}{5}\) T(°C) + 32
(18). Molecular mass = 2 × vapour density
(19). Mole fraction of A = \(\frac{\text{No. of moles of A}}{\text{No. of moles of solution}}\)

2. STRUCTURE OF ATOM

(1). Wavelength of matter wave
λ = \(\frac{h}{mv}\)
λ = \(\frac{h}{p}\)
λ = \(\frac{h}{\sqrt{2Em}}\)
Where, E = Kinetic energy
(2). Total number of nodes = n - 1
Radial nodes = n - l - 1
Angular nodes = l
(3). Number of neutrons = A - Z
(4). Number of subshells in n^th shell = n
Number of orbitals in n^th shell = n²
Number of electrons in n^th shell = 2n²
Number of orbitals in subshell = 2l + 1
Number of electrons in subshell = 2 (2l + 1)
(5). Energy of quantum of radiation according to Planck's quantum theory: E = hν
(6). hν = hν₀ + \(\frac{1}{2}\) m_ev² (Einstein's photoelectric equation)
(7). Line spectrum of hydrogen
\(\bar{\nu} = 109677 \left( \frac{1}{n_1^2} - \frac{1}{n_2^2} \right)\) cm^-1 where \(\bar{\nu}\) is wave number and \(\bar{\nu} = \frac{1}{\lambda}\).
Where n₁ = 1, 2, .....
n₂ = n₁ + 1, n₁ + 2, .....
(8). Bohr's model of hydrogen atom
(a) Frequency of radiation absorbed or emitted during transition: ν = \(\frac{\Delta E}{h}\) = \(\frac{E_2 - E_1}{h}\)
E₁ = Energy of lower energy state
E₂ = Energy of higher energy state.
(b) Orbit angular momentum of an electron: m_evr = n · \(\frac{h}{2\pi}\), where n = 1, 2, 3, .....
(c) Energy of stationary states: E_n = -2.18 × 10^-18 \(\left( \frac{Z^2}{n^2} \right)\) J
(d) Radii of the stationary states/orbits: r_n = 52.9 × \(\left( \frac{n^2}{Z} \right)\) pm
(9). Energy gap between the two orbits: ΔE = R_H \(\left( \frac{1}{n_i^2} - \frac{1}{n_f^2} \right)\)
Where R_H = 2.18 × 10^-18
Where, n_i = initial orbit
n_f = final orbit
(10). Atomic number (Z) = Number of protons in the nucleus of an atom = Number of electrons in a neutral atom
(11). Heisenberg's uncertainty principle: Δx × Δp ≥ \(\frac{h}{4\pi}\) ; Δx × mΔv ≥ \(\frac{h}{4\pi}\)
(12). Speed of light is equal to the product of frequency and wavelength of light: c = νλ
(13). Mass Number (A) = Number of protons + Number of neutrons

3. STATE OF MATTER

(1). Van der Waals Equation: \(\left( P + \frac{an^2}{V^2} \right)(V - nb) = nRT\)
(2). Combined Gas Equation: \(\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}\) ; (n, R constant)
(3). Dalton's Law of partial pressures: P_Total = P₁ + P₂ + P₃ + ....
(4). Ideal gas equation: PV = nRT
M = \(\frac{dRT}{P}\)
(5). Charles's Law: \(\frac{V_1}{T_1} = \frac{V_2}{T_2}\) (at constant P and n)
(6). Avogadro's Law: V = kn (at constant P and T)
(7). Partial Pressure in Terms of Mole Fraction: P_i = x_i P_total
(8). Boyle's Law: P₁V₁ = P₂V₂ (at constant T and n)
(9). Compressibility factor Z = \(\frac{PV}{RT}\) (for 1 mole of Gas)

4. THERMODYNAMICS

First law of thermodynamics
ΔU = q + W
Enthalpy of reaction
ΔH = ΣΔ_fH° (products) - ΣΔ_fH° (reactants)
By convention heat of formation of every element in its standard state is arbitrarily assumed to be zero.
Δ_subH° = Δ_fusH° + Δ_vapH°
Heat Capacity
C = \(\frac{q}{\Delta T}\)
Specific heat capacity c_s = \(\frac{q}{m\Delta T}\)
Molar heat capacity c_m = \(\frac{q}{n\Delta T}\)
Energy changes
ΔU = q_v, ΔH = q_p
q_v → heat exchange at constant volume
q_p → heat exchange at constant pressure
Enthalpy
H = U + pV
Relation between ΔH and ΔU
ΔH = ΔU + pΔV Or
ΔH = ΔU + Δn_gRT
C_p - C_v = R
ΔS = \(\frac{q_{rev}}{T}\)
ΔG = ΔH - TΔS
ΔG° = -RT ln K

5. EQUILIBRIUM

(1). K_w = K_a × K_b
(2). K_i = \(\frac{[A^+][B^-]}{[AB]}\)
(3). K_sp = [A^y+]^x [B^-x]^y
(4). ΔG° = -2.303 RT log K
(5). K_a = \(\frac{[A^-][H_3O^+]}{[HA]}\)
K_b = \(\frac{[B^-][OH^-]}{[BOH]}\)
(6). K_w = [H⁺][OH^-] = 10^-14 at 25°C
(7). pH = -log [H⁺]
(8). pK_w = pH + pOH = 14 at 25°C
(9). K_p = K_c(RT)^Δn
(10). Hydrolysis of salts
(i) For a salt of strong acid and weak base: pH = \(\frac{1}{2}\)[pK_w - pK_b - log c]
(ii) For a salt of weak acid and strong base: pH = \(\frac{1}{2}\)[pK_w + pK_a + log c]
(iii) For salts of weak acid and weak base: pH = \(\frac{1}{2}\)[pK_w + pK_a - pK_b]
(11). Equilibrium constant, K_eq = \(\frac{K_a}{K_b}\)
(12). K_a or K_b = cα²
(13). Concentration quotient, Q = \(\frac{[C]^c[D]^d}{[A]^a[B]^b}\)

6. SOLID STATE

(1). Density of Cubic Crystal System
ρ (or d) = \(\frac{Z \times M}{a^3 \times N_A}\) g.cm^-3
Where, Z = number of atoms per unit cell
N_A = Avogadro's Number
M = Gram atomic weight of element (g. mol^-1)
a = edge - length
(2). Radius-ratio in ionic solids

(3). Radius of atom, number of atoms per unit cell and packing fraction

(4). Packing Fraction (p.f.) = \(\frac{\text{Volume occupied by particles (per unit cell)}}{\text{Volume of unit cell}}\)
Contribution of each atom present on the corner = \(\frac{1}{8}\)
Contribution of each atom present on the centre of face = \(\frac{1}{2}\)
Contribution of each atom present on the body centre = 1
Contribution of each atom present on the edge centre = \(\frac{1}{4}\)
(5). Seven crystal system with dimensions:
(a) Cubic: α = β = γ = 90°, a = b = c
(b) Tetragonal: α = β = γ = 90°, a = b ≠ c
(c) Orthorhombic: α = β = γ = 90°; a ≠ b ≠ c
(d) Monoclinic: α = γ = 90°; β ≠ 90°; a ≠ b ≠ c
(e) Hexagonal: α = β = 90°; γ = 90°; a = b ≠ c
(f) Rhombohedral or trigonal: α = β = γ ≠ 90°; a = b = c
(g) Triclinic: α ≠ β ≠ γ ≠ 90°; a ≠ b ≠ c

7. SOLUTIONS

(1). Depression in freezing point
ΔT_f = K_f × m
K_f = \(\frac{RT_0^2}{1000\, l_{fusion}}\) = \(\frac{M_A R T_0^2}{1000\, \Delta H_{fusion}}\)
(2). Dissociation of solute
(A)_n → nA
i = \(\frac{1 + (n - 1)\alpha}{1}\) {α = degree of dissociation}
(3). P_sol = P_A° X_A + P_B° X_B = (P_B° - P_A°)X_B + P_A° (Raoult's law)
(4). Osmotic pressure
π = CRT
For isotonic solution, π₁ = π₂
(5). \(\frac{1}{P_{sol}} = \frac{Y_A}{P_A^o} + \frac{Y_B}{P_B^o}\)
(6). Relative lowering of vapour pressure
\(\frac{P_A^o - P}{P_A^o}\) = χ_B {χ_B = mole fraction of solute}
(7). Y_A = \(\frac{P_A}{P_T}\); Y_B = \(\frac{P_B}{P_T}\)
Where Y_A and Y_B are mole fractions in vapour phase and P_A = P_A° X_A : P_B = P_B° X_B
(8). Elevation of boiling point
ΔT_b = K_b × m
K_b = \(\frac{RT_0^2}{1000\, l_{vapour}}\) = \(\frac{M_A R T_0^2}{1000\, \Delta H_{vapour}}\)
Where, m = molality
M_A = molecular mass of solvent
(9). Molality (m) = \(\frac{\text{Number of moles of solute}}{\text{Weight of solvent (kg)}}\) mole/kg
Molarity (M) = \(\frac{\text{Number of moles of solute}}{\text{Volume of solution (L)}}\) mole/L
Normality (N) = \(\frac{\text{Number of gram equivalent of solute}}{\text{Volume of solution (L)}}\) g equiv/L
Formality (F) = \(\frac{\text{Number of gram formula mass}}{\text{Volume of solution (L)}}\)
(10). Van't Hoff factor
i = \(\frac{\text{Experimental colligative property (observed)}}{\text{Calculated (normal) colligative property}}\)
\(\frac{P_A^o - P}{P_A^o} = \frac{i \times n_B}{(i \times n_B) + n_A}\)
ΔT_b = i × K_b × m
ΔT_f = i × K_f × m
π = iCRT
(11). Association of Solute
nA → (A)_n
i = \(\frac{(1 - \alpha) + \frac{\alpha}{n}}{1}\) {α = degree of association}
(12). Henry's Law
p = K_H.X
p = partial pressure of gas in vapour phase
K_H = Henry's law constant
X = Mole fraction of gas

8. ELECTROCHEMISTRY

(1). Ohm's law ⇒ V = RI
R = ρ \(\frac{l}{a}\)
V = Potential difference
R = Resistance
I = Current
ρ = Specific resistance (resistivity)
l = length of conductor
a = cross-section area of conductor
(2). Conductance G = \(\frac{1}{R}\)
Specific conductance (conductivity) κ = \(\frac{1}{\rho}\)
(3). Cell constant σ = \(\frac{l}{a}\)
κ = G.σ
(4). Molar conductance Λ_M (or Λ_C) = \(\frac{1000 \times \kappa}{C\ (\text{or } M)}\) {C = concentration of electrolyte in terms of molarity}
(5). Equivalent conductance Λ_N (or Λ_C) = \(\frac{1000 \times \kappa}{C\ (\text{or } N)}\) {C = concentration (normality)}
Λ_M = Λ_N × (n - factor)
Λ₀ = lim_C→0 Λ_C {Λ₀ = equivalent conductance at infinite dilution (or zero concentration)}
(6). For weak electrolyte, Λ_C ∝ \(\frac{1}{\sqrt{C}}\)
For strong electrolyte, Λ_C = Λ₀ - B(C)^1/2 {B = constant}
(7). At infinite dilution, for an electrolyte A_xB_y
A_xB_y ⇌ xA^y+ + yB^x-
Λ°_AxBy = xλ°_A + yλ°_B {λ°_A, λ°_B = equivalent conductance at infinite dilution of cation and anion}
= xλ°₊ + yλ°_-
λ°_C = kμ°_C {μ = ionic mobility, K = 96500 coulomb}
μ = \(\frac{\text{Ionic velocity}}{\text{Potential gradient}}\)
(8). For a weak electrolyte, (CH₃COOH ⇌ CH₃COO^- + H⁺)
Degree of dissociation, α = \(\frac{\Lambda_M}{\Lambda_0}\), K_eq = \(\frac{C(\Lambda_M / \Lambda_0)^2}{1 - (\Lambda_M / \Lambda_0)}\)
(9). For solubility of salt (AgCl ⇌ Ag⁺ + Cl^-)
K_sp = \(\left( \frac{1000\ K}{\Lambda_0} \right)^2\)
(10). For a cell reaction in an electrochemical cell,
Zn + CuSO₄ ⇌ Cu + ZnSO₄
Cell representation ⇒ Zn | Zn²⁺(aq.) || Cu²⁺(aq.) | Cu (Zn is the Anode(-), Cu is the Cathode(+))
(11). For half cell reaction
M → Mⁿ⁺(aq.) + ne^-; E_ox = E_M/Mⁿ⁺
Mⁿ⁺(aq) + ne^- → M; E_red = E_Mⁿ⁺/M
emf of cell, E°_cell = E°_right - E°_left = E°_cathode - E°_anode {R.P. = Reduction potential}
(12). ΔG = -nFE_cell
= -W
= ΔG° + 2.303 RT log Q
ΔG° = -nFE°_cell
E_cell = E°_cell - \(\frac{2.303\,RT}{nF}\) log Q
ΔG = Change in free energy
W = Useful work done
n = Number of electrons exchanged
F = Faraday constant (96500 coulomb)
Q = Reaction quotient
At room temperature (25°C) ⇒ Nernst's equation ⇒ E_cell = E°_cell - \(\frac{0.0591}{n}\) log Q
(13). For electrode concentration cell, (Pt, H₂(P₁) | H⁺ || H₂(P₂), Pt) (P₁ at anode, P₂ at cathode)
E_cell = \(\frac{0.0591}{2}\) log \(\frac{P_1}{P_2}\) (P = Pressure)
For electrolyte concentration cell (Cu | Cu²⁺(C₁) || Cu²⁺(C₂) | Cu) (C₁ at anode(-), C₂ at cathode(+))
E_cell = \(\frac{0.0591}{2}\) log \(\frac{C_2}{C_1}\)
For concentration cells, E°_cell = 0
(14). At equilibrium, E_cell = 0 (as ΔG = 0)
(15). Temperature coefficient (T.C.) = \(\left( \frac{\partial E_{cell}}{\partial T} \right)_P\)
Change in entropy, ΔS = +nF × (T.C.) {ΔH = heat of cell-reaction}
E_cell = \(\left( \frac{-\Delta H}{nF} \right)\) + T.(T.C.)
T.C. > 0 ⇒ Cell-reaction is endothermic and vice-versa.
(16). Faraday's 1^st law of electrolysis
m = Zit
m = mass of substance deposited
Z = electrochemical equivalent
i = current
t = time
Z = \(\frac{\text{Atomic mass}}{n \times F}\)
Faraday's 2^nd law of electrolysis
\(\frac{m_1}{m_2} = \frac{E_1}{E_2}\) (E = equivalent weight)
(17). Oxidation potential for half-cell reaction: M → M⁺ⁿ + ne^-
E_ox = E°_ox - \(\frac{2.303}{nF}\) log [Mⁿ⁺]
Reduction potential for half-cell reaction: Mⁿ⁺ + ne^- → M
E_red = E°_red + \(\frac{2.303\,RT}{nF}\) log [Mⁿ⁺]

9. CHEMICAL KINETICS AND NUCLEAR CHEMISTRY

(1). For a general chemical transformation
nA + mB → pC + qD
Rate = \(\frac{-1}{n}\frac{d[A]}{dt} = \frac{-1}{m}\frac{d[B]}{dt} = +\frac{1}{p}\frac{d[C]}{dt} = \frac{1}{q}\frac{d[D]}{dt}\)
(2). For elementary chemical reaction mA + nB → products
Theoretical rate = \(\frac{dx}{dt}\) = k[A]^m × [B]ⁿ
(3). For a general reaction; aA + bB → Products
Rate = \(\frac{dx}{dt}\) = k[A]^m × [B]ⁿ
Order of reaction w.r.t. A = m, overall order of reaction = (m + n)
Order of reaction w.r.t. B = n
(4). Unit of rate constant = (mole)^1-n (litre)^n-1 time^-1
Where, n = order of reaction
(5). For a zero order reaction; A → B
Rate = \(\frac{-d[A]}{dt}\) = k[A]⁰ = k (constant)
k = \(\frac{[A_0] - [A]}{t}\)
(6). For a first order reaction; A → B
Rate = \(\frac{-d[A]}{dt}\) = k[A]
k = \(\frac{2.303}{t}\) log₁₀ \(\frac{[A]_0}{[A]_t}\) = \(\frac{2.303}{t}\) log₁₀ \(\left( \frac{a}{a - x} \right)\)
(7). For a zero order reaction, t_1/2 = \(\frac{[A]_0}{2k}\)
For a first order reaction, t_1/2 = \(\frac{0.693}{k}\)
For an n^th order reaction, t_1/2 ∝ \(\frac{1}{[A]_0^{\,n-1}}\) (for n ≥ 2)
(8). For a parallel reaction: A → B (rate constant K₁) and A → C (rate constant K₂)
\(\frac{-d[A]}{dt}\) = (k₁ + k₂)[A]
(9). For a first order reaction: A → B + C, a reagent reacts with all A, B and C
k = \(\frac{2.303}{t}\) log₁₀ \(\left( \frac{V_\infty - V_0}{V_\infty - V_t} \right)\) {V = vol. of reagent}
(10). Temperature coefficient = \(\frac{k_{T+10^\circ C}}{k_T}\)
Arrhenius equation, k = Ae^-E_a/RT
log₁₀ \(\frac{k_2}{k_1}\) = \(\frac{E_a}{2.303\,R}\) \(\left( \frac{T_2 - T_1}{T_2 T_1} \right)\)
log₁₀ k = log₁₀ A - \(\frac{E_a}{2.303\,RT}\)
A = Arrhenius's constant
E_a = Activation energy
(12). Binding energy, B.E. = Δm × 931.5 MeV
Δm = mass defect = calculated At. Mass - observed At. Mass
B.E. per nucleon = \(\frac{\text{B.E. (total)}}{\text{mass number}}\)
1 MeV = 9.6 × 10¹⁰ Joule mol^-1
(13). Packing fraction, P.F. = \(\frac{\text{Isotopic atomic mass - mass no.}}{\text{mass number}}\) × 10⁶
(14). In a radioactive decay, N_t = N₀e^-λt
Amount of radioactive substance after 'n' half-life periods: N = \(\left( \frac{1}{2} \right)^n\) N₀
(15). Activity, A_t = A₀e^-λt, A = λN

10. SURFACE CHEMISTRY

(1). Freundlich Adsorption isotherm
\(\frac{x}{m}\) = Kp^1/n; n ≥ 1
(2). Langmuir Adsorption isotherm
θ = \(\frac{K'P_A}{1 + KP_A}\)
Or, \(\frac{x}{m} = \frac{aP}{1 + bP}\) or \(\frac{m}{x} = \frac{1}{aP} + \frac{b}{a}\)
(3). \(\frac{x}{m}\) = KC^1/n; C = Concentration of solute in solution.
(4). Zeta potential, Z = \(\frac{4\pi\eta\mu}{D}\)

11. HYDROGEN

(1) At. Wt. of H = \(\frac{\%\ {}^1_1H \times 1 + \%\ {}^2_1H \times 2 + \%\ {}^3_1H \times 3}{100}\)
(2) Vapour density of a gas = \(\frac{\text{molar mass of gas}}{\text{molar mass of } H_2}\)
LHS and RHS both are unitless
(3). Molecular wt. = 2 × (V.D.)
(4). Vol. Strength of H₂O₂ = Molarity × 11.2
= Normality × 5.6

12. S-BLOCK ELEMENTS

(1) General Electronic Configuration ns^1-2.
(2) Atomic Radii increases down the group.
(3) Hydration enthalpy decreases down the group.
(4). Ionization enthalpy decreases down the group.
(5). On reaction with oxygen give oxide, peroxide and superoxides.
(6) On reaction with water produces hydroxide and hydrogen.
(7). Some important compounds and their general names.

13. P-BLOCK ELEMENTS

(1). In general metallic character, electropositive character, atomic radii, basic character, reducing character decreases on moving left to right in a period and increases down the group.
(2). Some important compound of p-block elements
i. Borax (Tincal): Na₂B₄O₇.10H₂O
ii. Colemanite: Ca₂B₆O₁₁.5H₂O
iii. Kernite: Na₂B₄O₇. 4H₂O
iv. Sassolite or boric acid: H₃BO₃
v. Diborane: B₂H₆
vi. Borazole: B₃N₃H₆
vii. Alumina: Al₂O₃
viii. Lithium aluminium hydride: LiAlH₄
ix. Potash Alum: K₂SO₄. Al₂(SO₄)₃. 24 H₂O

14. COORDINATION COMPOUND

(1). Magnetic moment, μ = \(\sqrt{n(n+2)}\) B.M
(2) Δ₀(CFSE) = [(-4 × n_e^-(t2g)) + (+6 × n_e^-(eg))] Dq
(3). Δ_t(CFSE) = [(+4 × n_e^-(t2g)) + (-6 × n_e^-(eg))] Dq
(4). Δ_t = \(\frac{4}{9}\) Δ₀
(5). For the reaction: M + 4L ⇌ ML₄, overall stability constant of complex (ML₄) is β₄ = \(\frac{[ML_4]}{[M][L]^4}\)
(6). EAN (of metal atom/ion) = Z - O.N. + 2(C.N.)

15. ORGANIC CHEMISTRY

Relations for the estimation of elements in organic compounds.
% of C = \(\frac{12}{44} \times \frac{\text{Mass of } CO_2 \text{ formed}}{\text{Mass of the compound}}\) × 100
% of H = \(\frac{2}{18} \times \frac{\text{Mass of } H_2O \text{ formed}}{\text{Mass of the compound}}\) × 100
% of N (Dumas' method) = \(\frac{28}{22400} \times \frac{\text{Volume of } N_2 \text{ at NTP}}{\text{Mass of compound}}\) × 100
% of N (Kjeldahl's method) = \(\frac{1.4 \times \text{Normality of acid used} \times \text{Volume of acid used}}{\text{Mass of the compound}}\)
% of X (Halogens) = \(\frac{\text{At. mass of X}}{108 + \text{At. mass of X}} \times \frac{\text{Mass of AgX formed}}{\text{Mass of the compound}}\) × 100
% of S = \(\frac{32}{233} \times \frac{\text{Mass of } BaSO_4 \text{ formed}}{\text{Mass of the compound}}\) × 100
% of P = \(\frac{62}{222} \times \frac{\text{Mass of } Mg_2P_2O_7 \text{ formed}}{\text{Mass of the compound}}\) × 100
(1). Inductive effect
(+I effect) CH₃ < C₂H₅ < C₃H₇ < R₂CH < R₃C < -O^-
(-I effect) R₄N⁺ > NO₂ > -CN > SO₃H > COOH > -F > Cl > Br > I > -OR > -OH > -NH₂ > -C₆H₅
(2). Relative basic strength in aqueous medium.

(3). Stability of free radical
Me₃C• (3°) > Me₂CH• (2°) > MeCH₂• (1°) > Me• (methyl)
(4) Heat of hydrogenation of alkenes
1-butene > cis-2-butene > trans-2-butene
(5). Leaving nature in Nucleophilic substitution reaction
ArSO₃^- > ROSO₂^- > CH₃COO^- > CN^- > OH^- > MeO^- > H^- > R^-
(6). Number of product formed during crossed aldol condensation

16. ALCOHOLS, PHENOLS AND ETHERS

Structure of Alcohols:

[Figure: Methanol (alcohol) - the oxygen atom is sp³ hybridised; C-O bond length 142 pm, O-H bond length 96 pm, C-O-H bond angle 108.9°; carbon carries three H atoms]

Preparation of Alcohols

(i) From alkenes
(a) By acid catalysed hydration in accordance with Markownikoff's rule.
>C=C< + H₂O ⇌ (H⁺) >C(H)-C(OH)<
(b) By hydroboration-oxidation
CH₃-CH=CH₂ + (H-BH₂)₂ → (B₂H₆, H₂O₂/OH^-) CH₃CH₂CH₂OH + B(OH)₃
(ii) From carbonyl compounds
(a) By reduction of aldehydes and ketones
R-CHO + H₂ → (Pd) RCH₂-OH
RCOR' → (NaBH₄) R-CH(OH)-R'
(b) By reduction of carboxylic acids and ester
RCOOH → (i) LiAlH₄, (ii) H₂O → RCH₂OH
RCOOR' + H₂ → (Catalyst) RCH₂OH + R'OH
Reduction of aldehyde, ketones and esters with Na and alcohol is called Bouveault-Blanc reduction.

Reaction of carbonyl compound with Grignard Reagent.

HCHO + RMgX → RCH₂OMgX → (H₂O) RCH₂OH + Mg(X)OH
RCHO + R'MgX → R-CH(R')-OMgX → (H₂O, -Mg(OH)X) R-CH(R')-OH
RCOR + R'MgX → R-C(R')(R)-OMgX → (H₂O, -Mg(OH)X) R-C(R')(R)-OH

(iv) Hydrolysis of alkyl halides
R-X + KOH_(aq) → ROH + KX
Ease of hydrolysis of alkyl halides RI > RBr > RCl and 3° > 2° > 1° alkyl halides.
(v) Hydrolysis of ethers
R-O-R + H₂O → (H₂SO₄) 2ROH
(vi) From primary amines by treatment with nitrous acid
RNH₂ + HONO → (NaNO₂ + HCl) ROH + N₂ + H₂O
Methylamine does not give methyl alcohol when treated with HNO₂. It gives CH₃OCH₃ and CH₃ONO.
(vii) By alcoholic fermentation
C₁₂H₂₂O₁₁ (sucrose) + H₂O → (Invertase) C₆H₁₂O₆ (glucose) + C₆H₁₂O₆ (fructose)
C₆H₁₂O₆ (glucose and fructose) → (Zymase) 2C₂H₅OH (ethyl alcohol) + 2CO_2(g)

Preparation of Phenols

(i) From haloarenes
[Figure: Chlorobenzene + NaOH (623 K, 300 atm) → sodium phenoxide (benzene ring with O^-Na⁺) → (HCl) → phenol]
(ii) From benzene sulphonic acid
[Figure: Benzene + Oleum → benzene sulphonic acid (SO₃H on ring) → (i) NaOH, (ii) H⁺ → phenol (OH on ring)]
(iii) From diazonium salts
[Figure: Aniline (NH₂) → (NaNO₂ + HCl, 273-278 K) → benzene diazonium chloride (N₂⁺Cl^-) → (H₂O, warm) → phenol + N₂ + HCl]
(iv) From cumene
[Figure: Cumene (isopropylbenzene) → (O₂) → cumene hydroperoxide (C(CH₃)₂-O-O-H on ring) → (H⁺, H₂O) → phenol + CH₃COCH₃ (acetone)]

Chemical properties of alcohols:

1. Reaction involving cleavage of O-H bond:
Alcohols react as nucleophiles:
(a) Reaction with metals
2R-O-H + 2Na → 2R-O-Na + H₂ (Sodium alkoxide)
(b) Esterification reaction
RO-H (Alcohol) + R'-COOH ⇌ (H⁺) ROCOR' + H₂O
RO-H (Alcohol) + (R'CO₂)O ⇌ (H⁺) ROCOR' + R'COOH
RO-H (Alcohol) + R'COCl → (Pyridine) R-OCOR' + HCl
(b) Reaction with phosphorus halides
ROH + PCl₅ → RCl + POCl₃ + HCl
3ROH + PBr₃ → (P/Br₂) 3RBr + H₃PO₃
3ROH + PI₃ → (P/I₂) 3RI + H₃PO₃
(c) Reaction with thionyl chloride
ROH + SOCl₂ → RCl + SO₂↑ + HCl↑
(c) Dehydration reaction
Alcohol → (Protic acids (conc. H₂SO₄ or H₃PO₄) Or Catalysts (anhyd. ZnCl₂ or alumina)) C=C + H₂O
(d) Oxidation reaction
Alcohol → (Acidified potassium permanganate) Carboxylic acid
(i) Primary Alcohol → (Cu, 573 K, or CrO₃, or PCC) Aldehyde
(ii) Secondary Alcohol → (Cu, 573 K, or CrO₃) Ketone
(iii) Tertiary Alcohol → (Cu, 573 K, or KMnO₄) Alkene

Phenols

Structure of Phenols:

[Figure: Phenol - benzene ring attached to oxygen; C-O bond length 136 pm, C-O-H bond angle 109°, carbon of the ring is sp² hybridised]

Chemical properties of phenols:

(a) Reaction with metals
2 Phenol (C₆H₅OH) + 2Na → 2 Sodium phenoxide (C₆H₅ONa) + H₂
(b) Esterification reaction
Ar-OH (Phenol) + R'-COOH ⇌ (H⁺) Ar-OCOR' + H₂O
Ar-OH (Phenol) + (R'CO)₂O ⇌ (H⁺) Ar-OCOR' + R'COOH
Ar-OH (Phenol) + R'COCl → (Pyridine) ArOCOR' + HCl
(a) Halogenation
Phenol + Br₂ (Excess) → 2,4,6-tribromophenol
Phenol → (Br₂, 0°C, CS₂) o-bromophenol + p-bromophenol
(b) Sulphonation
Phenol → (Conc. H₂SO₄) o-hydroxybenzene sulphonic acid + p-hydroxybenzene sulphonic acid
(c) Nitration
Phenol → (Conc. HNO₃, Conc. H₂SO₄) 2,4,6-trinitrophenol (picric acid)
Phenol → (Dil. HNO₃, Room temperature) o-nitrophenol + p-nitrophenol
(d) Reimer-Tiemann reaction
Phenol → (CHCl₃, Aq.NaOH, 57°C) o-(dichloromethyl)phenoxide (sodium salt, intermediate) → (NaOH) sodium salicylaldehyde (ring with O^-Na⁺ and CHO) → (HCl) salicylaldehyde (chief product)
Phenol → (i) CCl₄, (ii) H⁺, Aq.NaOH → salicylic acid (major) + p-hydroxybenzoic acid (minor)
(ii) Kolbe's reaction
Phenol → (NaOH) sodium phenoxide → (i) CO₂, (ii) H⁺ → 2-hydroxybenzoic acid (salicylic acid)
Salicylic acid + C₆H₅OH → phenyl salicylate (salol)
Salicylic acid + CH₃COCl / (CH₃CO)₂O → acetyl salicylic acid
Salicylic acid + CH₃OH → methyl salicylate (iodex)
(iii) Reaction with zinc dust
Phenol + Zn → Benzene + ZnO
(iv) Oxidation
Phenol → (Na₂Cr₂O₇, H₂SO₄) benzoquinone
(v) Fries rearrangement
Phenyl acetate (C₆H₅OCOCH₃) → (AlCl₃, Δ) o-hydroxyacetophenone + p-hydroxyacetophenone

Ethers

Structure of Ethers

[Figure: Methoxymethane (ether) - the oxygen atom is sp³ hybridised; C-O bond length 141 pm, C-O-C bond angle 111.7°; each carbon carries three H atoms]

Preparation of Ethers

(i) By dehydration of alcohols
2CH₃CH₂-OH (excess) → (H₂SO₄ (conc.), 413 K) CH₃-CH₂-O-CH₂-CH₃ + H₂O
Williamson's Synthesis Only primary alkyl halides when react with sodium alkoxide give ether while tertiary alkyl halides give alkene due to steric hindrance.
CH₃CH₂Br + CH₃CH₂ONa → CH₃CH₂OCH₂CH₃ + NaBr

Chemical Reactions of Ether

R-O-R' + HX → RX + R'OR
The order of reactivity of hydrogen halides is as follows: HI > HBr > HCl
(ii) Halogenation
CH₃CH₂OCH₂CH₃ → (Cl₂, Dark) CH₃CHClOCH₂CH₃ (α-monochloro diethyl ether)
C₂H₅OC₂H₅ + 10Cl₂ (excess) → (hν, light) C₂Cl₅OC₂Cl₅ (perchlorodiethyl ether) + 10HCl
(iii) Reaction with PCl₅
R-O-R + PCl₅ → (Δ) 2RCl + POCl₃
(iv) Reaction with CO
ROR + CO → (BF₃/150°C, 500 atm) RCOOR

Electrophilic Substitution reactions

Anisole (C₆H₅OCH₃) reacts as follows:
Anisole → (Br₂ in CS₂) o-bromoanisole + p-bromoanisole
Anisole → (Conc. HNO₃, Conc. H₂SO₄) o-nitroanisole (minor) + p-nitroanisole (major)
Anisole → (CH₃COCl, Anhy. AlCl₃) 2-methoxyacetophenone + 4-methoxyacetophenone (Friedel-Craft acylation)
Anisole → (CH₃Cl, Anhy. AlCl₃) 2-methoxy toluene (minor) + 4-methoxy toluene (major)

Other conversion reactions:
(a) Phenol to salicylaldehyde
Phenol → (Zn dust) Benzene → (+ CH₃Cl, Anhyd. AlCl₃) Toluene → (Alk. KMnO₄) Benzoic acid → (SOCl₂) Benzoyl chloride (COCl) → (H₂, Pd + BaSO₄ + S, Boiling xylene) Benzaldehyde (CHO)
(b) Phenol to benzene diazonium chloride
Phenol → (Zn dust) Benzene → (Conc. HNO₃ + Conc. H₂SO₄, 333 K) Nitrobenzene → (Sn/HCl, 6[H]) Aniline → (NaNO₂, HCl) Benzene diazonium chloride

Differentiate between organic compounds:

(a) Alcohols and phenols
Phenol on reaction with neutral FeCl₃ gives purple colour whereas alcohols do not give purple colour.
6C₆H₅OH + Fe³⁺ → [Fe(OC₆H₅)₆]^3- (Purple colour) + 6H⁺
(b) Primary, secondary and tertiary alcohols
Lucas reagent test:
ROH + HCl → (conc. HCl + ZnCl₂ / Lucas reagent) RCl + H₂O
If it is a primary alcohol, no turbidity appears at room temperature. Turbidity appears only on heating. If it is a secondary alcohol, turbidity appears in 5 minutes. If it is a tertiary alcohol, turbidity appears immediately.
(c) Methanol and ethanol
Iodoform test: Ethanol when reacted with (I₂ and NaOH) or NaOI gives yellow ppt of iodoform since it has the presence of CH₃-CH(OH)-group.
C₂H₅OH + 4I₂ + 6NaOH → CHI₃ (Yellow ppt) + 5NaI + 5H₂O + HCOONa
CH₃OH + I₂ + NaOH → No yellow ppt

17. ALDEHYDES, KETONES AND CARBOXYLIC ACIDS

Preparation of Aldehydes and Ketones

(i) By oxidation of alcohols
Aldehydes and ketones are generally prepared by oxidation of primary and secondary alcohols, respectively.
RCH₂OH → (CrO₃) RCHO
R-CH(OH)-R' → (CrO₃) R-CO-R'
By dehydrogenation of alcohols
Primary and secondary alcohols give aldehydes and ketones, respectively.
R-CH₂-OH → (Cu, 573 K) RCHO
R-CH(OH)-R' → (Cu, 573 K) R-CO-R'
(iii) By ozonolysis of alkenes
R-CH=CH-R → (i) O₃, (ii) Zn/H₂O → 2RCHO
C₆H₅-CH=C₆H₁₀ (benzylidene cyclohexane) → (i) O₃, (ii) Zn/H₂O → benzaldehyde (C₆H₅CHO) + cyclohexanone
(iv) By hydration of alkynes
CH≡CH (acetylene) + H₂O → (HgSO₄, H₂SO₄) CH₃-CHO (acetaldehyde)
R-C≡CH + H₂O → (HgSO₄, H₂SO₄) R-CO-CH₃ (ketone)

Preparation of Aldehydes

(i) Rosenmund reduction
Benzoyl chloride (C₆H₅COCl) + H₂ → (Pd-BaSO₄) benzaldehyde (C₆H₅CHO)
Formaldehyde cannot be prepared by this method as HCOCl is highly unstable.
(ii) From nitriles
RCN + SnCl₂ + HCl → RCH=NH → (H₃O⁺) RCHO
This reaction is called Stephen reaction.
Alternatively, nitriles are selectively reduced by diisobutylaluminium hydride, [DiBAL-H] to imines which on hydrolysis give aldehydes.
RCN → (i) AlH(i-Bu)₂, (ii) H₂O → RCHO
Similarly, esters can also be reduced to aldehydes with DiBAL-H.
CH₃(CH₂)₃-COOC₂H₅ → (i) DiBAL-H, (ii) H₂O → CH₃(CH₂)₃-CHO
(iii) Etard reaction
Toluene + CrO₂Cl₂ → (CS₂) C₆H₅CH(OCrOHCl₂)₂ → (H₃O⁺) benzaldehyde
Using chromium oxide (CrO₃): Toluene or substituted toluene is converted to benzaldehyde in presence of chromic oxide in acetic anhydride.
Toluene + CrO₃ + (CH₃CO)₂O → (273-283 K) C₆H₅CH(OCOCH₃)₂ → (H₃O⁺, Δ) Benzaldehyde
(iv) Side chain halogenation is followed by hydrolysis of toluene
Toluene → (Cl₂/hν) C₆H₅CHCl₂ → (H₂O, 373 K) C₆H₅CHO
(v) Gattermann-Koch synthesis
Benzene → (CO, HCl; Anhy. AlCl₃ / CuCl) C₆H₅CHO

Preparation of Ketones

(i) From acyl chlorides
2R-Mg-X + CdCl₂ → R₂Cd + 2Mg(X)Cl
2R'-CO-Cl + R₂Cd → 2R'-CO-R + CdCl₂
(ii) From nitriles
CH₃-CH₂-C≡N + C₆H₅MgBr → (Ether) CH₃-CH₂-C(=NMgBr)-C₆H₅ → (H₃O⁺, -NH₃, -Mg(OH)Br) C₂H₅-CO-C₆H₅ (1-Phenylpropanone)
(iii) Friedel-Crafts acylation
Benzene + Ar/R-CO-Cl → (Anhy. AlCl₃) C₆H₅-CO-Ar/R
(iv) Oppenauer oxidation
R₂CHOH (2° alcohol) + (CH₃)₂C=O → ((CH₃)₃CO)₃Al → R₂C=O (ketone) + (CH₃)₂CHOH (iso-propyl alcohol)

Chemical Reactions of Aldehydes and Ketones

(i) Addition of hydrogen cyanide
>C=O + HCN → >C(OH)(CN) (cyanohydrin)
(ii) Addition of sodium hydrogen sulphite
>C=O + NaHSO₃ ⇌ >C(OH)(OSO₂Na) (white crystalline solid)
R-CHO + R'OH (HCl gas) ⇌ [R-CH(OR')(OH)] (Hemiacetal) ⇌ (R'OH, H⁺) R-CH(OR')₂ (Acetal) + H₂O
R₂C=O + HOCH₂-CH₂OH → (HCl gas, dil HCl) R₂C(-O-CH₂-CH₂-O-) + H₂O (Ethylene glycol ketal)
(iii) Addition of Grignard reagent (RMgX) to form alcohol
>C=O + R^δ--Mg^δ+-X → [>C(R)-O^-Mg⁺-X] (Adduct) → (H₂O) >C(R)-OH + Mg(OH)X
(iv) Addition of ammonia and its derivatives
>C=O + H₂N-Z ⇌ [>C(OH)(NZH)] → (H₂O) >C=N-Z + H₂O
Z = Alkyl, aryl, OH, NH₂, C₆H₅NH, NHCONH₂, etc

Reduction

(1). Clemmensen reduction
>C=O → (Zn-Hg, HCl) >CH₂ + H₂O
(2). Wolff-Kishner reduction
>C=O + H₂N-NH₂ (-H₂O) → >C=N-NH₂ → (KOH/ethylene glycol, Δ) >CH₂ + N₂
(3). Oxidation
(i) Aldehydes are oxidized to acids in presence of mild oxidizing agents HNO₃, K₂Cr₂O₇, KMnO₄
R-CHO → [O] R-COOH
(ii) Ketones are oxidized under drastic conditions i.e. with powerful oxidizing agents like HNO₃, K₂Cr₂O₇/H₂SO₄, KMnO₄/H₂SO₄ at higher temperature.
R-CH₂-CO-CH₂-R' → [O] R-COOH + R'-CH₂COOH (By cleavage of C₁-C₂ bond) + R-CH₂COOH + R'-COOH (By cleavage of C₂-C₃ bond)
(iii) Haloform reaction:
R-CO-CH₃ → (NaOX) R-COONa + CHX₃ (X = Cl, Br, I)
(v) Aldol condensation
2CH₃-CHO (ethanal) → (Dil NaOH) CH₃CH(OH)-CH₂-CHO (3-hydroxybutanal, aldol) → (-H₂O, Δ) CH₃-CH=CHCHO (but-2-enal)
2CH₃COCH₃ (propanone) → (Ba(OH)₂) CH₃-C(CH₃)(OH)-CH₂COCH₃ (ketol) → (Δ, -H₂O) CH₃-C(CH₃)=CH-COCH₃ (4-methylpent-3-en-2-one, mesityl oxide)

Cross aldol condensation

Base catalysed crossed aldol condensation between an aromatic aldehyde and an aliphatic aldehyde or ketone is called Claisen-Schmidt condensation or Claisen reaction.
CH₃-CHO + CH₃CH₂CHO → (i) NaOH, (ii) Δ
Self aldol products: CH₃CH=CH-CHO (but-2-enal) + CH₃CH₂CH=C(CH₃)-CHO (2-methylpent-2-enal)
Cross aldol products: CH₃-CH₂-CH=CH-CHO (pent-2-enal) + CH₃-CH=C(CH₃)-CHO (2-methylbut-2-enal)

Cannizzaro reaction

HCHO (Formaldehyde) + HCHO + Conc. KOH → CH₃OH (Methanol) + HCOOK (Potassium formate)
2 C₆H₅CHO (Benzaldehyde) + Conc. NaOH → C₆H₅CH₂OH (Benzyl alcohol) + C₆H₅COONa (Sodium benzoate)

Test to distinguish aldehydes and ketones:

(1) Tollen's test: When an aldehyde is heated with Tollen's reagent it forms silver mirror.
Tollen's reagent is ammoniacal solution of AgNO₃
RCHO + 2[Ag(NH₃)₂]⁺ + 3OH^- → RCOO^- + 2Ag + 2H₂O + 4NH₃
Ketones do not form silver mirror and hence do not give this test.
(2) Fehling's test: When an aldehyde is heated with Fehling's reagent it forms reddish brown precipitates of cuprous oxide.
Fehling's reagent: Fehling solution A (aqueous solution of CuSO₄) + Fehling solution B (alkaline solution of sodium potassium tartarate)
R-CHO + 2Cu²⁺ + 5OH^- → RCOO^- + Cu₂O (Red-Brown ppt) + 3H₂O
Ketones do not give this test.

Carboxylic Acids

Methods of Preparation of carboxylic Acids

From primary alcohols and aldehydes
(a) RCH₂OH → (alkaline KMnO₄/H₃O⁺) RCOOH
(b) RCH₂OH → (CrO₃-H₂SO₄) RCOOH

From aldehydes
(a) RCHO + 2[Ag(NH₃)₂]⁺ + 3OH^- → RCOO^- + 2Ag + 2H₂O + 4NH₃
(b) R-CHO + 2Cu²⁺ + 5OH^- → RCOO^- + Cu₂O + 3H₂O

From alkyl benzenes
Alkylbenzene (C₆H₅-R) → (KMnO₄, KOH, Heat) C₆H₅COOK → (H₃O⁺) Benzoic acid (C₆H₅COOH)

From acid derivatives

All acid derivatives like amides (RCONH₂), acid halides (RCOCl), esters (RCOOR'), acid anhydrides (RCO-O-COR) on hydrolysis give carboxylic acids. All acid derivatives break from RCO⁺.
RCOZ → (Dil. HCl or dil. NaOH) RCOOH
Z = -NH₂, -X (X = Cl, Br, I), OR', RCOO- etc.
Ease of hydrolysis: RCOCl > (RCO)₂O > RCOOR' > RCONH₂

From nitriles and amides
R-CN → (H⁺ or OH^-/H₂O) R-CO-NH₂ → (H⁺ or OH^-/Δ) RCOOH

From alkenes
Suitably substituted alkenes are oxidized to carboxylic acids on oxidation with acidic potassium permanganate or acidic potassium dichromate.
(a) R-CH=CH-R → (KMnO₄/H⁺) 2R-COOH
(b) R-CH=CH-R₁ → (KMnO₄/H⁺) R-COOH + R₁-COOH

From Grignard reagents
R-Mg-X + O=C=O → (Dry ether) R-CO-O^-MgX⁺ → (H₃O⁺) RCOOH

By heating germinal dicarboxylic acids
R-CH(COOH)₂ → (Δ) R-CH₂-COOH + CO₂

From alkynes
R-C≡C-R → (i) O₃, (ii) H₂O₂ or KMnO₄/OH^-, Δ → 2RCOOH

Reactions of Carboxylic acids

Formation of anhydride
CH₃-COOH + HOOC-CH₃ → (H⁺, Δ or P₂O₅, Δ, -H₂O) CH₃-CO-O-CO-CH₃

Esterification
RCOOH + R'OH ⇌ (H⁺) RCOOR' + H₂O

Reactions with PCl₅, PCl₃ and SOCl₂
RCOOH + PCl₅ → RCOCl + POCl₃ + HCl
3RCOOH + PCl₃ → 3RCOCl + H₃PO₃
RCOOH + SOCl₂ → RCOCl + SO₂ + HCl

Reaction with ammonia (NH₃)
Carboxylic acids react with ammonia to give ammonium salt which on further heating at high temperature gives amides.
(a) CH₃COOH + NH₃ ⇌ CH₃COO^-NH₄⁺ (Ammonium acetate) → (Δ/-H₂O) CH₃CONH₂ (Acetamide)
(b) C₆H₅COOH + NH₃ ⇌ C₆H₅COO^-NH₄⁺ (Ammonium benzoate) → (Δ, -H₂O) C₆H₅CONH₂ (Benzamide)

Chemical reactions involving -COOH group

(a) Reduction
RCOOH → (i) LiAlH₄/ether or B₂H₆, (ii) H₃O⁺ → R-CH₂-OH
(b) Decarboxylation
RCOONa → (NaOH, CaO (Ratio 3:1), Δ) R-H + Na₂CO₃

Substitution reactions in the hydrocarbon part
Hell-Volhard-Zelinsky reaction
R-CH₂-COOH → (X₂/Red Phosphorus/H₂O) R-CH(X)-COOH (X = Cl, Br; α-Halocarboxylic acid)
Arndt-Eistert reaction
RCOOH → (PCl₅) RCOCl → (CH₂N₂) RCOCHN₂ (diazo ketone) → (HOH) RCH₂COOH
Reducing property
HCOOH + HgCl₂ → Hg + 2HCl + CO₂
Electrophilic substitution reactions of aromatic acids
Benzoic acid → (Conc. HNO₃ + Conc. H₂SO₄) m-Nitrobenzoic acid
Benzoic acid → (Br₂/FeBr₃) m-Bromobenzoic acid
Benzoic acid → (Conc. H₂SO₄) 3-sulphonic benzoic acid

18. AMINES

Methods of Preparation of Amines

(i) By reduction of nitro compounds:
Nitro compounds can be catalytically reduced by passing hydrogen gas in presence of Raney Ni, finely divided Pt or Pd as catalyst at room temperature.
(a) R-NO₂ + 3H₂ → (Ni, Pt or Pd) R-NH₂ + 2H₂O
(b) Ar-NO₂ + 3H₂ → (Ni, Pt or Pd) Ar-NH₂ + 2H₂O
Nitro compounds can also be reduced with active metals such as Fe, Sn, Zn etc. with conc. HCl.
(a) R-NO₂ + 3H₂ → (Sn/HCl or Fe/HCl) R-NH₂ + 2H₂O
(b) Ar-NO₂ + 3H₂ → (Sn/HCl or Fe/HCl) Ar-NH₂ + 2H₂O
(ii) By Hoffmann's method (Ammonolysis of alkyl halides):
RNH₂ (1°) → (RX) R₂NH (2°) → (RX) R₃N (3°) → (RX) R₄N⁺X^- (Quaternary ammonium salt)
The free amine can be obtained from the ammonium salt by treatment with a strong base:
(a) NH₃ + RX → RNH₃⁺X^- → (NaOH) RNH₂ (1° amine) + H₂O + Na⁺X^-
(b) RNH₂ + RX → R₂NH₂⁺X^- → (NaOH) R₂NH (2° amine) + H₂O + Na⁺X^-
(c) R₂NH + RX → R₃NH⁺X^- → (NaOH) R₃N (3° amine) + H₂O + Na⁺X^-
Order of reactivity of halides is: RI > RBr > RCl
(iii) By reduction of nitriles:
Nitriles can be reduced to amines using H₂/Ni, LiAlH₄ or Na(Hg)/C₂H₅OH
R-C≡N → (H₂/Ni or Na(Hg)/C₂H₅OH or LiAlH₄) R-CH₂-NH₂
(iv) By reduction of amides:
Amides are reduced to corresponding amines by LiAlH₄
R-CO-NH₂ → (LiAlH₄/H₂O) R-CH₂-NH₂
(v) Gabriel's phthalimide reaction
Phthalimide → (KOH (Alc.)) potassium phthalimide → (RX) N-alkyl phthalimide → (KOH) potassium phthalate (C₆H₄(COOK)₂) + RNH₂ (1° amine)
(vi) Hofmann bromamide degradation reaction
R-CO-NH₂ + Br₂ + 4NaOH → RNH₂ + Na₂CO₃ + 2NaBr + 2H₂O

Reactions of Amines

(i) Alkylation
C₂H₅NH₂ + C₂H₅Br → (-HBr) (C₂H₅)₂NH → (C₂H₅Br, -HBr) (C₂H₅)₃N → (C₂H₅Br) (C₂H₅)₄N⁺Br^-
Aniline (C₆H₅NH₂) → (C₂H₅Cl) C₆H₅NHC₂H₅ → (-HBr, C₂H₅Br) C₆H₅N(C₂H₅)₂ → (C₂H₅Br) C₆H₅N⁺(C₂H₅)₃Br^- (triethylanilinium bromide)
(ii) Acylation
C₂H₅-NH₂ + CH₃COCl → (Base) C₂H₅-NH-CO-CH₃ + HCl
C₂H₅-NH₂ + CH₃-CO-O-CO-CH₃ → C₂H₅-NH-CO-CH₃ + CH₃COOH
(iii) Benzoylation
CH₃NH₂ + C₆H₅COCl → (Pyridine) CH₃NHCOC₆H₅ + HCl
Benzoylation of aniline is known as Schotten Baumann reaction.
(iv) Carbylamine reaction [only by 1° amines]
R-NH₂ + CHCl₃ + 3KOH → (Heat) R-N≡C (isocyanide, a bad smelling compound) + 3KCl + 3H₂O
Methyl isocyanate gas (CH₃-N=C=O) was responsible for Bhopal gas tragedy in December 1984.
(v) Reaction with nitrous acid
RNH₂ + HNO₂ → (NaNO₂ + HCl) [RN₂⁺Cl^-] → (H₂O) ROH + N₂ + HCl
Quantitative evolution of nitrogen is used in estimation of amino acids and proteins.
C₆H₅-NH₂ → (NaNO₂ + 2HCl, 273-278 K) C₆H₅N₂⁺Cl^- + NaCl + 2H₂O

Reaction with aryl sulphonyl chloride [Hinsberg reagent]

C₆H₅SO₂Cl + H-NH-R (1° amine) → C₆H₅SO₂-NH-R (N-Alkylbenzene sulphonamide, soluble in alkali) + HCl
C₆H₅SO₂Cl + H-NR₂ (2° amine) → C₆H₅SO₂-NR₂ (N,N-Dialkylbenzene sulphonamide, insoluble in alkali) + HCl
C₆H₅SO₂Cl + NR₃ (3° amine) → No reaction

Reaction with aldehydes

Schiff base is obtained.
C₆H₅NH₂ + OHCC₆H₅ (benzaldehyde) → (ZnCl₂, Δ, -H₂O) C₆H₅N=CHC₆H₅ (benzylidene aniline, Schiff base)

Electrophilic substitution reactions

Aniline + 3Br₂ → (Br₂/H₂O) 2,4,6-Tribromoaniline (white ppt) + 3HBr

Nitration

(a) Under strongly acidic medium aniline gets protonated to form anilinium ion, which is deactivating group and is meta directing. Hence m-nitroaniline is also formed in 47 % along with ortho and para products.
Aniline → (HNO₃, H₂SO₄, 288 K) p-nitroaniline (51%) + m-nitroaniline (47%) + o-nitroaniline (2%)
Aromatic amines cannot be nitrated directly because HNO₃ being a strong oxidizing agent oxidizes it forming black mass.
(b) Nitration by protecting the -NH₂ group by acetylation reaction with acetic anhydride:
Aniline → ((CH₃CO)₂O, Pyridine) Acetanilide (NHCOCH₃) → (HNO₃, H₂SO₄, 288 K) p-Nitroacetanilide → (OH^- or H⁺) p-Nitroaniline
(c) Sulphonation: On sulphonation, aniline gives sulphanilic acid, as the major product.
Aniline → (H₂SO₄) Anilinium hydrogensulphate → (453-473 K) Sulphanilic acid ⇌ Zwitter ion

Oxidation

Benzene Diazonium Chloride (C₆H₅N₂⁺Cl^-)

Preparation (Diazotisation reaction)
C₆H₅NH₂ + NaNO₂ + 2HCl → (273-278 K) C₆H₅N=N-Cl + NaCl + 2H₂O

Chemical reactions

C₆H₅N₂⁺Cl^- → (Cu⁺, H₃PO₂/H₂O) C₆H₆ + N₂↑ + H₃PO₃ + HCl
C₆H₅N₂⁺Cl^- → (CH₃CH₂OH) C₆H₆ + N₂ + HCl + CH₃CHO (Deamination)
C₆H₅N₂⁺Cl^- → (CuBr/HBr) C₆H₅Br + N₂ (bromobenzene)
(a) Reactions involving displacement of nitrogen:
ArN₂⁺Cl^- → (CuCl/HCl) ArCl + N₂
ArN₂⁺Cl^- → (CuBr/HBr) ArBr + N₂
ArN₂⁺Cl^- → (CuCN/KCN) ArCN + N₂
ArN₂⁺Cl^- → (Cu/HCl) ArCl + N₂ + CuCl
ArN₂⁺Cl^- → (Cu/HBr) ArBr + N₂ + CuBr
ArN₂⁺Cl^- → (KI) ArI + KCl + N₂
ArN₂⁺Cl^- → (HBF₄) ArN₂⁺BF₄^- → (Δ) Ar-F + BF₃ + N₂
ArN₂⁺Cl^- → (H₃PO₂ + H₂O) ArH + N₂ + H₃PO₃ + HCl
ArN₂⁺Cl^- → (H₂O) ArOH + N₂ + HCl
ArN₂⁺Cl^- → (CH₃CH₂OH) ArH + N₂ + CH₃CHO + HCl
ArN₂⁺Cl^- → (HBF₄) C₆H₅N₂⁺BF₄^- → (NaNO₂, Cu, Δ) C₆H₅NO₂ + N₂ + NaBF₄

Azo coupling reactions

C₆H₅N₂⁺Cl^- + H-C₆H₄-OH → (OH^-) C₆H₅-N=N-C₆H₄-OH + Cl^- + H₂O (p-Hydroxyazobenzene, orange dye)
C₆H₅N₂⁺Cl^- + H-C₆H₄-NH₂ → (OH^-) C₆H₅-N=N-C₆H₄-NH₂ + Cl^- + H₂O (p-Aminoazobenzene, yellow dye)

Alkyl Cyanides

Methods of Preparation

(i) From alkyl halides
RX + KCN_(alc) → (100°C) RCN (major) + RNC
(ii) From acid amides
RCONH₂ → (P₂O₅, Δ, -H₂O) RC≡N

Reactions of Alkyl Cyanides

(i) Hydrolysis
RCN → (H₂O, Alk H₂O₂ (partial hydrolysis)) RCONH₂ (amide) → (H₂O, H⁺) RCOOH (carboxylic acid) + NH₃
(ii) Reduction
RCN + 4[H] → (Na + C₂H₅OH) RCH₂NH₂
RCN + 4[H] → (LiAlH₄) RCH₂NH₂ (Mendius reduction)
RCN → (SnCl₂/HCl) RCH=NH.HCl (imine hydrochloride) → (H₂O) RCHO (aldehyde) + NH₄Cl
(iii) Reaction with Grignard reagent
RCN + R'MgX → (Ether) R-C(R')=NMgX → (2H₂O) R-CO-R'

Alkyl isocyanides

Methods of Preparation

(a) From alkyl halides
R-X + AgCN → (C₂H₅OH, Δ) RNC (major) + RCN
(b) Carbylamine reaction
RNH₂ + CHCl₃ + 3KOH_(alc) → (Δ) RNC + 3KCl + 3H₂O
(c) From N-alkyl formamide
R-NH-CHO → (POCl₃, Pyridine) R-N≡C + H₂O

Reactions of Alkyl isocyanides

Hydrolysis
R-N≡C + 2H₂O → (H⁺) RNH₂ + HCOOH
(ii) Reduction
RN≡C + 4[H] → (Na/C₂H₅OH or Ni or Pt) RNHCH₃ (2° amine)
(iii) Addition reaction
Due to the presence of unshared pair of electrons on C atom, alkyl isocyanides give addition reaction.
RNC + S → RNCS
RNC + HgO → RNCO + Hg
RNC + O₃ → RNCO
(iv) Isomerisation At 250°C, it isomerizes to nitrile.
RNC → (Δ) RCN

Nitro Compounds

Methods of Preparation

(i) From alkyl halides
RX + AgNO₂ → (Δ) RNO₂ + AgX
(ii) Nitration: Nitrating mixture is conc HNO₃ + conc H₂SO₄
Benzene + Conc. HNO₃ → (Conc. H₂SO₄) Nitrobenzene (C₆H₅NO₂)

Reactions of Nitro Compounds

Reduction
With Sn/HCl or catalytic hydrogenation, nitroalkanes are reduced to amines.
RNO₂ + 6[H] → (Sn/HCl) R-NH₂ + 2H₂O
If neutral reducing agent like Zn dust + NH₄Cl is used, hydroxylamines are obtained as major product.
RNO₂ + 4[H] → (Zn + NH₄Cl) R-NHOH (N-alkylhydroxylamine) + H₂O
In the presence of (NH₄)₂S or Na₂S, selective reduction takes place.
m-Dinitrobenzene + 3(NH₄)₂S → m-Nitroaniline + 6NH₃ + 2H₂O + 3S (Zinin reduction)
Nitrobenzene gives different products with different reagents and in different mediums.

Action of HNO₂

1° nitroalkane gives nitrolic acid which gives red colour with NaOH.
RCH₂NO₂ → (HNO₂, -H₂O) RC(NO₂)=NOH (nitrolic acid) → (NaOH) RC(NO₂)=NONa (red)
2° nitroalkanes give pseudonitrol with HNO₂
R₂CH(NO₂) → (HNO₂, -H₂O) R₂C(NO)(NO₂) (Pseudonitrol) → (NaOH) Blue

Nef carbonyl synthesis

R-CH₂NO₂ → (NaOH) R-CH=N(→O)-O^-Na⁺ → (50% H₂SO₄) R-CH=O (aldehyde)

Electrophilic substitution On nitration
Nitrobenzene → (Fuming HNO₃, H₂SO₄, Δ) m-dinitrobenzene

Nucleophilic substitution reaction -NO₂ group activates the ring towards nucleophilic substitution.
Nitrobenzene + OH^- (NaOH, Slow) → intermediate (carbanion with OH and H on the ring carbon ortho to NO₂) → (Fast, -H^-) o-nitrophenol
m-Dinitrobenzene → (K₃[Fe(CN)₆], NaOH) 2,6-dinitrophenol + 2,4-dinitrophenol
p-Bromonitrobenzene → (KCN, C₂H₅OH) m-Bromobenzonitrile (von Richter reaction)

19. HALOALKANES AND HALOARENES

General Methods of Preparation of Haloalkanes

From Alcohols
R-OH (alcohol) → (HCl + Anhy. ZnCl₂ (Lucas reagent)) R-Cl + H₂O (Groove's process)
R-OH → (NaBr + H₂SO₄, Reflux) R-Br + H₂O
R-OH → (PX₃) 3R-X + H₃PO₃
R-OH → (PCl₅) R-Cl + POCl₃ + HCl
R-OH → (Pyridine, SOCl₂) R-Cl + SO₂↑ + HCl↑ (Darzen procedure)

Free Radical Halogenation of Alkanes
CH₃CH₂CH₂CH₃ → (Cl₂, UV light or Heat) CH₃CH₂CH₂CH₂Cl + CH₃CH₂CHClCH₃

Addition of hydrogen Halides on Alkenes
>C-C=C< + HBr → >C-C(Br)-C< (Markovnikov addition, e.g. 2-bromopropane from propene)
>C-C=C< + HBr → (Organic peroxide) >C-C-C-Br (anti-Markovnikov addition)

(i) Halogen Exchange method:
R-X + NaI → R-I + NaX (Finkelstein reaction)
R-Br + AgF → R-F + AgBr (Swarts reaction)

Hunsdiecker Reaction
CH₃COOAg + Br₂ → (CCl₄) CH₃Br + AgBr + CO₂

Preparation of haloarenes:
(a) By electrophilic substitution reaction:
Toluene + X₂ → (Fe, dark) o-halotoluene + p-halotoluene
Toluene + X₂ → (383 K, sunlight) benzyl halide (C₆H₅CH₂X, side chain substitution)
(b) Sandmeyer's reaction:
Aniline → (NaNO₂ + HX, 273-278 K) Benzene diazonium halide (C₆H₅N₂⁺X^-) → (Cu₂X₂) Aryl halide + N₂ (X = Cl, Br)
(c) Gattermann reaction:
C₆H₅N₂⁺X^- → (Cu, HX) Aryl halide + N₂ (X = Cl, Br)
(d) From Diazonium Chloride:
C₆H₅N₂⁺X^- → (KI, warm) Iodobenzene
(e) Balz-Schiemann reaction:
C₆H₅N₂⁺X^- + HBF₄ → [C₆H₅N₂⁺BF₄^-] → Fluorobenzene
Nucleophilic Substitution Reactions
Nu^- + >C^δ+-X^δ- → >C-Nu + X^-
C₂H₅-Br → (KOH (aq)) C₂H₅OH + KBr
C₂H₅-Br → (NH₃) C₂H₅NH₂, (C₂H₅)₂NH, (C₂H₅)₃N, (C₂H₅)₄N⁺Br^- (Hofmann ammonolysis)
C₂H₅-Br → (KCN) C₂H₅CN + KBr
C₂H₅-Br → (AgCN) C₂H₅NC + AgBr
C₂H₅-Br → (KNO₂) C₂H₅-ONO (ethyl nitrite) + KBr
C₂H₅-Br → (AgNO₂) C₂H₅NO₂ (nitroethane) + AgBr
C₂H₅-Br → (R'ONa, Δ) C₂H₅-O-R' + NaBr (Williamson's synthesis)
C₂H₅-Br → (Na-C≡C-H, Δ) C₂H₅-C≡CH + NaBr
C₂H₅-Br → (R'COOAg, Δ) C₂H₅-O-CO-R' + AgBr

2. Elimination Reactions

Dehydrohalogenation is a β-elimination reaction in which halogen is from α-carbon atom and the hydrogen from the β-carbon according to Saytzeff rule, e.g.
CH₃-CH₂-CHBr-CH₃ → (Alc. KOH, -KBr, -H₂O) CH₃-CH=CH-CH₃ (but-2-ene, major) + CH₃CH₂CH=CH₂ (butene-1, minor)

Reduction

C₂H₅-Br + H₂ → (Ni, 575 K) C₂H₆ + HBr
C₂H₅I + HI → (Red P, 420 K) C₂H₆ + I₂

Reaction with Metals

(i) Wurtz reaction
RX + 2Na + XR → (Dry ether) R-R (alkane) + 2NaX
(ii) Wurtz-Fittig reaction
C₆H₅-Cl + 2Na + Cl-CH₃ → (Dry ether) C₆H₅-CH₃ + 2NaCl
(iii) Reaction with Mg
C₂H₅Br + Mg → (Dry ether) C₂H₅-Mg-Br (Grignard's reagent)

Isomerisation

CH₃CH₂CH₂-Cl → (573 K or anhy. AlCl₃) CH₃-CHCl-CH₃

Chemical properties of haloarenes:

(a) Dow's Process
Chlorobenzene → (i) NaOH, 623 K, 300 atm, (ii) H⁺ → Phenol

Electrophilic substitution Reactions

(b) With halogens
Chlorobenzene + Cl₂ → (Anhyd. FeCl₃) 1,4-Dichlorobenzene (Major) + 1,2-Dichlorobenzene (Minor)
(c) With conc. sulphuric acid and nitric acid
Chlorobenzene → (HNO₃, conc. H₂SO₄) 1-Chloro-2-nitrobenzene (Minor) + 1-Chloro-4-nitrobenzene (Major)
(d) On heating with conc. sulphuric acid
Chlorobenzene → (conc. H₂SO₄, Δ) 2-Chlorobenzene sulfonic acid (Minor) + 4-Chlorobenzene sulfonic acid (Major)
(e) With methyl chloride
Chlorobenzene + CH₃Cl → (Anhyd. AlCl₃) 1-Chloro-2-methylbenzene (Minor) + 1-Chloro-4-methylbenzene (Major)
(f) With acetyl chloride
Chlorobenzene + CH₃COCl → (Anhyd. AlCl₃) 2-Chloroacetophenone (Minor) + 4-Chloroacetophenone (Major)

(i) Other conversions:

R-X + KCN → R-CN + KX
R-CN → (Na, C₂H₅OH or LiAlH₄ or Ni/H₂) R-CH₂NH₂ → (HONO) RCH₂OH
R-CN → (H₃O⁺) R-COOH → (NH₃) R-CONH₂
R-COOH → (LiAlH₄) RCH₂OH
R-COOH → (PCl₅ or PCl₃ or SOCl₂) R-COCl
R-X + Mg → (Dry ether) RMgX
RMgX + CO₂ → RCOOH
RMgX + HCHO → Primary alcohol
RMgX + RCHO → Secondary alcohol
RMgX + R-CO-R → Tertiary alcohol

20. HYDROCARBONS

Classification of Hydrocarbons:

[Figure: Classification chart. HYDROCARBON branches into Acyclic or Aliphatic (Open chain), which has Alkanes, Alkenes, Alkynes; and Carbocyclic or Cyclic, which branches into Alicyclic (with Cycloalkanes, Cycloalkenes, Cycloalkynes) and Aromatic]

Alkanes

Preparation of Alkanes

(1) Wurtz reaction:
2CH₃CH₂Br + 2Na → (Dry ether) CH₃CH₂CH₂CH₃ + 2NaBr
Frankland reaction
RX + Zn + RX → R-R + ZnX₂
(2) From Grignard reagent (RMgX)
RMgX + HOH → RH + Mg(OH)X
RMgX + R'OH → RH + Mg(OR')X
RMgX + R'NH₂ → RH + Mg(NHR')X
(3) From unsaturated hydrocarbons:
Sabatier-Senderens reduction
R-CH=CH₂ + H₂ → (Ni/Δ) R-CH₂-CH₃
R-C≡CH + 2H₂ → (Ni/Δ) R-CH₂-CH₃
(4) From carboxylic acids
Decarboxylation:
CH₃COO^-Na⁺ (Sodium ethanoate) + NaOH → (CaO, Δ) CH₄ + Na₂CO₃
Kolbe's electrolytic method:
2CH₃COO^-Na⁺ (Sodium acetate) + 2H₂O → (Electrolysis) CH₃-CH₃ + 2CO₂ + H₂ + 2NaOH

Reactions

Combustion:
CH₄ + 2O₂ → CO₂ + 2H₂O, ΔH = -217.0 kcal/mole
Oxidation:
2CH₄ + O₂ → (Cu, 573 K) 2CH₃OH
CH₄ + O₂ → (Mo₂O₃) HCHO (Methanal) + H₂O
Substitution:
Halogenation:
CH₄ + Cl₂ → (UV) CH₃Cl + HCl
CH₃Cl → (UV) CH₂Cl₂ → (UV) CHCl₃ → (UV) CCl₄
(i) The reactivity of Halogens: F₂ > Cl₂ > Br₂ > I₂
(ii) The rate of replacement of Hydrogens of alkanes is: 3° > 2° > 1°
n-Butane (CH₃CH₂CH₂CH₃) → (Cl₂, hν) CH₃CH₂CH₂CH₂Cl + CH₃CH₂CHClCH₃
Isobutane ((CH₃)₃CH) → (Cl₂, hν) (CH₃)₃C-Cl (36%, 3°) + (CH₃)₂CH-CH₂Cl (64%, 1°)
Nitration
CH₃CH₂CH₃ → (450°C, Conc. HNO₃) CH₃CH₂CH₂NO₂ (25 %) + CH₃CHNO₂CH₃ (40 %) + CH₃CH₂NO₂ (10 %) + CH₃NO₂ (25 %)
Sulphonation: replacement of hydrogen atom of alkane by -SO₃H group.
Isobutane → (oleum, Δ) tert-butyl sulphonic acid ((CH₃)₃C-SO₃H)
Aromatization:
Hexane (H₃C(CH₂)₄CH₃) → (Cr₂O₃, 773 K, 10-20 atm) Benzene
(6) Thermal decomposition or Pyrolysis or cracking or Fragmentation: when higher alkanes are heated at high temp (about 700 - 800 K) in the presence of alumina or silica catalysts, the alkanes break down to lower alkenes and alkanes.
CH₃-CH₂-CH₃ → CH₃-CH=CH₂ + CH₃-CH₃ + C₂H₄ + CH₄
(7) Action of steam: Catalyst: nickel, alumina Al₂O₃
CH₄ + H₂O (Steam) → (1000°C) CO + 3H₂
Isomerization
n-Hexane (CH₃(CH₂)₄CH₃) → (Anhy. AlCl₃/HCl) 2-Methylpentane (CH₃CH(CH₃)-(CH₂)₂-CH₃) + 3-Methylpentane (CH₃CH₂-CH(CH₃)-CH₂-CH₃)

Alkenes

Preparation:

1. From Alkynes: Alkynes on partial reduction with partially deactivated palladised charcoal known as Lindlar's catalyst give alkenes.
CH≡CH (Ethyne) + H₂ → (Pd/C) CH₂=CH₂ (Ethene)
2. From Haloalkanes: dehydrohalogenation (E₂ or 1, 2-elimination or Beta-elimination)
CH₂(H)-CH₂Br → (Alc.KOH, Δ) CH₂=CH₂ + KBr + H₂O
3. From Dihaloalkanes: Dehalogenation
BrCH₂-CH₂Br → (Zn/HOAC) CH₂=CH₂ + ZnBr₂
BrCH₂-CH₂Br → (NaI, acetone) CH₂=CH₂ + I₂ + 2NaBr
4. From Alcohols: Dehydration (E1 elimination)
CH₃CH₂CH₂OH → (Conc. H₂SO₄, 160°) CH₃CH=CH₂ + H₂O
CH₃CH₂CH₂CH₂OH → (Al₂O₃, 300°C) CH₃CH₂CH=CH₂

Reactions of Alkenes

(1) Addition Reaction: Alkene show electrophilic addition reaction.
1. Addition of Hydrogen:
RCH=CH₂ → (H₂/Ni) RCH₂CH₃
2. Addition of Halogens:
CH₂=CH₂ + Br₂ → (CCl₄ Solvent) BrCH₂-CH₂Br
CH₂=CH₂ + Br₂ (Brown colour) → (H₂O Solvent) Br-CH₂-CH₂-OH (Colourless) + HBr
3. Addition of hydrogen halides
Addition reaction of HBr to symmetrical alkenes
CH₂=CH₂ + H-Br → CH₃-CH₂-Br
Addition reaction of HBr to unsymmetrical alkenes takes place according to Markovnikov Rule

Markownikov rule: negative part of the addendum (adding molecule) gets attached to that carbon atom which possesses lesser number of hydrogen atoms. E.g.
(CH₃)₂C=CH₂ + H⁺ at position (1) → (CH₃)₃C⁺ (3°, more stable cation) → (Br^-) (CH₃)₃C-Br (Major Product)
(CH₃)₂C=CH₂ + H⁺ at position (2) → (CH₃)₂CH-CH₂⁺ (1°, less stable cation) → (Br^-) (CH₃)₂CH-CH₂Br (Minor Product)

Peroxide effect or Kharasch (Anti Markownikoff's addition): In 1933 Kharasch and Mayo observed that when HBr is added to an unsymmetrical double bond in the presence of organic peroxide, the reaction take places opposite to the markovnikov rule.
CH₃-CH=CH₂ → (HBr, Peroxide) CH₃-CH₂-CH₂Br (Propyl bromide)

4. Addition of water (Hydration): Acid catalyzed addition of water
CH₃-CH=CH₂ + H₂O → (65-70% H₂SO₄) CH₃-CH(OH)-CH₃
(CH₃)₂C=CH₂ → (H₂O/H⁺) (CH₃)₃C-OH

2. Oxidation:
1. Combustion: CO₂ + H₂O
2. Hydroboration-oxidation: Alkenes react with diborane to form trialkyl boranes which on oxidation with alkaline H₂O₂ give alcohols.
3CH₂=CH₂ → (BH₃) (CH₃CH₂)₃B (Triethylborane) → (H₂O₂/OH^-) 3CH₃CH₂OH (Ethyl alcohol)
3. Oxymercuration-demercuration:
H₂C=CH₂ → (Hg(OAc)₂, THF, H₂O) OH-CH₂-CH₂-Hg OAc → (NaBH₄, OH^-) CH₃CH₂OH + Hg
4. Oxidation with potassium permanganate:
2KMnO₄ + H₂O → 2KOH + 2MnO₂ + 3[O]
3 >C=C< + H₂O + [O] (from KMnO₄, pink colour) → (Cold) 3 >C(OH)-C(OH)< (Colourless)
Bayer's Test
CH₃-CH=CH₂ → (i) Alk. KMnO₄, (ii) H⁺, Δ → CH₃COOH + CO₂ + H₂O
Oxidation with Ozone: Ozonolysis gives carbonyl compounds
CH₃CH₂CH=C(CH₃)₂ → (O₃) Ozonide → (Zn/H₂O) CH₃CH₂CHO + CH₃COCH₃ + Zn(OH)₂

Alkynes

Preparation:

From vicinal dihalides: dehalogenation
CH₃-CHBr-CH₂-Br → (2KOH (alc), Δ) CH₃-C≡CH + 2KBr + 2H₂O
By the action of water on calcium carbide:
CaC₂ + 2H₂O → HC≡CH + Ca(OH)₂

Reactions

(1) Addition Reaction: Alkyne show electrophilic addition reaction.
1. Addition of Hydrogen - Hydrogenation.
CH₃C≡CH (Propyne) + 2H₂ → (Ni) CH₃CH₂CH₃
Reduction of alkynes (Lindlar catalyst and Birch reduction)
CH₃C≡CCH₃ → (H₂/Lindlar Catalyst) cis-but-2-ene (the two CH₃ groups on the same side of the double bond)
CH₃C≡CCH₃ → (Na/NH₃ (liq.)) trans-but-2-ene (the two CH₃ groups on opposite sides of the double bond)
2. Addition of Halogens:
HC≡CH + 2Br₂ → Br₂HC-CHBr₂
3. Addition of hydrogen halides:
HC≡CH + 2HBr → CH₃CHBr₂
4. Addition of water (Hydration): Acid catalyzed addition of water
HC≡CH + H₂O → (HgSO₄, H₂SO₄) [CH₂=CHOH] (Unstable) → CH₃CHO
5. Polymerisation:
(a) Linear polymerization of ethyne gives polyacetylene or polyethyne which is a high molecular weight polyene containing repeating units of (CH=CH-CH=CH) and can be represented as -(CH=CH-CH=CH)n-
(b) Cyclic polymerization results in the formation of aromatic compound.
3 HC≡CH → (Red hot iron tube, 873 K) Benzene

Aromatic Hydrocarbon

Preparation of Benzene

(i) Decarboxylation of aromatic acids.
Sodium benzoate (C₆H₅COONa) + NaOH → (CaO, Δ) Benzene + Na₂CO₃
(ii) Reduction of phenol: Phenol is reduced to benzene by passing its vapours over heated zinc dust
Phenol + Zn → (Δ) Benzene + ZnO

Reactions of benzene

Nitration: Benzene → (Conc. HNO₃ + Conc. H₂SO₄) Nitrobenzene + H₂O
Halogenation: Benzene → (Anhyd. AlCl₃ + Cl₂) Chlorobenzene + HCl
Sulphonation: Benzene → (H₂SO₄ (SO₃)) Benzene sulphonic acid + H₂O
Friedel-Crafts alkylation: Benzene → (AlCl₃ + C₂H₅Cl) Ethyl benzene + HCl
Friedel-Crafts acylation: Benzene → (Anhyd. AlCl₃ + CH₃COCl) Acetophenone (C₆H₅COCH₃) + HCl
Benzene on treatment with excess of chlorine in the presence of anhydrous AlCl₃ in dark yields hexachlorobenzene (C₆Cl₆)
Benzene + 6Cl₂ → (Anhyd. AlCl₃, dark, cold) Hexachlorobenzene (C₆Cl₆) + 6HCl

Directive influence of a functional group in monosubstituted benzene:

1. Ortho and para directing groups and activating: -OH, -NH₂, -NHR, -NHCOCH₃, -OCH₃, -CH₃, -C₂H₅ etc.
2. Meta directing group and deactivating: -NO₂, -CN, -CHO, -COR, -COOH, -COOR, -SO₃H.
3. Ortho and para directing groups and deactivating - Halogens because of their strong -I effect, overall electron density on benzene ring decreases. However due to resonance the electron density on o- and p- position is greater than that at the m-position. Hence, they are also o- and p- directing groups.

21. POLYMERS

Important Addition Polymers

Polyolefins

1. Polythene

Polymer of ethylene or ethene.
(a) Low density polythene (LDP)
nCH₂=CH₂ (Ethene) → (350-750 K/1000 to 2000 atm, traces of O₂) (CH₂-CH₂)_n (Polythene)
(b) High density polythene (HDP)
nCH₂=CH₂ (Ethene) → (333-343 K/6-7 atm, Ziegler Natta catalyst) (CH₂-CH₂)_n (Polythene)
(d) Polyacrylonitrile
nCH₂=CHCN (Acrylonitrile) → (Polymerisation/Peroxide catalyst) (CH₂-CN-CN)_n (Polyacrylonitrile)
2. Polystyrene (Styrone)
n CH₂=CH-C₆H₅ (styrene) → (Benzoyl peroxide, (C₆H₅COO)₂) [-CH(C₆H₅)-CH₂-]_n
3. Polyvinylchloride (PVC)
n CH₂=CHCl (chloroethene, vinyl chloride) → (Dibenzoyl peroxide) [-CH₂-CHCl-]_n (PVC)
4. Polypropylene (PP)
n CH₃-CH=CH₂ (Propylene) → (Polymerisation) [-CH(CH₃)-CH₂-]_n (Polypropylene (PP))
5. Polytetrafluoroethene (Teflon)
nCF₂=CF₂ (Tetrafluoroethene) → (catalyst/High pressure) (CF₂-CF₂)_n (Teflon)
6. Polyacrylonitrile
n(CH₂=CHCN) (acrylonitrile) → (Polymerisation, Peroxide catalyst) [-CH₂-CH(CN)-]_n (Polyacrylonitrile or orlon)

Condensation polymers

Polyamides

(a) Nylon 6, 6: It is prepared by the condensation polymerization of hexamethylenediamine with adipic acid under high pressure and at high temperature.
nHOOC(CH₂)₄COOH + nH₂N(CH₂)₆NH₂ → (553 K/High pressure) [-NH-(CH₂)₆-NH-CO-(CH₂)₄-CO-]_n (Nylon 6,6)
(b) Nylon 6: It is obtained by heating caprolactum with water at a high temperature
Caprolactam → (533-543 K, H₂O) [-CO-(CH₂)₅-NH-]_n (Nylon 6)

Polyesters

(a) Terylene or Dacron: It is manufactured by heating a mixture of ethylene glycol and terephtalic acid at 420 to 460 K in the presence of zinc acetate-antimony trioxide catalyst.
nHOCH₂-CH₂OH (Ethylene glycol [Ethane-1, 2-diol]) + nHOOC-C₆H₄-COOH (Terephthalic acid [Benzene-1,4-dioic acid]) → [-OCH₂-CH₂-O-CO-C₆H₄-CO-]_n (Terylene or dacron)
2. Glyptal
nHO-CH₂-CH₂-OH (ethylene glycol) + n Phthalic acid (C₆H₄(COOH)₂) → (Heat, -nH₂O) [-O-CH₂-CH₂-O-CO-C₆H₄-CO-]_n (glyptal)

Polymethylmethacrylate (PMMA)

The polymer is known by several commercial names such as lucite, acrylite, plexiglass and perspex.

Resins

1. Phenol-Formaldehyde Polymer

These polymers are obtained by the condensation reaction of phenol with formaldehyde in the presence of either acid or a base catalyst. The reaction involves the formation of methylene bridge at ortho, para or both ortho and para positions. A linear or cross linked material is obtained depending upon the condition of reaction.
Phenol + CH₂O → (H⁺ or OH^-) o-hydroxymethylphenol + p-hydroxymethylphenol (with a second CH₂OH at the ortho position) + 2,4,6-tris(hydroxymethyl)phenol
n o-hydroxymethylphenol → (H⁺) Novolac (linear chain of phenol rings joined by -CH₂- bridges at ortho and para positions)
(b) Novolac on heating with formaldehyde forms Bakelite (rings of the Novolac chains joined by additional -CH₂- cross-links)

2. Urea-Formaldehyde Resin

NH₂-CO-NH₂ (urea) + 2HCHO (formaldehyde) → (Heat) HOCH₂-NH-CO-NH-CH₂OH → (Polymerisation) (-CH₂-NH-CO-NH-CH₂-)_n (urea-formaldehyde resin)

4. Melamine - formaldehyde polymer: Melamine formaldehyde polymer is formed by the condensation polymerization of melamine and formaldehyde
Melamine (triazine ring with three NH₂ groups) + HCHO → Resin intermediate (one NH₂ replaced by NHCH₂OH) → (Polymerisation) Melamine polymer (triazine rings joined through -NH-CH₂- links)

4. Natural Rubber

Natural rubber is a coiled linear 1, 4-polymer of isoprene.
Isoprene: CH₂=C(CH₃)-CH=CH₂
(a) Natural rubber: Natural rubber is a linear polymer of isoprene (2-methyl-1, 3-butadiene) and is also called as cis-1, 4-polyisoprene.

Vulcanisation of Rubber

The properties of natural rubber can be modified by introducing -S-S- polysulphide crosslinks in its structure.
The process of heating a mixture of raw rubber with sulphur and an appropriate additive in a temperature range between 373 K to 415 K to improve upon physical properties like elasticity, strength etc.
[Figure: Sulphur cross links in vulcanised rubber - polyisoprene chains joined by -S-S- or -S- bridges at the carbon next to the double bond]

Synthetic rubber

(A) Neoprene or polychloroprene
nCH₂=C(Cl)-CH=CH₂ (2-chloro-1,3-butadiene) → (Polymerisation) [CH₂-C(Cl)=CH-CH₂]_n (Neoprene)
(B) Buna - N
nCH₂=CH-CH=CH₂ (1,3-butadiene) + nCH₂=CH-CN (Acrylonitrile) → (Copolymerisation) [CH₂-CH=CH-CH₂-CH₂-CH(CN)]_n (Buna-N)
(C) Buna - S
nCH₂=CH-CH=CH₂ (1,3-butadiene) + nC₆H₅CH=CH₂ (Styrene) → [CH₂-CH=CH-CH₂-CH₂-CH(C₆H₅)]_n (Butadiene-styrene copolymer (Buna-S))

Biopolymers and Biodegradable Polymers

Aliphatic polyesters are the common examples of biodegradable Polymers.
(a) Poly-β-hydroxybutyrate-co-β-hydroxy valerate (PHBV):
It is obtained by the copolymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid
CH₃-CH(OH)-CH₂-COOH (3-Hydroxybutanoic acid) + CH₃CH₂-CH(OH)-CH₂-COOH (3-Hydroxypentanoic acid) → [-O-CH(CH₃)-CH₂-CO-O-CH(C₂H₅)-CH₂-CO-]_n (PHBV)
(b) Nylon 2-nylon 6: It is an alternating polyamide copolymer of glycine (H₂N-CH₂-COOH) and amino caproic acid (H₂N(CH₂)₅COOH)
nH₂N-CH₂-COOH (Glycine) + nH₂N-(CH₂)₅-COOH (Amino caproic acid) → (HN-CH₂-CO-HN-(CH₂)₅-CO)_n

Some polymers: