CBSE Class 12 Chemistry Concept Map All chapters

CBSE Class 12 Chemistry Concept Map All chapters. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

These Class 12 Chemistry concept maps bring the whole course onto a few pages: salt analysis of anions and cations, nitrogen compounds and diazonium chemistry, haloalkanes, alcohols, carboxylic acids, aldehydes and ketones, colloids, the oxygen family, d and f block elements, polymers, chemistry in everyday life and proteins. Use them for quick revision before the CBSE board exam.

ANION ANALYSIS

Salt + dil H₂SO₄ → Effervescence: could be CO₃^2-, SO₃^2-, S^2-, NO₂^-
Salt + dil H₂SO₄ → No effervescence: could be Cl^-, Br^-, I^-, NO₃^-, CH₃COO^-; then salt + conc H₂SO₄ + warm. If there is no effervescence, test using SCE (see next section).

Effervescence with dil H₂SO₄: smell the gas

1. Odourless gas, could be CO₃^2- → pass the gas through limewater → limewater turns milky: confirms CO₃^2-
2. Smell of burning hair, could be SO₃^2- → pass the gas through (1) acidified K₂Cr₂O₇ solution: turns green, confirms SO₃^2-; (2) acidified KMnO₄ solution: KMnO₄ is decolourised, confirms SO₃^2-
3. Smell of rotten egg, could be S^2- → pass the gas through acidified lead acetate solution → lead acetate solution turns black: confirms S^2-
4. Colourless gas turning brown, could be NO₂^-

No effervescence with dil H₂SO₄: salt + conc H₂SO₄ + warm, observe the colour of the gas

1. Colourless gas giving dense white fumes with ammonia, could be Cl^-. Confirmation: SCE + dil HNO₃ + AgNO₃ solution → white ppt soluble in NH₄OH confirms Cl^-. Also, salt + MnO₂ + conc H₂SO₄ + Δ → greenish yellow gas, could be Cl^-. Chromyl chloride test: salt + K₂Cr₂O₇ + conc H₂SO₄; pass the gas evolved through water, acidify the water with acetic acid and add lead nitrate. Reddish brown gas turns water yellow, finally a yellow ppt soluble in NaOH confirms Cl^-.
2. Reddish brown gas, could be Br^-. Confirmation: SCE + CHCl₃/CCl₄ + Cl₂ water → red/brown colour in the organic layer confirms Br^-.
3. Black/violet gas, could be iodide. Confirmation: SCE + CHCl₃/CCl₄ + Cl₂ water → violet colour in the organic layer confirms I^-.
4. Light brown gas turning dense brown on heating, could be NO₃^-. Confirmation: salt + Cu turnings + conc H₂SO₄ + heat → brown gas and the solution turns blue, could be NO₃^-. Brown ring test: SCE + FeSO₄ solution + dil H₂SO₄, then conc H₂SO₄ along the walls of the test tube → brown ring at the junction of the two layers confirms NO₃^-.

SALTS THAT DO NOT GIVE EFFERVESCENCE WITH dil H₂SO₄ / conc H₂SO₄

Preparation of SCE, i.e. sodium carbonate extract: salt + same quantity of Na₂CO₃ + water, boil and filter. The filtrate is called SCE.

ANALYSIS OF CATIONS

Original salt solution + dil HCl.

1. White ppt, could be Pb²⁺. Dissolve in hot water to get a colourless solution, could be Pb²⁺. Divide into two parts. Add K₂CrO₄: yellow ppt soluble in NaOH solution confirms Pb²⁺. Add KI: yellow ppt soluble in hot water, which reappears on cooling as golden yellow spangles, confirms Pb²⁺.
2. No ppt → pass H₂S. Black ppt, could be Pb²⁺/Cu²⁺. Dissolve in minimum quantity of 50% HNO₃; a colourless solution could be Pb²⁺ (tested as in 1), a blue solution could be Cu²⁺. Divide into three parts: add NH₄OH → deep blue colouration; add potassium ferrocyanide → chocolate brown ppt, confirms Cu²⁺; add KI → dirty white ppt.
3. No ppt with H₂S → boil off H₂S, add dil HNO₃ + NH₄Cl solution + NH₄OH. A ppt could be Fe³⁺, Al³⁺, Mn²⁺: gelatinous brown could be Fe³⁺; gelatinous white could be Al³⁺. Dissolve the ppt in minimum amount of HCl.
4. Fe³⁺: divide into two parts. Add potassium ferrocyanide solution → deep blue colour. Add potassium sulphocyanide solution → blood red colour. Fe³⁺ confirmed.
5. Al³⁺: add NaOH solution and a drop of litmus → blue lake floating in a colourless background confirms Al³⁺.
6. No ppt with NH₄OH → pass H₂S through the above solution. Black ppt could be Co²⁺ and Ni²⁺. Dissolve the ppt in minimum amount of aqua regia and evaporate to dryness. Blue residue could be Co²⁺; yellow residue could be Ni²⁺.
7. White ppt could be Zn²⁺. Dissolve in dil HCl and add NaOH solution: white ppt soluble in excess of NaOH confirms Zn²⁺.
8. No ppt → boil off H₂S, add Na₂CO₃ solution. White ppt could be Ca²⁺, Ba²⁺, Sr²⁺. Dissolve the ppt in minimum quantity of acetic acid and divide into three parts.
9. Add K₂CrO₄ solution: yellow ppt soluble in NaOH could be Ba²⁺; green colour on flame test confirms Ba²⁺.
10. Add ammonium acetate: no ppt. Add ammonium carbonate: white ppt could be Sr²⁺; red colour on flame test confirms Sr²⁺.
11. If there is no ppt with ammonium acetate or K₂CrO₄, add ammonium carbonate: white ppt could be Ca²⁺; brick red on flame test confirms Ca²⁺.
12. Individual tests are done for Na⁺, K⁺, Mg²⁺, NH₄⁺.

ORGANIC CHEMISTRY: COMPOUNDS CONTAINING NITROGEN

Amines

N is sp³ hybridised. Classified as 1°, 2° and 3° depending on the number of H atoms replaced by alkyl or aryl groups in NH₃.
Common name: alkyl amines. IUPAC names: alkane amines and aryl amines.

Physical properties

Lower aliphatic amines are soluble in water (H bonding). Solubility is inversely proportional to molecular mass. Aromatic amines are insoluble in water.
BP of amines: 1° > 2° > 3° amines. BP is proportional to intermolecular H bonding. Acids > Alcohols > Amines > Hydrocarbons.

Chemical properties

Basicity 2° > 3° > 1° (in aqueous phase). Ethanamine > NH₃ > Aniline. EDG → increase basicity. EWG → decrease basicity.
With alkyl halides: alkylation.
1° and 2° amines react with acid chlorides, acid anhydrides and esters by nucleophilic substitution.
Carbylamine reaction: 1° amines on heating with CHCl₃ and KOH form isocyanides with an obnoxious smell.
1° aliphatic amines + NaNO₂ + HCl → alcohol. 1° aromatic amines + NaNO₂ + HCl → diazonium salts.
1° and 2° amines + C₆H₅SO₂Cl (Hinsberg reagent) → sulphonamide.
Electrophilic substitution occurs at the o- and p- positions.
1° and 2° amines + RMgX → alkanes.

Cyanides

Common name: alkyl cyanides. IUPAC name: alkane nitriles.
Physical: lower members are liquids while higher members are solids. Solubility in water decreases as the number of C atoms increases. Soluble in organic solvents. Due to dipolar association BP is higher than hydrocarbons.

Chemical

Hydrolysis: RCN → RCOOH
RCN (LiAlH₄ or Na + C₂H₅OH) → RCH₂OH
RCN (SnCl₂/HCl + H₂O) → RCHO (Stephen's reaction)
RCN + NH₃ → R-C(=NH)-NH₂

Diazonium salts

IUPAC name: alkyl diazonium salt; aryl diazonium salt.
Physical: alkyl salts are more soluble than aryl salts. Readily soluble in water, but benzene diazonium fluoroborate is insoluble in water. Soluble in solution and decomposes in the dry state.

Chemical: displacement of N₂

ArN₂⁺X^- + CuCl/HCl → ArCl; CuBr/HBr → ArBr; CuCN/KCN → ArCN (Sandmeyer reaction)
Cu/HCl → ArCl; Cu/HBr → ArBr (Gattermann reaction)
KI → ArI
HBF₄/Δ → ArF (via ArN₂BF₄, then Δ)
H₂O/Δ → ArOH
H₃PO₂ + H₂O → ArH; CH₃CH₂OH → ArH
Diazo group is retained (coupling reactions): colourless diazonium salts form brightly coloured azo compounds Ar-N=N-Ar.

Nitrites

IUPAC name: alkyl nitrites. They contain the -O-N=O group and are isomeric to nitroalkanes.
R-O-N=O + Sn/HCl → ROH + NH₂OH
R-O-N=O + H₂O/H⁺ → ROH + HNO₂

Nitro compounds

IUPAC name: nitroalkanes.
Physical: colourless and pleasant smelling liquids. Less soluble in water but soluble in organic solvents. High boiling point. High dipole moment.

Chemical

Reduction: RNO₂ + Sn/HCl → R-NH₂; Zn/NH₄Cl → R-NH-OH
Hydrolysis: RCH₂NO₂ + H₂O (HCl) → R-COOH; 2R₂CHNO₂ (HCl) → 2R₂CO
Halogenation: RCH₂NO₂ + Br₂/NaOH → dibromo derivative; R₂CHNO₂ + Br₂/NaOH → monobromo derivative; R₃CNO₂ + Br₂/NaOH → no reaction

Isocyanides

Common name: alkyl isocyanides. IUPAC name: alkyl carbylamines.
Physical: highly poisonous and obnoxious smelling liquid. BP lower than cyanides. Insoluble in water.

Chemical

Hydrolysis: R-NC + H₃O⁺ → RNH₂ (primary amines)
Reduction: R-NC + LiAlH₄ → RNHCH₃ (secondary amines)
R-NC + HgO → R-NCO + Hg (alkyl isocyanate)
R-NC (Δ/250°C) → RCN (isomerisation)

BENZENEDIAZONIUM CHLORIDE

Diazotisation: C₆H₅NH₂ + HNO₂ (NaNO₂ + HCl) → C₆H₅N₂⁺Cl^- (benzenediazonium chloride) + NaCl + H₂O. Benzenediazonium chloride is stable due to resonance.

H₃PO₂/H₂O → benzene + N₂ + H₃PO₃ + HCl
CH₃CH₂OH → benzene + N₂ + CH₃CHO + HCl
CuCl/HCl → chlorobenzene + N₂
CuBr/HBr → bromobenzene + N₂
CuCN/KCN → benzonitrile + N₂
Cu/HCl → chlorobenzene + N₂ + CuCl
KI → iodobenzene + N₂ + KCl
HBF₄ → C₆H₅N₂⁺BF₄^-; Δ → fluorobenzene + N₂ + BF₃
H₂O → phenol + N₂ + HCl
HBF₄, then NaNO₂/Cu, Δ → nitrobenzene + N₂ + NaBF₄
Coupling with phenol (HO^-) → p-hydroxyazobenzene (orange dye)
Coupling with aniline → p-aminoazobenzene (yellow dye)

The diazonium ion, being a weak electrophile, can couple with a strongly activated aromatic system.
Coupling does not occur in strongly acidic medium: aniline is protonated to anilinium ion (less activated aromatic system).
In strongly alkaline medium, the concentration of the diazonium ion (which acts as the electrophile) decreases (diazonium ion is converted to the diazotate), and the coupling reaction does not occur.

[Figure: Reaction map of benzenediazonium chloride at the centre with all products listed above, drawn with benzene rings]

CHARACTERS OF AMINES

CONTROLLED BROMINATION AND NITRATION OF ANILINE

Controlled bromination: aniline + (CH₃CO)₂O (pyridine) → N-phenylethanamide (acetanilide) → Br₂/CH₃COOH → p-bromoacetanilide → OH^-/H⁺ → p-bromoaniline
Controlled nitration: aniline + (CH₃CO)₂O (pyridine) → acetanilide → HNO₃, H₂SO₄, 288 K → p-nitroacetanilide → OH^-/H⁺ → p-nitroaniline

CONVERSIONS

Aliphatic conversions: stepping up the series

R-OH (alcohol) → HX, anhydrous ZnCl₂ → R-X (alkyl halide) → alc. KCN → R-CN (nitrile) → LiAlH₄ (reduction) → R-CH₂NH₂ (primary amine)
R-CH₂NH₂ → HNO₂ (NaNO₂ and HCl) → R-CH₂OH (primary alcohol)
R-CN → hydrolysis, H₃O⁺ → RCOOH (carboxylic acid) → LiAlH₄, H₃O⁺ → R-CH₂OH (primary alcohol)
R-CH₂OH → oxidation → RCOOH
Hydrocarbon → X₂/UV → R-X (alkyl halide)

Aliphatic conversions: stepping down the series

RCOOH (carboxylic acid) → NH₃, Δ → RCONH₂ (acid amide) → Br₂/KOH → R-NH₂ (amine) → HNO₂ (NaNO₂ and HCl) → R-OH (primary alcohol) → HX, anhydrous ZnCl₂ → R-X (alkyl halide)
R-CH₂-X (alkyl halide) → aqueous KOH → R-CH₂-OH (primary alcohol) → alkaline KMnO₄ → RCOOH

Aromatic conversions: when the functional group contains carbon atom

Chlorobenzene → NaOH, 623 K, 300 atm, then H⁺ → phenol → Zn dust → benzene → CH₃Cl, anhydrous AlCl₃ → toluene → alkaline KMnO₄ → benzoic acid (HOOC-C₆H₅) → SOCl₂ → benzoyl chloride (ClOC-C₆H₅) → H₂/Pd, BaSO₄, S, boiling xylene → benzaldehyde (OHC-C₆H₅)

Aromatic conversions: when the functional group does not contain carbon atom

Benzene → conc. HNO₃, H₂SO₄, 333 K → nitrobenzene → Sn/HCl → aniline → NaNO₂/HCl → benzenediazonium chloride
Benzenediazonium chloride → warm H₂O → phenol → Zn dust → benzene
Benzenediazonium chloride → H₃PO₂/H₂O → benzene
Benzenediazonium chloride → KI → iodobenzene; CuCl/HCl → chlorobenzene; CuBr/HBr → bromobenzene
Benzenediazonium chloride → HBF₄ → benzenediazonium tetrafluoroborate → Δ → fluorobenzene; NaNO₂, Cu, Δ → nitrobenzene

CONCEPT MAP: COLLOIDS

Classification of colloids

Based on particles of dispersed phase: i) multimolecular, ii) macromolecular, iii) associated
Based on nature of interaction: i) lyophilic, ii) lyophobic
Based on physical state: i) solid in solid, ii) liquid in solid, iii) gas in solid, iv) solid in liquid, v) liquid in liquid, vi) gas in liquid, vii) solid in gas, viii) liquid in gas

Preparation of colloids

Chemical method
Bredig's arc method
Peptisation

Properties of colloids

Tyndall effect
Brownian motion
Electrophoresis
Colligative properties
Charge on colloidal particle
Colour
Coagulation

Purification

Dialysis
Electrodialysis
Ultrafiltration

CONCEPT MAP: CLASSIFICATION OF HALOALKANES (CHAPTER 10)

On the basis of the number of halogen atoms: monohalo derivative, dihalo derivative (CH₂X-CH₂X), trihalo derivative (CHX₃, haloforms)
On the basis of hybridisation of the carbon atom: compounds in which halogen is bonded to sp³ hybridised C (e.g. CH₃CH₂CH₂-X); allylic halides (e.g. CH₂=CH-CH₂-X); vinylic halides (CH₂=CH-X)
On the basis of 1°, 2° and 3° carbon atoms: primary haloalkane (CH₃-CH₂-X); secondary haloalkane (CH₃-CH(X)-CH₃); tertiary haloalkane ((CH₃)₃C-X)

[Figure: Flow chart of classification of haloalkanes; parts of two boxes at the left edge of the source page are cut off]

PREPARATION OF HALOALKANES

From alcohols: R-OH + HX (ZnCl₂) → RX + H₂O
From hydrocarbons: CH₃CH₂CH₂CH₃ + Cl₂ (UV) → CH₃CH₂CH₂CH₂Cl + CH₃CH₂CH(Cl)CH₃
From alkenes: CH₂=CH₂ + HX → CH₃CH₂-X
By halide exchange: Finkelstein reaction: RX + NaI → RI + NaX (X = Cl, Br). Swarts reaction: RX + AgF → RF + AgX

Nucleophilic substitution of haloalkanes

R-X + KOH (aq.) → R-OH + KX
R-X + NaOR → R-O-R + NaX
R-X + KCN (alc) → R-CN + KX
R-X + AgCN → R-NC + AgX
R-X + KNO₂ → R-O-N=O

UNIT 11: ALCOHOLS, PHENOLS AND ETHERS: CHEMICAL PROPERTIES OF ALCOHOLS

Reactions involving the cleavage of O-H bond: with metals, 2ROH + 2Na → 2RONa + H₂; esterification, RCOOH + R'OH → RCOOR' + H₂O
Reactions involving the cleavage of C-O bond: with HX, ROH + HX → RX + H₂O; with PCl₅, ROH + PCl₅ → RCl + POCl₃ + HCl
Reactions involving the alkyl group as well as the OH group: dehydration, oxidation and dehydrogenation

Dehydration (order of ease 3° > 2° > 1°): CH₃CH₂OH + H₂SO₄, 443 K → CH₂=CH₂ + H₂O
Oxidation: CH₃CH₂OH + K₂Cr₂O₇ + H₂SO₄ → CH₃CHO; further [O] → CH₃COOH
Dehydrogenation: RCH₂OH (573 K, Cu) → RCHO + H₂

UNIT 12: TEST FOR CARBOXYLIC ACIDS

Classification of carboxylic acids

CHEMICAL PROPERTIES OF ALDEHYDES AND KETONES

Nucleophilic addition reactions: 1. by HCN, 2. by NaHSO₃, 3. by RMgX, 4. by NH₃
Reduction
Oxidation

OXYGEN FAMILY

General electronic configuration: ns² np⁴. Members: 1. Oxygen (O), 2. Sulphur (S), 3. Selenium (Se), 4. Tellurium (Te), 5. Polonium (Po)
Anomalous behaviour: points of difference of the first member of the group with other group members: exceptionally small atomic and ionic size; absence of d-orbitals in the valence shell; high ionisation energy and high electronegativity.
O₂ molecule is paramagnetic due to the presence of two unpaired electrons in anti-bonding M.O.
Ozone, O₃, is a powerful oxidizing agent, because it can give nascent oxygen [O].
It is also called the chalcogen family because most copper minerals contain either oxygen or sulphur.
Oxygen shows -2 oxidation state except OF₂ (+2), O₂F₂ (+1) and peroxides (-1).
Hydrides of the oxygen family: H₂O, H₂S, H₂Se, H₂Te

CONCEPT MAP: d AND f BLOCK ELEMENTS

d-block elements

Physical properties: 1. variation in M.P.; 2. variation in atomic and ionic size; 3. ionisation enthalpies; 4. oxidation state variation; 5. trends in standard electrode potentials; 6. trends in stability of higher oxidation states.
Special properties: 1. variable oxidation states; 2. coloured ions; 3. catalytic properties; 4. complex formation; 5. alloy formation; 6. interstitial compounds; 7. paramagnetism.
Some important compounds: KMnO₄ (preparation, structure and its properties); K₂Cr₂O₇ (preparation, structure and its properties).

f-block elements

POLYMERS IN ONE PAGE

Classification as elastomer, fibre, thermoplastic and thermosetting polymer

CHEMISTRY IN EVERYDAY LIFE IN ONE PAGE

Therapeutic action of different drugs. Note: all the medicines should be taken under strict medical supervision.

Chemicals in food

Cleansing agents

Detergents with highly branched hydrocarbon parts are non-biodegradable and hence water pollutants, so branching is minimised, which makes them degradable and prevents pollution.

CONCEPT MAP: BIOMOLECULES (PROTEINS)

Proteins are all the polymers of α-amino acids connected to each other by peptide bond or peptide linkage.
Classification based on molecular structure: 1. Fibrous: insoluble in water, polypeptide chains run parallel, held by H bonds and disulphide bonds. Ex: keratin. 2. Globular: chains of polypeptides coil around to give a spherical shape. Ex: insulin.
Structure: Primary: sequence of amino acids. Secondary: shape due to H-bonding. Tertiary: overall folding of the secondary structure. Quaternary: special arrangement of subunits with respect to each other.
Essential amino acids: which cannot be made in the body, to be supplied through diet. Non-essential: can be synthesised by the body.
α-Helix: formed due to intramolecular H-bonds between the C=O of one amino acid residue and the N-H of the 4th amino acid residue in the chain. Ex: keratin in hair and myosin in muscles.
β-Pleated structure: peptide chains laid side by side, held together by intermolecular H-bonding, resembles pleated folds of drapery. Ex: silk protein.
Denaturation: due to coagulation the native shape of the protein is destroyed and biological activity is lost; 2° and 3° structures are destroyed, 1° is intact.