CBSE Class 12 Chemistry Alcohols Phenol And Ethers Worksheet Set 01

Question 1. Give IUPAC names and structures of:- (a) Isobutyl alcohol (b) Sec - butyl alcohol (c) tert-butyl alcohol (d) n-amyl alcohol (e) o-cresol (f) Catechol (g) glycerol (h) picric acid (i) vinyl alcohol (j) benzyl ale (k) Aspirin (l) cyclohexyl methanol
Answer:
(a) Isobutyl alcohol - IUPAC name: 2-Methylpropan-1-ol, Structure: \((CH_3)_2CH-CH_2-OH\)
(b) Sec-butyl alcohol - IUPAC name: Butan-2-ol, Structure: \(CH_3-CH(OH)-CH_2-CH_3\)
(c) tert-butyl alcohol - IUPAC name: 2-Methylpropan-2-ol, Structure: \((CH_3)_3C-OH\)
(d) n-amyl alcohol - IUPAC name: Pentan-1-ol, Structure: \(CH_3-CH_2-CH_2-CH_2-CH_2-OH\)
(e) o-cresol - IUPAC name: 2-Methylphenol, Structure: \(2-(CH_3)C_6H_4-OH\)
(f) Catechol - IUPAC name: Benzene-1,2-diol, Structure: \(C_6H_4(OH)_2\)
(g) glycerol - IUPAC name: Propane-1,2,3-triol, Structure: \(CH_2(OH)-CH(OH)-CH_2(OH)\)
(h) picric acid - IUPAC name: 2,4,6-Trinitrophenol, Structure: \((NO_2)_3C_6H_2-OH\)
(i) vinyl alcohol - IUPAC name: Ethenol, Structure: \(CH_2=CH-OH\)
(j) benzyl alcohol - IUPAC name: Phenylmethanol, Structure: \(C_6H_5-CH_2-OH\)
(k) Aspirin - IUPAC name: 2-Acetyloxybenzoic acid, Structure: \(C_6H_4(OCOCH_3)COOH\)
(l) cyclohexyl methanol - IUPAC name: Cyclohexylmethanol, Structure: \(C_6H_{11}-CH_2-OH\)
In simple words: IUPAC names are derived by identifying the longest carbon chain containing the hydroxyl group and numbering it to give the OH group the lowest possible locant.
Exam Tip: Always number the carbon chain starting from the end closest to the principal functional group (-OH).

Question 2. Give reasons for the following:-
(i) Commercially carboxylic acids are not reduced to alcohols directly instead alcohols are obtained by converting them to ester followed by their reduction.
(ii) Alcohols and phenols are Bronsted acids.
(iii) Alcohols are weaker acids than water.
(iv) In esterification reaction between carboxylic and alcohol, water is removed as soon as it is formed.
(v) Esterification reaction between acid chloride and alcohol is carried out in presence of pyridine.
(vi) 3, 3-Dimethyl butan-2-ol on acid catalyzed dehydration yields an unexpected 2,3-dimethyl but 2-ene as major product.
(vii) n-hexanol is not soluble in water.
(viii) Unlike most phenols, 2, 4-dinitrophenol & 2, 4, 6-trinitrophenol is soluble in aqueous sodium bicarbonate solution.
(ix) Phenol has a smaller dipole moment (\(1.54\text{ D}\)) than methanol (\(1.71\text{ D}\)).
(x) For the prepn of alkyl halides from alcohols, thionyl chloride is preferred over other reagents.
(xi) Phenols do not give protonation reactions easily.
Answer:
(i) Direct reduction of carboxylic acids requires expensive reducing agents like \(LiAlH_4\), whereas esters can be easily and economically reduced using hydrogen in the presence of a catalyst.
(ii) Alcohols and phenols can donate a proton to form alkoxide and phenoxide ions respectively, acting as Bronsted acids.
(iii) The alkoxide ion is less stable than the hydroxide ion due to the electron-donating inductive effect of the alkyl group, making alcohols weaker acids than water.
(iv) Esterification is a reversible reaction; removing water shifts the equilibrium to the right in accordance with Le Chatelier's principle to maximize the yield of the ester.
(v) Pyridine neutralizes the \(HCl\) formed during the reaction, preventing the reverse reaction and driving the equilibrium forward.
(vi) The initially formed secondary carbocation undergoes a 1,2-methyl shift to form a more stable tertiary carbocation, which upon loss of a proton yields 2,3-dimethylbut-2-ene as the major product.
(vii) The large non-polar hydrocarbon chain of n-hexanol overwhelms the hydrogen-bonding capability of the hydroxyl group, making it insoluble in water.
(viii) The strong electron-withdrawing nitro groups in 2,4-dinitrophenol and 2,4,6-trinitrophenol increase their acidity sufficiently to react with weak bases like sodium bicarbonate, releasing carbon dioxide.
(ix) In phenol, the resonance effect pulls electron density away from the oxygen atom into the benzene ring, opposing the inductive effect and reducing the dipole moment compared to methanol where only the inductive effect operates.
(x) Thionyl chloride is preferred because the by-products formed are gases (\(SO_2\) and \(HCl\)), which escape leaving behind pure alkyl halide.
(xi) The lone pair of electrons on the oxygen atom of phenol is delocalized into the benzene ring through resonance, imparting partial double bond character to the \(C-O\) bond and making protonation difficult.
In simple words: These reasons are based on fundamental principles of electronic effects, chemical equilibria, stability of intermediates, and reaction mechanisms.

Exam Tip: For acid strength questions, always explain using the stability of the conjugate base formed.

Question 3. Carry out the following conversions in 2 steps-
(a) Propane to propan-1-ol
(b) Benzyl chloride to benzyl alcohols
(c) Ethyl magnesium chloride to propan-1-ol.
(d) Methyl magnesium bromide to 2-methyl propan-2-ol.
(e) Phenol to picric acid.
(f) Benzene to phenol
(g) Isopropyl alcohol to acetone
(h) Methanol to ethane
(i) Propyne to 2-propanol
(j) Acetylene to ethanol
(k) Isopropyl alcohol to n-propyl bromide
(l) Propyne to 1-bromopropane
Answer:
(a) Propane to propan-1-ol: Step 1: \(CH_3CH_2CH_3 \xrightarrow{Cl_2/\text{UV light}} CH_3CH_2CH_2Cl\)
Step 2: \(CH_3CH_2CH_2Cl \xrightarrow{aq. KOH} CH_3CH_2CH_2OH\)
(b) Benzyl chloride to benzyl alcohol: Step 1: Hydrolysis with aqueous alkali or sodium carbonate.
\(C_6H_5CH_2Cl \xrightarrow{NaOH (aq)} C_6H_5CH_2OH + NaCl\)
(c) Ethyl magnesium chloride to propan-1-ol: Step 1: Reaction with formaldehyde to form an addition complex.
\(CH_3CH_2MgCl + HCHO \rightarrow CH_3CH_2CH_2OMgCl\)
Step 2: Hydrolysis.
\(CH_3CH_2CH_2OMgCl + H_2O \xrightarrow{H^+} CH_3CH_2CH_2OH + Mg(OH)Cl\)
(d) Methyl magnesium bromide to 2-methylpropan-2-ol: Step 1: Reaction with acetone.
\(CH_3MgBr + CH_3COCH_3 \rightarrow (CH_3)_3COMgBr\)
Step 2: Acid hydrolysis.
\((CH_3)_3COMgBr + H_2O \xrightarrow{H^+} (CH_3)_3COH + Mg(OH)Br\)
(e) Phenol to picric acid: Step 1: Sulfonation of phenol with conc. \(H_2SO_4\).
Step 2: Nitration with conc. \(HNO_3\).
(f) Benzene to phenol: Step 1: Chlorination of benzene to chlorobenzene.
Step 2: Dow's process (\(NaOH, 623\text{ K}, 300\text{ atm}\) followed by acidification).
(g) Isopropyl alcohol to acetone: Step 1: Catalytic dehydrogenation over copper at \(573\text{ K}\).
\((CH_3)_2CHOH \xrightarrow{Cu, 573 K} (CH_3)_2CO + H_2\)
(h) Methanol to ethane: Step 1: Convert methanol to methyl iodide. Step 2: Wurtz reaction with sodium metal.
(i) Propyne to 2-propanol: Step 1: Hydration in presence of \(Hg^{2+} / H_2SO_4\) to form acetone.
Step 2: Reduction with \(NaBH_4\) or \(LiAlH_4\).
(j) Acetylene to ethanol: Step 1: Hydration of acetylene to acetaldehyde. Step 2: Reduction of acetaldehyde to ethanol.
(k) Isopropyl alcohol to n-propyl bromide: Step 1: Dehydration of isopropyl alcohol to propene using conc. \(H_2SO_4\).
Step 2: Anti-Markovnikov addition of \(HBr\) in the presence of peroxide to give 1-bromopropane.
(l) Propyne to 1-bromopropane: Step 1: Partial catalytic hydrogenation or hydroboration-oxidation to propanal. Step 2: Reduction or hydrohalogenation steps appropriately.
In simple words: These multi-step conversions link different functional groups using standard organic reactions like substitution, addition, oxidation, and reduction.

Exam Tip: Always write reaction conditions (catalysts, temperature, reagents) explicitly above the reaction arrows.

Q1. Give IUPAC names and structures of:-

(a) Isobutyl alcohol                 (b) Sec – butyl alcohol

(c) tert-butyl alcohol               (d) n-amyl alcohol

(e) o-cresol                            (f) Catechol

(g) glycerol                            (h) picric acid

(i) vinyl alcohol                       (j) benzyl ale

(k) Aspirin                             (l) cyclobexyl methanol

Q2. Give reasons for the following:-

(i) Commercially carboxylic acids are not reduced to alcohols directly instead alcohols are obtained by converting them to ester followed by their reduction.

(ii) Alcohols and phenols are Bronsted acids.

(iii) Alcohols are weaker acids than water.

(iv) In esterification reaction between carboxylic and alcohol, water is removed as soon as it’s formed.

(v) Esterification reaction between acid chloride and alcohol is carried out in presence of pyridine.

(vi) 3, 3-Dimethyl butan-2-ol on acid catalyzed dehydration yields an unexpected 2,3-dimethyl but 2-ene as major product.

(vii) n-hexanol is not soluble in water

(viii) Unlike most phenols, 2, 4-dinitrophenol & 2, 4, 6–trinitraphenol is soluble in aqueous sodium bicarbonate solution.

(ix) Phenol has a smaller dipole moment (1.54, 0) than methanol (1.71 D)

(x) For the prepn of alkyl halides from alcohols, through chloride is preferred over other reagents.

(xi) Phenols do not give protonation reactions easily.

MCQ Questions for NCERT CBSE Class 12 Chemistry Alcohols Phenole And Ethers

Question.   

(a) Benzaldehyde
(b) Benzoic acid
(c) Benzene
(d) Toluene

Answer: B

Question.  

(a) Etard reaction
(b) Gattermann Koch reaction
(c) Williamson synthesis
(d) Esterification

Answer: C

Question. The heating of phenyl methyl ether with HI produces
(a) Iodobenzene
(b) Phenol
(c) Benzene
(d) Ethyl chloride

Answer: B

Question. How many alcohols with molecular formula C4H10O are chiral in nature?
(a) 1
(b) 2
(c) 3
(d) 4

Answer: A

Question. What is the correct order of reactivity of alcohols in the following reaction?
R—OH + HCl znCl₂ → R—Cl + H₂O
(a) 1° > 2° > 3°
(b) 1° < 2° > 3°
(c) 3° > 2° > 1°
(d) 3° > 1° > 2°

Answer: C

Question. CH₃CH₂OH can be converted into CH₃CHO by ________________.
(a) catalytic hydrogenation
(b) treatment with LiAlH4
(c) treatment with pyridinium chlorochromate
(d) treatment with KMnO₄

Answer: C

Question. Among the following sets of reactants which one produces anisole?
(a) CH₃CHO; RMgX
(b) C₆H₅OH; NaOH, CH₃I
(c) C₆H₅OH, neutral FeCl₃
(d) C₆H₅—CH₃; CH₃COCl; AlCl₃

Answer: B

Question. Which of the following gives positive iodoform test?
(a) C₆H₅CH₂CH₂OH
(b) CH₃CH(CH₃)CH₂OH
(c) PhCHOHCH₃
(d) CH₃CH₂CH(OH) CH₂CH₃

Answer: C

Question. Monochlorination of toluene in sunlight followed by hydrolysis with aq. NaOH yields.
(a) o-Cresol
(b) m-Cresol
(c) 2, 4-Dihydroxytoluene
(d) Benzyl alcohol

Answer: A

Question. Which of the following are used to convert RCHO into RCH₂OH? 
(a) H₂/Pd
(b) LiAlH4
(c) NaBH4
(d) Reaction with RMgX followed by hydrolysis

Answer: A , B , C

Question. Arrange the following in decreasing order of acidic character:   

(a) IV > III > I > II
(b) II > IV > I > III
(c) I > II > III > IV
(d) III > I > II > IV

Answer: D

Question. Arrange the following compounds in increasing order of boiling point. Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol
(a) Propan-1-ol, butan-2-ol, butan-1-ol, pentan-1-ol
(b) Propan-1-ol, butan-1-ol, butan-2-ol, pentan-1-ol
(c) Pentan-1-ol, butan-2-ol, butan-1-ol, propan-1-ol
(d) Pentan-1-ol, butan-1-ol, butan-2-ol, propan-1-ol

Answer: A

Question. Write the IUPAC name of the given compound:  

(a) 2,3- dinitrophenol
(b) 2,5- dinitrophenol
(c) 2,4- dinitrophenol
(d) 2,5- nitrophenol

Answer: B

Question. Which of the following compound would not react with Lucas reagent at room temperature?
(a) CH₂ = CH—CH₂OH
(b) C6H5CH₂OH
(c) CH₃CH₂CH₂OH
(d) (CH₃)₃ COH

Answer: D

Question. Which of the following compounds will react with sodium hydroxide solution in water?
(a) C₆H₅OH
(b) C₆H₅CH₂OH
(c) (CH₃)₃ COH
(d) C₂H₅OH

Answer: A

Question. IUPAC name of the compound is _______________ .    

(a) 1-methoxy-1-methylethane
(b) 2-methoxy-2-methylethane
(c) 2-methoxypropane
(d) isopropylmethyl ether

Answer: C

Assertion Reason Based Question :

In the following question a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct and reason is correct explanation of assertion.
(b) Assertion and reason both are wrong statements.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(e) Both assertion and reason are correct statements but reason is not correct explanation of assertion.

Question. Assertion: Like bromination of benzene, bromination of phenol is also carried out in the presence of Lewis acid.
Reason: Lewis acid polarises the bromine molecule.

Answer: D

(a) Assertion and reason both are correct and reason is correct explanation of assertion.
(b) Assertion and reason both are wrong statements.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(e) Both assertion and reason are correct statements but reason is not correct explanation of assertion.

Question. Assertion: Bond angle in ethers is slightly less than the tetrahedral angle.
Reason: There is a repulsion between the two bulky (—R) groups.

Answer: D

Question. When salicylic acid is heated with Zn dust , what will be the main product ?
a) Benzene
b) phenol
c) Toluene
d) Benzoic acid
Answer. D

Question. To prepare butan-2-ol using CH₃MgI, what other chemical would you choose ?
a) Propanal
b) Ethanal
c) Ethanol
d) Propan-2-ol
Answer. A

Question. Which of the following cannot be made by using Williamson’s synthesis ?
a) Methoxy benzene
b) tert-butyl ethyl ether
c) allyl methyl ether
d) Ditert-butyl ether
Answer. D

Question. Heating of phenyl methyl ether with HI produces
a) Iodobenzene
b) phenol
c) benzene
c) ethyl chloride
Answer. B

ASSERTION REASON TYPE QUESTIONS
For questions given below two statements are given- one labelled Assertion (A) and the other labelled as Reason (R). Select the correct answer from the codes (A) , (B) , ( C) and (D) as given below :
(A) Bothe assertion and reason are correct statements , and reason is the correct explanation of the assertion.
(B) Both assertion and reason are correct statements , but reason is not the correct explanation of the assertion
(C) Assertion is correct , but reason is wrong statement
(D) Assertion is wrong , but reason is correct statement

Question. Assertion (A) : The carbon-oxygen bond length in phenol is slightly less than that in methanol.
Reason (R) : The carbon –oxygen bond in phenol has partial double bond character due to + R effect
Answer. A

Question. Assertion (A) : Aldehydes are reduced to primary alcohols by using LiAlH₄
Reason (R) : LiAlH₄ is a strong reducing agent
Answer. A

Question. Assertion (A) : The acid strength of primary alcohol is more than secondary alcohol
Reason (R) : + I effect decreases the acid character
Answer. A

Question. Assertion (A) : o- nitrophenol has lower boiling point than p-nitrophenol
Reason (R) : o-nitrophenol possess intramolecular hydrogen bonding while p-nitrophenolhas intermolecular hydrogen bonding
Answer. A

Question. Assertion (A) : t-Butyl methyl ether on treatment with HI at 373K gives a mixture of methyliodide and tert-butyl alcohol
Reason (R) : The reaction occurs by S_N¹ mechanism
Answer. D

SHORT ANSWER TYPE QUESTIONS

Question. Arrange the following compounds in increasing order of their acid strength: Propan-1-ol, 2, 4, 6-trinitrophenol, 3-nitrophenol, 3, 5-dinitrophenol, phenol, 4-methylphenol.
Answer. Propan-1-ol, 4-methylphenol, phenol, 3-nitrophenol, 3, 5-dinitrophenol, 2, 4, 6-trinitrophenol.

Question. How primary, secondary and tertiary alcohols are distinguished by Lucas reagent test? Alcohols react with hydrogen halides to form alkyl halides.
Answer. The difference in reactivity of three classes of alcohols with HCl distinguishes them from one another (Lucas test). Alcohols are soluble in Lucas reagent (conc. HCl and ZnCl₂) while their halides are immiscible and produce turbidity in solution. In case of tertiary alcohols, turbidity is produced immediately as they form the halides easily. Primary alcohols do not produce turbidity at room temperature.

Question. Ortho nitrophenol has lower boiling point than p-nitrophenol. Why?
Answer.  Ortho-nitrophenol has lower boiling point due to formation of intramolecular H-bonding whereas p-nitrophenol forms intermolecular H-bonding.

Question. The C-O bond is much shorter in phenol than in ethanol. Give reason.
Answer. Carbon of C-O bond of phenol is Sp² hybridised, so it acquires a partial double bond character but in ethanol it is Sp³ hybridised and a single bond. Double bond is shorter than a single bond.

Question. Give reasons for the following :
(i) Phenol is more acidic than methanol.
(ii) The C—O—H bond angle in alcohols is slightly less than the tetrahedral angle (190°28′).
(iii) (CH₃)₃C—O—CH₃ on reaction with HI gives (CH₃)₃C—I and CH₃—OH as the main products and not (CH₃)₃C—OH and CH₃—I.
Answer. (i) Phenol is more acidic than methanol because in phenol, phenoxide ion formed is more stabilized by resonance than phenol. There is no resonance in methanol.
(ii) The C—O—H bond angle in alcohols is slightly less than tetrahedral angle due to repulsion between the lone pairs of electrons of oxygen.
(iii) (CH₃)₃C⁺ is 3° carbo-cation which is more stable than CH₃⁺ for S_N¹ reaction.

2 Account for the following: 
i) C – O – H bond angle in alcohol is less than tetrahedral angle.
ii) C – O bond length in phenol is shorter than that in methanol.
iii) C – O – C bond angle in ether is greater than the tetrahedral angle.
iv) The boiling points of alcohols and phenols are higher than corresponding alkanes of same molecular mass.
v) Among the isomeric alcohols the boiling point follows the order 3⁰< 2⁰< 1⁰.
vi) Lower alcohols are soluble in water
vii) Ethanol is less acidic than methanol.
viii) The acidic character of the alcohols follows the order 1⁰> 2⁰> 3⁰
ix) The reaction of alcohol with acid is carried out in presence of small amount of concentrated H2SO4.
x) Reaction of alcohol with acid chloride is carried out in presence of a base pyridine.

3. Effect the following conversions: 
i) Chloro benzene to phenol                 vi) Propene to 1-Propanol
ii) Benzene sulphonic acid to phenol    vii) Propene to 2-propanol
iii) Ethanol to isopropyl alcohol            viii) Phenol to anisole
iv) Phenol to picric acid                       ix) Phenol to aspirin
v) Phenol to p-hydroxy acetophenone   x) Aniline to phenol

4. Arrange the following on the increasing property given in bracket: 
a) Pentan-1-ol, butan-1-ol, butan-2-ol, ethanol, propan-1-ol, methanol (Boiling Point)
b) Pentan-1-ol, n-butane, pentanal, Ethoxyethane (Boiling point)
c) Propan-1-ol, 2, 4, 6 – trinitro phenol, 3,5 – dinitro phenol, 4-methylphenol (Acidity)
d) Ter. Butyl alcohol, isobutyl alcohol, n-butyl alcohol (Acidity)
e) 4-nitro phenol, phenol, 2,4,6-trinitro phenol (Acid strength )

5. Write short note on the following: 
i) Hydroboration
iv) Kolbe’s reaction
ii) Reimer – Tiemann Reaction.
v) Williamson’s synthesis
iii) Friedel-Craft’s reaction

THREE MARK QUESTION
1. Write the mechanism of the following: Acid catalyzed dehydration of ethanol to diethyl ether.

VALUE BASED QUESTION
1. Leanne, a student of class XII is working in her chemistry laboratory. She is checking the action of acid chlorides and acid anhydrides on phenols. She found that as a result of one reaction aspirin is formed as product. She kept aspirin for medical use.
a) Write the reaction for the formation of aspirin.
b) What do you mean by acetylation reaction?
c) Why is pyridine added in the reaction of alcohols with acid chloride
d) Why Leanne is storing aspirin for medical use? Is her this act correct? Give reason.