CBSE Class 12 Chemistry Alcohols Phenols and Ethers Worksheet Set A

Question. Alcohols have higher boiling point than parent hydrocarbons because of
(a) higher molecular mass
(b) presence of hydrogen bonding
(c) presence of carbon chain
(d) None of the above
Answer. B

Question. Which enzyme converts glucose and fructose both into ethanol?
(a) Maltase
(b) Diastase
(c) Invertase
(d) Zymase
Answer. D

Question. The reagent which easily reacts with ethanol and propanol is
(a) Grignard reagent
(b) Fehling reagent
(c) aqua-regia
(d) Tollen’s reagent
Answer. A

Question. 1-propanal and 2-propanal can differentiated by
(a) oxidation with acidic K₂ Cr₂ O₇ followed by reaction with Fehling solution
(b) oxidation with KMnO₄ followed by reaction with Fehling solution
(c) oxidation with conc. H₂SO₄ followed by reaction with Fehling solution
(d) oxidation by heating with copper followed by reaction with Fehling solution
Answer. D

Question. A compound that easily undergoes bromination is
(a) benzene
(b) toluene
(c) phenol
(d) benzoic acid
Answer. C

Question. The reagent used for dehydration of an alcohol is
(a) phosphorus pentachloride
(b) aluminium oxide
(c) calcium chloride
(d) sodium chloride
Answer. B

Question. Complete the analogy regarding type of reaction.
Williamson ether synthesis : A : Aryl ether : B
(a) A : Nucleophilic substitution, B : Electrophilic substitution
(b) A : Electrophilic substitution, B : Electrophilic substitution
(c) A : Nucleophilic addition, B : Nucleophilic substitution
(d) A : Electrophilic substitution, B : Nucleophilic addition
Answer. B

Very Short Answer

Question. Who reported hydroboration first?
Answer. Hydroboration oxidation was first reported by H.C. Brown.

Question. What are the basic compounds for the formation of detergents, antiseptics and fragrances?
Answer. Alcohols, phenols and ethers are the basic compounds for the formation of the detergents, antiseptics and fragrances.

Question. Define acetylation?
Answer. The introduction of acetyl group in alcohols or phenols is known as acetylation.

Question. What is benzoquinone?
Answer. Oxidation of phenol with chromic acid produces a conjugated diketone known as benzoquinone.

Question. Define denaturation of alcohol?
Answer. The commercial alcohol is made unfit for drinking by mixing in it some copper sulphate and pyridine is called denaturation of alcohol.

Short Answer

Question. What do you understand by the Reimer-Tiemann reaction?
Answer. The Reimer-Tiemann reaction is an organic reaction used to convert a phenol to ohydroxyl benzalde-hyde using chloroform, a base, and acid work-up. The mechanism begins with abstraction of the proton from chloroform with the base to form a trichloro carbanion which spontaneously loses a chloride ion to form a neutral dichlorocarbene.
The base also deprotonates the phenol reagent which then attacks the carbene. A series of steps and a final acid work-up result in the o-hydroxyl benzaldehyde product

Question. What do you mean by Williamson synthesis?
Answer. The Williamson ether synthesis is an organic reaction, forming an ether from an organohalide and a deprotonated alcohol (alkoxide). This reaction was developed by Alexander Williamson. Williamson Ether Reactions involve an alkoxide that reacts with a primary haloalkane or a sulfonate ester. Alkoxides consist of the conjugate base of an alcohol and are comprised of an R group bonded to an oxygen atom. They are often written as RO–, where R is the organic substituent.

Question. What do you mean by the term esterification?
Answer. Esterification is the process of combining an organic acid (RCOOH) with an alcohol (ROH) to form an ester (RCOOR) and water; or a chemical reaction resulting in the formation of at least one ester product. Ester is obtained by an esterification reaction of an alcohol and a carboxylic acid.

Question. What do you understand by the Kolbe’s reaction?
Answer. The Kolbe reaction can be classified as a carboxylation chemical reaction. The reaction occurs when sodium phenoxide is allowed to absorb carbon dioxide and the resulting product is heated at a temperature of a 125-degree celsius and a pressure of over a hundred atmospheres.

Question. What do you mean by Friedel-crafts reaction?
Answer. A Friedel-Crafts reaction is an organic coupling reaction involving an electrophilic aromatic substitution that is used for the attachment of substituents to aromatic rings. An alkyl group can be added to a benzene molecule by an electrophile aromatic substitution reaction, for example: the addition of a methyl group to a benzene ring. The mechanism
for this reaction begins with the generation of a methyl carbocation from methyl bromide.

Long Answer

Question. Explain the preparation of phenols?
Answer. Phenols are prepared in the laboratory form benzene derivatives by any of the following methods:
1. Phenols from haloarenes can be obtaining chlorobenzene by the mono substitution of a benzene ring. When chlorobenzene fuses with sodium hydroxide at 623K and 320 atm, we obtain sodium phenoxide and finally sodium phenoxide on acidification gives phenols.
2. Phenols from benzenesulphonic acid can obtain Benzenesulphonic from benzene by reacting it with oleum. Benzenesulphonic acid, thus formed, is treated with molten sodium hydroxide at high temperature. This process leads to the formation of sodium phenoxide and finally, sodium phenoxide on acidification gives phenols.
3. Phenol from cumene can obtain by the Friedel-Crafts alkylation of benzene with propylene. Upon oxidation of cumene (isopropyl benzene) in presence of air, we obtain cumene hydro peroxide. Treatment of cumene hydro peroxide with dilute acid, we get the phenols. We also produce acetone as one of the by-products of this reaction in large quantities. Hence, phenols prepared by these methods need purifications.
4. Phenols from diazonium salts treat an aromatic primary amine with nitrous (NaNO₂ + HCl) acid at 273 – 278 K, we can easily obtain diazonium salts. These diazonium salts are highly reactive in nature. Upon warming with water, these diazonium salts finally hydrolyse to phenols. We can also obtain phenols from diazonium salts by treating it with dilute acids.

Question.State the difference between salicylic acid and acetylsalicylic acid?
Answer. 
1. Salicylic acid is a medication that we can use for the removal of the outer layer of our skin whereas acetylsalicylic is a medication that we use to treat pain, fever and inflammation.
2. Salicylic acid molar mass is 138.12 g/mol whereas acetylsalicylic acid molar mass is 180.15 g/mol.
3. Salicylic acid melting point is 158.6˚ C whereas acetylsalicylic acid melting point is 136˚ C.
4. Salicylic acid used as a food additive, food preservative, antiseptic, to treat dandruff, warts etc., whereas acetylsalicylic used only in medicinal.
5. In salicylic acid boiling point sublimation at 76˚ C and decomposition is at 200˚ C whereas in acetylsalicylic acid boiling point decomposition is at 140˚ C.

Question. State the difference between ethanol and methanol?
Answer. 
1. Ethanol is the alcohol with an ethyl group in the carbon skeleton whereas methanol is the alcohol with a methyl group in the carbon skeleton.
2. Ethanol is the alcohol found in beverages whereas methanol is highly toxic and not suitable for consumption.
3. Ethanol is produced by the fermentation of sugars by yeast whereas methanol is mostly produced synthetically through catalysis from carbon monoxide, carbon dioxide and hydrogen.
4. Ethanol is a weaker acid than water whereas methanol has a level of acidity slightly higher than that of water.
5. Ethanol can cause drowsiness which gets naturally balanced off by the natural bodily mechanisms whereas an amount less than half a teaspoon of a methanol is able to cause blindness.

Question. State the difference between primary alcohol and secondary alcohol?
Answer. 
1. Primary alcohol is an alcohol which has the hydroxyl group connected to a primary carbon atom whereas secondary alcohol is an alcohol which has the hydroxyl group on a secondary carbon atom.
2. Primary alcohols are difficult to dehydrate than secondary alcohols whereas secondary alcohols are easier to dehydrate.
3. Primary alcohols do not form oily layers whereas secondary alcohols form oily layers within about five minutes.
4. Primary alcohols are more acidic than secondary alcohols whereas secondary alcohols are less acidic.
5. Primary alcohols are less stable than secondary alcohols whereas secondary alcohols are more stable.
6. Primary alcohols give a blood red colour whereas secondary alcohols give a blue colour.

Question. State the difference between alcohols and phenols?
Answer. 
1. Alcohol is an organic compound whose molecule contains one or more hydroxyl groups attached to a carbon atom whereas phenol is a compound consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group.
2. Alcohols are used in the alcoholic beverage industry, pharmaceutical, ink and many more industries whereas phenols are mainly used as antiseptic agents.
3. Alcohols are a group of compounds whereas phenol is a specific compound.
4. Alcohols are generally aliphatic hydrocarbons whereas phenols are aromatic hydrocarbons.
5. Aliphatic alcohols are less acidic than phenol whereas phenols are acidic and should always be diluted before use.

Please click on below link to download CBSE Class 12 Chemistry Alcohols Phenols and Ethers Worksheet Set A