JEE Chemistry Alcohols Phenols and Ethers MCQs Set 13

Answer: (a) An ester

Explanation:
1. It is glyceryl trinitrate, the nitrate ester of glycerol.

Teacher's Note:
1. Glycerol is propane-1,2,3-triol; it gives nitroglycerine, allyl iodide with HI, and acrolein on dehydration.
2. Classify an alcohol by the carbon bearing OH: primary (CH2OH), secondary (CHOH) or tertiary (C-OH).

Answer: (a) Thio-alcohols

Explanation:
1. Mercaptans are thiols, R-SH.

Teacher's Note:
1. Learn the common names: carbinol, glycerol, catechol, pyrogallol, cresol, carbolic acid, picric acid.
2. Count the OH groups to decide whether an alcohol is mono-, di- or trihydric.

Answer: (c) Both the above

Explanation:
1. Both the catalytic hydration of ethene and fermentation of molasses are used industrially.

Teacher's Note:
1. Fermentation uses enzymes: diastase (starch to maltose), maltase (to glucose) and zymase (to ethanol and CO2).
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (c) Absorbing in \( \ce{H2SO4} \) followed by hydrolysis

Explanation:
1. Ethene is absorbed in conc.
2. \( \ce{H2SO4} \) to give ethyl hydrogen sulphate, which is hydrolysed to ethanol.

Teacher's Note:
1. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (c) Ethylene oxide

Explanation:
1. Grignard reagents open ethylene oxide to give a primary alcohol with two more carbons: \( \ce{CH3CH2CH2OH} \).

Teacher's Note:
1. Grignard reagents add to carbonyl groups and are destroyed by water, alcohols and acids.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (d) Enzymes

Explanation:
1. Diastase, maltase and zymase are the enzymes involved.

Teacher's Note:
1. Fermentation uses enzymes: diastase (starch to maltose), maltase (to glucose) and zymase (to ethanol and CO2).
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (c) Glycerol

Explanation:
1. Saponification of the triglyceride gives soap and glycerol.

Teacher's Note:
1. Glycerol is propane-1,2,3-triol; it gives nitroglycerine, allyl iodide with HI, and acrolein on dehydration.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (c) Zymase

Explanation:
1. Zymase from yeast ferments \( \ce{C6H12O6} \) to ethanol and \( \ce{CO2} \).

Teacher's Note:
1. Fermentation uses enzymes: diastase (starch to maltose), maltase (to glucose) and zymase (to ethanol and CO2).
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (a) Diastase, maltase and zymase

Explanation:
1. Starch is converted to maltose (diastase), maltose to glucose (maltase), and glucose to ethanol (zymase).

Teacher's Note:
1. Fermentation uses enzymes: diastase (starch to maltose), maltase (to glucose) and zymase (to ethanol and CO2).
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (b) HCHO

Explanation:
1. HCHO gives a primary alcohol with one more carbon; other aldehydes give secondary alcohols.

Teacher's Note:
1. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (c) Phenol

Explanation:
1. The diazonium group is replaced by OH: \( \ce{C6H5N2Cl + H2O -> C6H5OH + N2 + HCl} \).

Teacher's Note:
1. Diazonium salts give phenol on warming with water and azo dyes by coupling with phenols and amines.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (c) Ethyl alcohol

Explanation:
1. Carboxylic acids are reduced all the way to primary alcohols.

Teacher's Note:
1. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (b) Cannizzaro's reaction

Explanation:
1. Benzaldehyde has no alpha hydrogen, so with conc.
2. NaOH it gives benzyl alcohol and sodium benzoate.

Teacher's Note:
1. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (d) Phenol

Explanation:
1. Hydrolysis of the diazonium salt gives phenol.

Teacher's Note:
1. Diazonium salts give phenol on warming with water and azo dyes by coupling with phenols and amines.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (c) Williamson's synthesis

Explanation:
1. Alkoxide plus alkyl halide gives an ether: Williamson synthesis.

Teacher's Note:
1. Williamson synthesis is an SN2 reaction of an alkoxide with a primary alkyl halide; tertiary halides eliminate.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (b) Phenol, chloroform and sodium hydroxide

Explanation:
1. Reimer-Tiemann reaction.

Teacher's Note:
1. Reimer-Tiemann reaction formylates phenol at the ortho position through dichlorocarbene; with CCl4 it gives salicylic acid.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (d) An alcohol

Explanation:
1. Only compounds with an acidic hydrogen (OH of alcohols) liberate hydrogen with sodium.

Teacher's Note:
1. Acidity order: carboxylic acids > carbonic acid > phenol > water > alcohols; nitro groups increase and alkyl groups decrease the acidity of phenols.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (a) \( \ce{CH3CH(OH)CH3} \)

Explanation:
1. The tertiary alcohol comes from acetone and CH3MgI; acetone arises by oxidation of propan-2-ol.

Teacher's Note:
1. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.

Answer: (c) \( \ce{CH3OH} \)

Explanation:
1. \( \ce{CO + 2H2 -> CH3OH} \) (synthesis of methanol).

Teacher's Note:
1. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (b) \( \ce{CH3CH2OH} \)

Explanation:
1. Hydroboration followed by oxidation gives ethanol.

Teacher's Note:
1. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (c) Glucose + glucose

Explanation:
1. Maltose is a disaccharide of two glucose units.

Teacher's Note:
1. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (c) Distilling with the appropriate amount of benzene

Explanation:
1. A ternary azeotrope with benzene distils first, taking the water out; the remaining alcohol is anhydrous.

Teacher's Note:
1. Ethanol and water form an azeotrope with 95.6 percent alcohol; absolute alcohol needs benzene (azeotropic distillation) or quicklime and further drying.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (d) All of these

Explanation:
1. The nucleophilic carbon of RMgX adds to C=O, C#N and C=S.

Teacher's Note:
1. Grignard reagents add to carbonyl groups and are destroyed by water, alcohols and acids.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (a) Saponification

Explanation:
1. Alkaline hydrolysis of fats and oils is saponification.

Teacher's Note:
1. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (b) \( \ce{C2H5CH2CH2OH} \)

Explanation:
1. The Grignard carbon attacks the ring carbon: \( \ce{C2H5CH2CH2OMgBr} \), then hydrolysis gives butan-1-ol.

Teacher's Note:
1. Grignard reagents add to carbonyl groups and are destroyed by water, alcohols and acids.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (a) Phenol

Explanation:
1. Alkali fusion of sodium benzenesulphonate gives sodium phenoxide, which on acidification gives phenol.

Teacher's Note:
1. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.
2. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.

Answer: (b) Benzene diazonium chloride

Explanation:
1. Diazonium salts are hydrolysed by hot water to phenols.

Teacher's Note:
1. Williamson synthesis is an SN2 reaction: keep the bulky group on the alkoxide and use a primary alkyl halide.
2. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.

Answer: (b) \( \ce{C3H7OH} \)

Explanation:
1. \( \ce{C2H5MgI + HCHO} \) gives propan-1-ol after hydrolysis.

Teacher's Note:
1. Grignard reagent with HCHO gives primary, with other aldehydes secondary, with ketones and esters tertiary alcohols.
2. Remember the industrial routes: hydration of ethene, fermentation of sugars, water gas to methanol, cumene process for phenol.