JEE Chemistry Alcohols Phenols and Ethers MCQs Set 19

Answer: (c) Only ethyl alcohol and acetone

Explanation:
1. Ethanol (oxidised to ethanal) and acetone have a \( \ce{CH3CO-} \) group; methanol does not.

Teacher's Note:
1. The iodoform test is positive for ethanol, CH3CH(OH)R and CH3CO-; methanol and primary alcohols other than ethanol do not respond.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (a) 2,4,6-Trinitrotoluene

Explanation:
1. TNT is trinitrotoluene with the nitro groups ortho and para to the methyl group (2,4,6-).

Teacher's Note:
1. Nitro groups at ortho and para positions increase the acidity of phenol, and ortho-nitrophenol is steam volatile.
2. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.

Answer: (c) More than water

Explanation:
1. Methanol is more volatile than water, so the solution has a vapour pressure above that of pure water.

Teacher's Note:
1. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (c) Glycerol trinitrate

Explanation:
1. Nitroglycerine is produced by esterification of all three OH groups.

Teacher's Note:
1. Glycerol is propane-1,2,3-triol; it gives nitroglycerine, allyl iodide with HI, and acrolein on dehydration.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (c) Functional isomers

Explanation:
1. Both are \( \ce{C2H6O} \) but have ether and alcohol groups.

Teacher's Note:
1. Ethers are cleaved by HI, form explosive peroxides in air, and act as Lewis bases forming etherates.
2. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.

Answer: (c) Azeotropic distillation

Explanation:
1. Benzene is added to give a ternary azeotrope that carries off the water.

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. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.

Answer: (b) Ethyl acetate and water

Explanation:
1. Esterification gives ethyl acetate and water.

Teacher's Note:
1. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (d) A bright yellow solid

Explanation:
1. 2,4,6-Trinitrophenol is a yellow crystalline solid.

Teacher's Note:
1. Nitro groups at ortho and para positions increase the acidity of phenol, and ortho-nitrophenol is steam volatile.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (b) Hydrogen bonding

Explanation:
1. Hydrogen bonds form between the OH groups and water.

Teacher's Note:
1. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (c) Dioxan

Explanation:
1. Intermolecular dehydration of two glycol molecules gives 1,4-dioxane.

Teacher's Note:
1. Dehydration of alcohols follows carbocation stability, so tertiary alcohols dehydrate fastest; ethanol gives ether at 413 K and ethene at 443 K.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (b) \( \ce{(CH3)3C-OH} \)

Explanation:
1. The tertiary carbocation is the most stable.

Teacher's Note:
1. Dehydration of alcohols follows carbocation stability, so tertiary alcohols dehydrate fastest; ethanol gives ether at 413 K and ethene at 443 K.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (d) O-H

Explanation:
1. O-H bond breaks to release H+ (to the metal), giving the ethoxide ion.

Teacher's Note:
1. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.
2. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.

Answer: (c) tert-Butyl alcohol

Explanation:
1. Branching decreases the hydrophobic surface; the tertiary isomer is the most soluble.

Teacher's Note:
1. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (b) \( \ce{CH3CH2CH2OH} \)

Explanation:
1. Only alcohols with the \( \ce{CH3CH(OH)-} \) group (and ethanol) respond.
2. Propan-1-ol does not.

Teacher's Note:
1. The iodoform test is positive for ethanol, CH3CH(OH)R and CH3CO-; methanol and primary alcohols other than ethanol do not respond.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (b) Emission of heat and contraction in volume

Explanation:
1. Strong ethanol-water hydrogen bonding releases heat and the mixture is slightly smaller in volume than the sum of the parts.

Teacher's Note:
1. Hydrogen bonding raises boiling point and solubility, while intramolecular bonding (o-nitrophenol) lowers boiling point.
2. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.

Answer: (b) Hydride shift

Explanation:
1. A 1,2-hydride shift moves H with its bonding pair to the neighbouring carbocation centre.

Teacher's Note:
1. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (a) Alkanes

Explanation:
1. \( \ce{ROH + R'MgX -> R'H + Mg(OR)X} \); the acidic OH proton gives an alkane.

Teacher's Note:
1. Grignard reagents add to carbonyl groups and are destroyed by water, alcohols and acids.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (c) \( \ce{N2} \)

Explanation:
1. \( \ce{C6H5OH + CH2N2 -> C6H5OCH3 + N2} \).

Teacher's Note:
1. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.
2. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.

Answer: (c) Imparts no effect

Explanation:
1. Isotopic substitution of ring hydrogen does not change the electron distribution at the OH group in any appreciable way.

Teacher's Note:
1. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (b) Alcohol

Explanation:
1. \( \ce{RCOOH + R'OH -> RCOOR' + H2O} \).

Teacher's Note:
1. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (b) Decolourising bromine in \( \ce{CCl4} \)

Explanation:
1. An alkene decolourises bromine in \( \ce{CCl4} \); an alcohol does not (both dissolve in cold conc. sulphuric acid and are oxidised by permanganate).

Teacher's Note:
1. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.
2. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.

Answer: (b) Liquid

Explanation:
1. Ethylene glycol is a viscous colourless liquid (b.p. 470 K).

Teacher's Note:
1. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (c) \( \ce{CCl3CHO} \)

Explanation:
1. Ethanol is oxidised by chlorine to ethanal which is then exhaustively chlorinated to chloral.

Teacher's Note:
1. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (d) Benzyl alcohol

Explanation:
1. Benzyl alcohol, \( \ce{C6H5CH2OH} \), has neither \( \ce{CH3CO-} \) nor \( \ce{CH3CH(OH)-} \).

Teacher's Note:
1. The iodoform test is positive for ethanol, CH3CH(OH)R and CH3CO-; methanol and primary alcohols other than ethanol do not respond.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (b) 3

Explanation:
1. The ethers of \( \ce{C4H10O} \) are methyl n-propyl ether, methyl isopropyl ether and diethyl ether: three metamers.

Teacher's Note:
1. Ethers are cleaved by HI, form explosive peroxides in air, and act as Lewis bases forming etherates.
2. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.

Answer: (a) Peroxide

Explanation:
1. Auto-oxidation gives ether hydroperoxides and peroxides.

Teacher's Note:
1. Ethers are cleaved by HI, form explosive peroxides in air, and act as Lewis bases forming etherates.
2. Hydrogen bonding explains most physical trends: boiling point, solubility and volatility of ethers, ortho-nitrophenol.

Answer: (c) \( \ce{C2H5OC2H5} \)

Explanation:
1. Diethyl ether boils at 308 K; the smaller ethers are gases at room temperature.

Teacher's Note:
1. Ethers are cleaved by HI, form explosive peroxides in air, and act as Lewis bases forming etherates.
2. Learn the identification tests: Lucas, iodoform, FeCl3, Victor Meyer, Liebermann, bromine water.

Answer: (a) Ethane

Explanation:
1. Reductive cleavage of both C-O bonds gives 2 ethane.

Teacher's Note:
1. Dehydration and substitution with HX both go through carbocations, so 3 degree > 2 degree > 1 degree.
2. Compare acidity through the stability of the conjugate base: electron-withdrawing groups strengthen the acid, electron-donating groups weaken it.