Alcohols, Aldehydes, Ketones and Carboxylic Acids MCQs for MDCAT

Correct answer: B. CH₃─CO─CH₂─CH₃

CH3-CO-CH2-CH3 (butanone) contains a carbonyl group flanked by two carbon-containing groups, making it a ketone.

Correct answer: B. Diethyl ether

Dehydration of ethanol with concentrated H2SO4 at 140°C (lower temperature, intermolecular reaction) gives diethyl ether, while higher temperatures (170°C) favour ethene formation.

Correct answer: B. Lactic acid

Lactic acid is not typically used as a denaturant for ethanol, unlike methanol, pyridine and acetone, which are commonly added to make alcohol unfit for drinking.

Correct answer: D. Ketones

Oxidation of a secondary alcohol yields a ketone, since the carbon bearing the hydroxyl group has only one hydrogen available for removal during oxidation.

Correct answer: B. Propane-1,2,3-triol

Fats (triglycerides) are esters formed between long-chain carboxylic (fatty) acids and glycerol, chemically named propane-1,2,3-triol.

Correct answer: D. LiAIH4

Lithium aluminum hydride (LiAlH4) is a strong reducing agent that is capable of reducing a wide range of functional groups, including carbonyl compounds (aldehydes, ketones, carboxylic acids), esters, amides, and others, to their corresponding alcohols. Therefore, option D is correct.

Correct answer: B. Secondary alcohol

Oxidation of alcohols convert them into aldehydes and ketones. The best reagent for this purpose is acid dichromate. Primary alcohols yield aldehydes whereas secondary alcohols yield ketones. Tertiary alcohols are resistant to oxidation.

Correct answer: B. 2,4-Dimethylpentan-3-one

2,4-Dimethylpentan-3-oneExplanation:Diisopropyl ketone refers to a ketone with two isopropyl groups attached to the carbonyl carbon.The correct structure has two methyl groups at positions 2 and 4 on a pentane chain, with the carbonyl group at position 3, hence the name 2,4-dimethylpentan-3-one.

Correct answer: D. Ethanol

The iodoform reaction occurs with compounds that have a methyl group attached to a carbon bearing a hydroxyl group (-OH) or a carbonyl group (-C=O). Ethanol (CH₃CH₂OH) meets this requirement because it can be oxidized to acetaldehyde (CH₃CHO), which has the necessary structure for the iodoform reaction.

Correct answer: B. Ethene

When ethyl alcohol reacts with H2SO4 at high temperature, beta elimination takes place resulting in formation of ethene.

Correct answer: A. Primary > Secondary >Tertiary.

This sequence is due to the following factors:Inductive Effects: In primary alcohols, there are fewer alkyl groups attached to the carbon bearing the hydroxyl group (-OH). Fewer alkyl groups mean less electron-donating inductive effect, which stabilizes the alkoxide ion by making it less negative. In contrast, tertiary alcohols have more alkyl groups, which destabilize the alkoxide ion by donating electron density, thus making tertiary alcohols less acidic.Steric Effects: Tertiary alcohols are more sterically hindered, which makes it more difficult for solvent molecules to stabilize the alkoxide ion through hydrogen bonding. This steric hindrance also lowers the acidity.

Correct answer: B. 2-propanol

The correct IUPAC name for isopropyl alcohol is propan-2-ol. This name reflects the structure of the molecule: a three-carbon chain (propane) with a hydroxyl group (-OH) attached to the second carbon atom. The prefix 'iso-' in isopropyl indicates the branching at the second carbon, which aligns with the IUPAC naming as 'propan-2-ol'.Option A (1-butanol) and Option D (2-butanol) are incorrect because they describe four-carbon alcohols, not three. Option C (1-propanol) is incorrect because the hydroxyl group is on the first carbon, not the second. Option E (propanol) is too vague as it doesn't specify the position of the hydroxyl group.