Directions: This section contains multiple choice questions....

Directions: This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct.
The correct decreasing order of reactivity of the following alcohols towards con. HCl is

Key Concepts

Carbocation Stability

Carbocation stability is crucial in determining the rate of SN1 reactions. When an alcohol is protonated by HCl, it can form a carbocation if it is sufficiently stable. Tertiary carbocations are the most stable due to hyperconjugation and inductive effects, which increases the reactivity of the corresponding alcohol under acidic conditions.

Protonation and Leaving Group Formation

In the reaction of alcohols with hydrogen halides, the initial protonation of the hydroxyl group converts it into a better leaving group, water. This protonation step is essential as it facilitates the formation of either a carbocation intermediate (in SN1 reactions) or a suitable substrate for a backside attack (in SN2 reactions), thereby determining the overall reactivity of the alcohol.

Nucleophilic Substitution Mechanisms

This concept involves understanding how substitution reactions occur, particularly via SN1 and SN2 pathways. In reactions involving alcohols and hydrogen halides like HCl, the mechanism often depends on the stability of intermediates formed. Tertiary alcohols typically proceed through an SN1 pathway involving carbocation intermediate formation, while primary and some secondary alcohols tend to undergo SN2 reactions without carbocation formation.

Alcohol Structure and Reactivity

The structure of the alcohol, including whether it is primary, secondary, or tertiary, significantly influences its reactivity with HCl. Tertiary alcohols, due to their ability to form stable carbocations, are usually more reactive under conditions favoring SN1 reactions, while primary alcohols, which react via SN2 mechanisms, exhibit lower reactivity due to steric factors and the nature of the mechanism.

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