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MCAT Organic Chemistry Question — Alcohol Reactions

Considering all “-R” groups to be alkyl groups, which alcohol is most reactive in an SN1 reaction with HCl?

a) primary alcohol

b) secondary alcohol

c) tertiary alcohol

d) number of substituent groups does not affect alcohol reactivity




Only tertiary alcohols form a carbocation stable enough for an SN1 mechanism. Primary and secondary alcohols react too slowly by SN1 mechanisms to for significant amounts of product in comparison with tertiary alcohols.

a) primary alcohol, incorrect, Primary alcohols do not form stable carbocations necessary for the SN1 mechanism with HCl.

b) secondary alcohol, incorrect, Same reason as choice a).

c) tertiary alcohol, correct.

d) number of substituent groups does not affect alcohol reactivity, incorrect, Substituent groups strongly affect alcohol reactivity, and primary and secondary alcohols do not react significantly with HCl by an SN1 mechanism.


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