GRE Subject Test: Chemistry : Nucleophilic Substitution

Study concepts, example questions & explanations for GRE Subject Test: Chemistry

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Example Questions

Example Question #1 : Mechanisms And Intermediates

When exposed to a good nucleophile, which molecule will most readily undergo an  reaction?

Possible Answers:

Correct answer:


 reactions, also known as unimolecular nucleophilic substitution reactions, occur in two steps. Here, we are concerned with the first and second (rate-determining) steps, in which the leaving group breaks off of the molecule to form a carbocation. Alkanes that form the most stable carbocations are most likely to undergo  reactions. Tertiary carbocations are the most stable, followed by secondary. Primary and methyl carbocations are very unstable and unlikely to form at all. The tertiary alkane, , will form a very stable tertiary carbocation compared to the other answer choices.

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