ketone; and choice (C), a carboxylic acid, cannot form additional bonds to oxygen because they
have four bonds to other carbon or oxygen atoms already.12 . B
In this reaction, there has been an inversion of stereochemistry. The mostly likely explanation for
this is that the reaction proceeded by an SN2 reaction mechanism. Inversion of stereochemistry is
a hallmark of SN2 reactions, whereas racemization is a hallmark of SN1 reactions.
13 . D
To carry out a nucleophile–electrophile reaction, the nucleophile must be able to dissolve in the
solvent. Nucleophiles are nearly always polar, and often carry a charge. Polar solvents are
therefore preferred for these reactions. Hexane is a nonpolar solvent and will not be useful for a
nucleophile–electrophile reaction.
14 . A
Aldehydes have one alkyl group connected to the carbonyl carbon, whereas ketones have two.
This creates more steric hindrance in ketones, which lowers their reactivity to nucleophiles.
Ketones are also less reactive because their carbonyl carbon has less positive charge character;
the additional alkyl group can donate electron density—the opposite of choice (D)—which
decreases the electrophilicity of the compound.
15 . D
Remember, there is a hierarchy to the reactivity of carboxylic acid derivatives that dictates how
reactive they are toward nucleophilic attack. In order from highest to lowest, this is anhydrides >
carboxylic acids and esters > amides. In practical terms, this means that derivatives of higher
reactivity can form derivatives of lower reactivity but not vice-versa. Nucleophilic attack of an
ester cannot result in the corresponding anhydride because anhydrides are more reactive than
esters.