The Strecker synthesis creates an amino acid from an aldehyde. The carbonyl carbon ultimately
becomes the α-carbon of the amino acid. Any remaining alkyl chain becomes the R group, as
shown below. The starting compound is therefore 2-methylpropanal (isobutyraldehyde).7 . D
One resonance structure of a C–N bond in an amide has the double bond between the C and N,
not between the C and O. Thus, the C–N bond of an amide has some sp^2 character, and sp^2 -
hybridized atoms exhibit planar geometry.8 . D
Both the Strecker and Gabriel syntheses contain planar intermediates, which can be attacked
from either side by a nucleophile. This results in a racemic mixture of enantiomers, and the
solution will therefore be optically inactive.9 . A
During the Gabriel synthesis, phthalimide attacks a secondary carbon in diethyl bromomalonate.
The secondary carbon is the electrophile, choice (D), and bromide is the leaving group, choice
(C).10 . C
The Gabriel synthesis includes two nucleophilic substitution steps, followed by hydrolysis and
decarboxylation. Dehydration—the loss of a water molecule—is not a part of this reaction.
11 . B
The pKa 2 of phosphoric acid is close to physiological pH; therefore, at
this pH.12 . C
Pyrophosphate is unstable in aqueous solution and will degrade to form two equivalents of
inorganic phosphate. The solvent is water, which should retain its polarity regardless of the