Answers and Explanations

DISCRETE PRACTICE QUESTIONS

1 . A

The common  name    of  ethanal is  acetaldehyde,   the common  name    of  methanal    is  formaldehyde,

and the common  name    of  ethanol is  ethyl   alcohol.    Isopropyl   alcohol is  the common  name    of  2-

propanol.   Propionaldehyde is  the common  name    of  propanal.

2 . C
Aldehydes and carboxylic acids are characterized by their positions at the ends of carbon
backbones and are thus considered terminal groups. As a result, the carbons to which they are
attached are usually designated carbon 1. Ketones are internal by definition because there must
be a carbon on either side of the carbonyl.

3 . C
The highest-priority functional group in this molecule is the carboxylic acid, so this will be a
component of the backbone and provides the suffix of the molecule. This molecule is 2-methyl-3-
oxopropanoic acid.

4 . A
This molecule features an anhydride. The only other groups are hydrocarbon chains, which will
provide part of the name of the parent root. Keep in mind that when a carbonyl group is present
with a leaving group, the larger functional group (carboxylic acid, anhydride, ester, amide) takes
priority over the carbonyl group alone. This molecule is propanoic anhydride.

5 . C
Among the functional groups presented, carboxylic acids have the highest priority, and their
compounds end with an –oic acid suffix. Choice (A) denotes an alcohol, choice (B) a ketone, and
choice (D) an alkyne, all of which have lower priorities than carboxylic acids. The MCAT does not
test nomenclature of halides or ethers, but note that these must have lower priority than a