carboxylic acid because they are less oxidized groups.6 . A
This molecule is 3-ethyl-4-methylhexane, not 2,3-diethylpentane. When naming alkanes, one
must locate the longest carbon chain (6 carbons, rather than 5 carbons), and the numbering
system should give the alkyl groups the lowest possible numbers.7 . B
We know from the IUPAC name that we have a butanedioic acid backbone—in other words, a
four-carbon backbone with carboxylic acids at either end. Adding the hydroxyl groups at carbons
2 and 3 then yields the correct structure.8 . B
Form– is a prefix shared by the common names of methanoic acid (formic acid) and methanal
(formaldehyde).9 . A
The first task in naming a compound is identifying the longest carbon chain. In this case, the
longest chain has seven carbons, so the parent alkane ends in –heptane. Choices (B) and (D) can
therefore be eliminated. Then, we must make sure that the carbons are numbered so that the
substituents’ position numbers are as small as possible. This compound has two methyl groups;
minimizing their position numbers requires us to number the chain from right to left. These
methyl groups are attached to carbons 2 and 5, so the correct IUPAC name is 2,5-
dimethylheptane. Choice (C) is incorrect because the position numbers of the substituents are
not minimized.10 . D
We begin by finding the longest carbon chain; because there are no non-alkyl groups, we don’t
need to worry about any other groups’ priorities. We then number our carbons such that the
lowest possible combination of numbers is given to the various substituents. Then substituents
are organized alphabetically, not numerically—eliminating choice (C).
11 . B
We know right away that choices (C) and (D) will be incorrect because a hydroxyl group is of
higher priority than a methyl group. We also know that we will number the carbon chain so that
the hydroxyl group receives the lowest possible position. Therefore, this molecule is 2-methyl-2-