The label "2‑ethyl‑2,4,6‑trimethylheptane" was found on a bottle of liquid hydrocarbons. Although the name defines a structure unambiguously, it is not the correct IUPAC substitutive name. Give the correct name for the compound. Details count; pay attention to hyphens, commas, and spelling.

Start by drawing the structure of "2-ethyl-2,4,6-trimethylheptane." The sketch should show all the C-C bonds. However, for this question, it's not necessary to show any of the H atom in this molecule.

Draw the "backbone"

Consider the backbone of "2-ethyl-2,4,6-trimethylheptane." The backbone of a hydrocarbon is the trailing part of its name. ("-heptane" in this case.)

"hept-" means that there are seven carbon atoms in the backbone.
"-ane" (as opposed to -ene or -yne) means that all carbon-carbon bonds in this backbone are single bonds.

Hence, draw seven carbon atoms (preferably in a row or a column.) Connect each one with its two neighbors with a single dash (to represent a carbon-carbon single bond.)

Add the "substituents"

Number the seven carbon atoms from the previous step with number 1 through 7.

Now, look at prefixes of "2-ethyl-2,4,6-trimethylheptane." That's all the numbers, dashes, and letters before the name for the backbone. Substituents are grouped by types. In this case, there are two types of "substituents" in this "compound:"

"2-ethyl": one ethyl group ([tex]\text{-}\mathrm{CH_2}\text{-}\mathrm{CH_3}[/tex], two carbon atoms) at carbon number [tex]2[/tex].
"2,4,6-trimethyl": three methyl groups ([tex]\text{-}\mathrm{CH_3}[/tex], one carbon atom) at carbon number [tex]\text{2, 4, 6}[/tex] (one at each carbon backbone position.)

Refer to the first sketch attached.

Identify the real backbone using IUPAC rules

Refer to the IUPAC nomenclature for hydrocarbons (i.e., IUPAC's rules for naming hydrocarbons molecules.) The backbone shall be the longest path of carbon atoms in the molecule. In this case, the longest path contains eight carbon atoms (not seven, as "-heptane" suggests.) Refer to the second sketch. The real backbone is highlighted in light green.

The prefix for an eight-atom backbone is "oct-." Since there's only single bonds, the name of the backbone should be "octane."

Add the substituents

Carbon atoms that are not on the backbone are substituents. In this case, the substituents are all methyl groups [tex]\text{-}\mathrm{CH_3}[/tex], and there are four of them (highlighted in purple in the second sketch.) That corresponds to the prefix "tetra-." Hence the "tetramethyl-."

Number atoms in the backbone. Start from the end that would give the first of this substituent the smallest index number. In the sketch, the first substituent would be of index 3 if started from the lower-left side. However, the first substituent would be of index 2 if started from the right-hand side. Hence, start from the right-hand side.

The name and index of the substituents should be "2,2,4,6-tetramethyl."

Combining the parts

The name for the substituents should be joined to the name for the backbone without any space or hyphen in between. Hence the name for this compound: 2,2,4,6-tetramethylheptane.