Question

Why is this name not correct? `"7-ethyl-3,4,4,7-tetramethylheptane"`; what should it be?

Answer 1

`"3,4,4,7-tetramethylnonane"`

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The longest chain is `9` carbons, not `7`. So the parent name should be a nonane.

• Counting from the left, we then land on a methyl (`-"CH"_3`) group on carbon-3, two methyl groups on carbon-4, and one methyl group on carbon-7.

• Counting from the right, we then land on a methyl (`-"CH"_3`) group on carbon-3, two methyl groups on carbon-6, and one methyl group on carbon-7.

Part of the IUPAC naming is to minimize the carbon indexing, so counting from the left gives the correct carbon indexing. The last things we need to consider are

• how to denote duplicates
• how to denote how many duplicates of methyl groups we have.

Well...

• They are all methyl groups, so we don't have to worry about alphabetical ordering. We then list the carbon indices that the methyl groups are connected to.
• The prefix for four duplicate groups is "tetra".

So we should then get:

`color(blue)ul"3,4,4,7-tetramethylnonane"`