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

Answer 1

#"3,4,4,7-tetramethylnonane"#

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.

The last factors we need to think about are: counting from the left gives the correct carbon indexing because part of the IUPAC naming is to minimize the carbon indexing.

Okay, so...

Thus, we ought to obtain:

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

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Answer 2

Santiago Alfonso

The name "7-ethyl-3,4,4,7-tetramethylheptane" is not correct because the numbering of the parent chain should start from the end that gives the substituents the lowest possible numbers. It should be "2-ethyl-3,3,4,7-tetramethylheptane."

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Answer from HIX Tutor

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