What is the structure of 2-ethyl-3-hexyne?

1 Answer
Jan 2, 2017

Answer:

Are you sure this is an hexyne, and not an heptyne?

Explanation:

#"3-hexyne"# #-=# #H_3C-CH_2C-=C-CH_2CH_3#,

Because this is an even-numbered acetylene, we could number from either end. The third and fourth carbon along the chain are triply bound.

Given this structure, we have defined the numbering system. #C2# is an ethyl group.........

#"2-ethyl-3-hexyne"# #-=# #H_3C-CH(CH_2CH_3)C-=C-CH_2CH_3#,

but this is not a valid name, because the longest chain is now 7 carbons long. Organic nomenclature insists that first you find the LONGEST hydrocarbyl chain. This is therefore an heptyne derivative.

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