What is the IUPAC name for the following?

#color(white)(mmmmmmml)"CH"_2#
#color(white)(mmmmmmmll)"||"#
#"CH"_3"-CH"("CH"_3)"-C-CH"_2"-CH"_3#

The reason I fail to complete this is that I do not know how to write a IUPAC name for a double bond that is a chain.

1 Answer
May 7, 2018

The preferred IUPAC name is 2-methyl-3-methylidenepentane.

Explanation:

The latest (2013) version of the IUPAC Blue Book on organic nomenclature says:

The principal chain has the greater number of skeletal atoms.

Thus, chain length takes precedence over unsaturation.

Structure

We name your compound as a substituted pentane.

The #"CH"_2"="# group is methylidene, so the PIN (Preferred IUPAC Name) is now

2-methyl-3-methylidenepentane.