What is the structure of 5,5-diethyl-2,2,3-trimethylheptane?

1 Answer
Truong-Son N.
Oct 1, 2017

I would start from the parent name, heptane. The prefix "hept" means 7, so the main chain contains 7 carbons:

color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
"H"_3"C"-"C"-"C"-"C"-"C"-"C"-"CH"_3
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|

Then I would work from right to left in the name. The 2,2,3-"trimethyl" suggests that:

  • "tri" -> three duplicate branching groups
  • "methyl" -> "H"_3"C"- groups
  • The first two are on carbon-2 and the third one is on carbon-3.

So far, we fill it in as:

color(red)(color(white)(..........)"CH"_3color(white)(.)"CH"_3)
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
"H"_3"C"-"C"-"C"-"C"-"C"-"C"-"CH"_3
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
color(red)(color(white)(..........)"CH"_3)

Lastly, we proceed to the leftmost part of the name. The 5,5-"diethyl" suggests that:

  • "di" -> two duplicate branching groups
  • "ethyl" -> "H"_3"CCH"_2- groups
  • These are both on carbon-5.

So we get:

color(white)(..........)color(white)(..........)color(white)(..........)color(red)("CH"_3)
color(white)(..........)color(white)(..........)color(white)(...........)|
color(red)(color(white)(..........)"CH"_3color(white)(.)"CH"_3color(white)(.....)"CH"_2)
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
"H"_3"C"-"C"-"C"-"C"-"C"-"C"-"CH"_3
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
color(red)(color(white)(..........)"CH"_3color(white)(..............)color(red)("CH"_2))
color(white)(..........)color(white)(..........)color(white)(...........)|
color(white)(..........)color(white)(..........)color(white)(..........)color(red)("CH"_3)

Lastly, since this is an alkane, the most saturated kind of hydrocarbon (relative to alkenes and alkynes), just fill in the rest of the branches with "H".

color(white)(..........)color(white)(..........)color(white)(..........)color(red)("CH"_3)
color(white)(..........)color(white)(..........)color(white)(...........)|
color(red)(color(white)(.........)"CH"_3color(white)(.)"CH"_3color(white)(.)"H"color(white)(...)"CH"_2color(white)(.)"H")
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
"H"_3"C"-"C"-"C"-"C"-"C"-"C"-"CH"_3
color(white)(...........)|color(white)(......)|color(white)(......)|color(white)(......)|color(white)(......)|
color(red)(color(white)(..........)"CH"_3color(white)(.)"H"color(white)(..)"H"color(white)(...)color(red)("CH"_2)color(white)(.)"H")
color(white)(..........)color(white)(..........)color(white)(...........)|
color(white)(..........)color(white)(..........)color(white)(..........)color(red)("CH"_3)

And this in reality looks like:

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