Naming hydrocarbons

Question

-what is the name of the alkyne that is present in the question 3 b?

-what is the name of the cyclic hydrocarbon that is present in question 4b?

-How do you name each of them and what is the specific name that can be shown in each?

-Please help. Thanks.

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Answer 1

Hi Jenny F.,

You should get familiar with the IUPAC naming rules; they're laid out in great detail to systematically address all your possible naming concerns!

Basically, for 3b, the longest carbon chain, that includes the greatest number of simplest modifications (explained below) is selected. Modifications include bond multiples, heteroatoms, and side chains. Here, a 7 carbon chain can be selected that includes the -ene, at the lowest number position. That's a hept-1-ene, therefore. The next choice is what to do at the left end: take the route out with an ethyl at C-5 and a methyl at C-6 or take an isopropyl at C-5? I believe (though I'm not sure!) that the former is correct, b/c the C-5 substitutent is less complex that way. I think you should be able to number carbons and take it from there?

Likewise for 4b, the choice is between the -ene of the ring and the methyl for numbering precedence. I believe (again!) that the -ene takes precedence, so the ene would be between C-1 and C-2, and the methyl at C-3, for final name 3-methyl-cyclohex-3-ene.

But, you should get access to an online CRC handbook for chemistry or an online IUPAC naming rules list, and check out these assessments, yourself.

-- Cheers, -- Mr. d.