[Evaldas]

We were assigned to write (and draw) all the isomers of heptine (C₇H₁₂), and I would like to know how many are there?

[Dan]

Wouldn't we all? Please show you have attempted the question.

http://www.chemicalforums.com/index.php?topic=33740.0

[Evaldas]

My gosh... I'm just asking for a number. I know how to write the isomers, I just need to know how much there are. Right now I already have 1-heptine, 2-heptine, 3-heptine, 3-methyl-1-hexyne, but I know there's still dozens.

[sjb]

Do you mean just alkyne isomers, or will e.g. dienes, cyclic enes, bicycles also do?

[Evaldas]

Just alkyne.

[Evaldas]

I THINK just alkyne. You be the judge: it's my third year of chemistry and about the tenth lesson of organic chemistry.

[sjb]

I THINK just alkyne. You be the judge: it's my third year of chemistry and about the tenth lesson of organic chemistry.

Well, to me, a third year should include things like dienes, cyclic enes, bicycles, perhaps even things like carbenes, but I'm concious that things may not translate to your situation.

For what it's worth, I only make it 15 alkyne isomers. Consider isomers of things like the pentyl, butyl, propyl radicals, and don't forget stereochemistry

[Evaldas]

I'm not really sure how to name this isomer:

2,3-metyl-5-pentine or 3,4-metyl-1-pentine?
Because according to the rules I'm supposed to:
Find the longest C atoms chain;
Number the C atoms starting from the end where the radical(s) is/are closer to - so I'd have to start numbering from right to left.
BUT ALSO I have to number C atoms starting from the end where the triple bond is the closest - and in this case I'd have to number from left to right.
So I'm confused: how do I number the C atoms in this one?

Speaking of radicals I think I should combine not just pentyl, butyl, propyl, but as well metyl, etyl, right?
And etyl radical would be C2H5, propyl C3H6, butyl C4H7, right?

[sjb]

To be pedantic, neither is the correct name, but I think the second is closer to the truth. I believe that the yne has priority here.

Yes, you also have to take into account methyls, ethyls and protons, but there is not any isomerism here. Check your formulae for the ethyl, propyl and butyl radicals

[Evaldas]

I've checked with my teacher about that isomer and it's 3,4-dimetyl-1-pentine (or whatever's the spelling), because you have to start numbering from where the triple bond is closer to the end of the longest C atoms chain, because the triple bond is higher in the hierarchy than the radical.

[sjb]

Did you also check to see if you're required to include other functional groups than alkynes?

[Evaldas]

Did you also check to see if you're required to include other functional groups than alkynes?

Only heptine isomers. And only today we were taught about dienes and etc.

[AWK]

Did you also check to see if you're required to include other functional groups than alkynes?

Only heptine isomers. And only today we were taught about dienes and etc.

Did you get a number close to given by SJB?

[Evaldas]

Did you also check to see if you're required to include other functional groups than alkynes?

Only heptine isomers. And only today we were taught about dienes and etc.

Did you get a number close to given by SJB?

Not really, I stopped at that one I've asked before about, and when I cleared that out, I wrote a few more and stopped, because it was past the assignment.