Question

4-Methyl-cyclopentene

Answer 1

@abb0t
since the counting of carbon is clock-wise, do I start where the double bond is located when a constituent is involved?

Answer 2

4 methy-cyclopentene doesn't make sense. It should be 3-methyl cycopentene or 2-methyl-syclopentene. there is only 5 carbons in a cyclopentane ring, and double bond takes priority. 4 position would make it 2 position, since you always want lowest numbering.

Answer 3

without the constituent methyl, this would have been just 3-cyclopentene?

Answer 4

No. Just cyclopentene.

Answer 5

It's assumed that the double bond is #1 since it has priority.

Answer 6

But, it wouldn't be wrong to also say 1-cyclopentene.

Answer 7

okay, so cyclic alkenes do not follow the regular alkene nomenclature?

Answer 8

oh wait, nvm. 4-methylcyclopentene is correct. Lol.

Answer 9

I am reading the molecule wrong. Sorry. LOL.

Answer 10

why is the stupid book saying that it is 4-Methyl-cyclopentene? laughing out loud this crap confused the crap out of me

Answer 11

No, they are right.

Answer 12

isn't that counter-clockwise?

Answer 13

Yeah. You could also read it the other way around:

Answer 14

Makes no difference.

Answer 15

Sorry about the confusion.

Answer 16

oh okay, so the counting of carbon if constituents are involved starts on the double bond?

Answer 17

Yessir. double bonds > methyl substituents.

Answer 18

thanks man, I am not sure if the book mentioned this and I just missed it. It just says that it follows the alkene nomenclature... and a few additions

Answer 19

I bookmarked this site long ago. I still refer to it when I forget IUPAC priority of substituents and stuff. http://butane.chem.uiuc.edu/cyerkes/Chem104A_BFA05/Genchemref/nomenclature_rules.html

Answer 20

@abb0t I am reading the contents of the link you provided me. the number 5 rule of the unsaturated alkane and alkene would make the counting of the carbon not start from where the first double-bond is located.

Answer 21

Is that what you're talking about?

Answer 22

yeah

Answer 23

In the molecule you provided, it does. Since it is not directly attached to the cdouble bond itself. It's on a different carbon. I think that's what you're asking.

Answer 24

oh okay

Answer 25

nomenclature can get pretty confusing

Answer 26

Yeah :/
just have to practice. that's all you can do. there's loads of great sites with practice problems. It can get very difficult fast.

Answer 27

one more thing, @abb0t
the ethylhexane in the attachment I provided can be also indicated as 3-Ethylhexane?

Answer 28

the only reason I asked is that if that happened to be a heptane instead and the location of the constituent is in the 4th carbon, it will make it 4-Ethylheptane no matter how you flip and rotate the molecule

Answer 29

3-methylhexane*

Answer 30

longest chain is your suffix :)

Answer 31

For instance, 2-ethyl-1,1,3,3-tetramethylcyclopentane

Answer 32

or

Answer 33

sorry, yeah 4-methylheptane (7 carbons... I was stuck thinking about 6)