[sabre2th1]

Its but- because there are 4 carbons in the longest chain. But how do I progress from here? How do I know whether the methyl group is on the third or second carbon? Also, when writing out the name of a organic compound do alkyl groups always come first?

[thegodofgod]

(Original post by sabre2th1)


Its but- because there are 4 carbons in the longest chain. But how do I progress from here? How do I know whether the methyl group is on the third or second carbon? Also, when writing out the name of a organic compound do alkyl groups always come first?

The ending of the name is going to be 'but-2-ene' no matter what.

Therefore, the whole name could be: '2-methylbut-2-ene', or '3-methylbut-2-ene', if you count from the other end.

You have to try to get the total of the numbers as low as possible, and 2+2=4 is lower than 3+2=5, so the name is '2-methylbut-2-ene'.

Alkyl- groups don't always come first, e.g. CH₃CHClCH₃ = 2-chloropropane.

[TheBigI]

And remember that side chains are listed alphabetically if you have more than one.

[sabre2th1]

(Original post by thegodofgod)
The ending of the name is going to be 'but-2-ene' no matter what.

Therefore, the whole name could be: '2-methylbut-2-ene', or '3-methylbut-2-ene', if you count from the other end.

You have to try to get the total of the numbers as low as possible, and 2+2=4 is lower than 3+2=5, so the name is '2-methylbut-2-ene'.

Alkyl- groups don't always come first, e.g. CH₃CHClCH₃ = 2-chloropropane.

Ah that clears things up! Thanks a lot..



The above molecule is prop-1-ene (or propene) rather than prop-2-ene because you always choose the smallest number possible (so in this case you count from the right)??

Cheers

[EierVonSatan]

(Original post by sabre2th1)
Ah that clears things up! Thanks a lot..



The above molecule is prop-1-ene (or propene) rather than prop-2-ene because you always choose the smallest number possible (so in this case you count from the right)??

Cheers

You don't need any numbers here, it's just propene as you can only have the double bond in one place

If it was CH₃CH₂CH=CH₂

then this would be but-1-ene as you take the lowest number possible

[sabre2th1]

(Original post by eiervonsatan)
you don't need any numbers here, it's just propene as you can only have the double bond in one place

if it was ch₃ch₂ch=ch₂

then this would be but-1-ene as you take the lowest number possible

thanks!