nomenclature of a pentane hydrocarbon...any help please?

[Mr Rayon]

c

|

c - c - c

|

c

 

Just started organic chemistry in high school. In the above diagram there are three hydrogens hanging off the four outer carbons. Is the answer 2,2-dimethylpropane or 2-dimethylpropane?

 

edit: hold on those 2 carbons- the one at the top and the one below is supposed to be attached to the middle 2nd carbon of propane but I can't draw it properly for some reason.

[Greippi]

2,2-dimethylpropane (aka neopentane, sometimes it's just called dimethylpropane). But if you're naming it systemically, you have to include the 2,2- part so it's unambiguous about exactly where those methyl groups are situated.

Edited May 11, 2010 by Greippi

[Mr Rayon]

Ok, thanks for the help!

[xxzero90xx]

Actually, according to IUPAC the longest carbon chain is the parent. Thus the name would be 2-methylbutane

[Penny]

Actually, according to IUPAC the longest carbon chain is the parent. Thus the name would be 2-methylbutane

 

Read the original post carefully. The diagram isn't what it seems...

[hermanntrude]

2,2-dimethylpropane (aka neopentane, sometimes it's just called dimethylpropane). But if you're naming it systemically, you have to include the 2,2- part so it's unambiguous about exactly where those methyl groups are situated.

 

actually the 2,2 part isn't necessary because if the methyl groups were on the 1- or the 3- positions, the parent chain would be longer and there'd be an entirely different name.

 

from wikipedia:

 

IUPAC nomenclature retains the trivial name neopentane. The systematic name is 2,2-dimethylpropane, but the substituent numbers are unnecessary because it is the only possible "dimethylpropane".

[Physicsfan]

The longest carbon chain has 4 carbon atoms. By IUPAC naming conventions the position of a functional group or in this case the methyl group should have the smallest possible integer number.

So the name should be 2-methyl Butane.

 

oops i didnt know the question had already been answered.