[english]

I just started organic chemistry and was wanton of some help with this really long straight-chain alkane.  It's an isomer of octadecane, and I need to know the IUPAC name for it.  I don't really see how my book could be correct in any sense and would like to ask you guys and then later verify with my professor as well.

The book indicates that the systematic name is 5-(2-ethylbutyl)-3,3-dimethyldecane.

Here is the image of the condensed structure for the compound so you can obviously see it:

http://i87.photobucket.com/albums/k159/abcdefg_054/lastscan.jpg

I am thankful for any help, fellow chemistry friends.

-k.V.

[Albert]

My opinion is that 5-(2-ethylbutyl)-3,3-dimethyldecane is the right IUPAC name. However, ChemDraw says its name is 3-ethyl-5-tert-pentyldecane.

[Winga]

5-(2-ethylbutyl)-3,3-dimethyldecane is correct.

Choose the main chain with the smallest no. of sub-branches.

[english]

5-(2-ethylbutyl)-3,3-dimethyldecane is correct.

Choose the main chain with the smallest no. of sub-branches.

You're supposed to choose the longest chain with the most sub-branches.  This is the only way we arrive at 5-(2-ethylbuty)-

Now I see where that part is coming from.  But the lower branch of the number 5 carbon is where I'm confused.  There are 3 methyl groups here, as well as an additional ethyl group.  But the name implies only two methyl groups and only one ethyl group, the one bound to the butyl group.

 

[Winga]

I mean...a sub-branch = a branch of a branch

Getting the maximum no. of branches will minimize the no. of sub-branches.

[Winga]

But the lower branch of the number 5 carbon is where I'm confused.  There are 3 methyl groups here, as well as an additional ethyl group.  But the name implies only two methyl groups and only one ethyl group, the one bound to the butyl group.

The lower branch you mentioned should be a part of the main chain not a branch. So, 3,3-dimethyl- is to describe the two methyl groups attach the carbon no.3.

[xiankai]

the condensed structural formula may be misleading; check out the full structural formula.

PS: i changed the structure appropriately

[english]

the condensed structural formula may be misleading; check out the full structural formula.

I see my problem now.  Since the longest chain starts at the ethyl group at the very bottom and proceeds up and left, giving us decane as the parent, only those two methyl groups branching off of carbon 3 matters.  See I was thinking that it was supposed to be 3,3,3,3-trimethyl ethyl ethyl(?)  but that makes no sense at all.

It's all because those carbons in that branch are part of the parent chain.  doh!

btw thanks for the skeletal structure xiankai