Alkane Nomenclature

[susanbamboozlin]

I am having some trouble with naming alkanes. I think I did the first two problems correctly, but I am not sure. I am having some trouble with the third one, and would greatly appreciate any help you can offer. I would like to have an explanation along with the answer so I can see what I did wrong! Thanks very much!

1. (CH3)2CHCH(CH3)2
4-carbon chain makes it butane
the branches at both C2 and C3 are methyl
so the name is 2,3-dimethylbutane

                         CH2Ch2CH2CH3
                         l
CH3CH2CH2CHCH2C--H
                l         l
            CH3CH2   H
6-carbon chain makes it hexane
branch at C2 is butyl
branch at C3 is ethyl
so the name is 2-butyl-3-ethylbutane.

3. This is the one I am very unsure of:
                      CH3 H
                        l    l
CH3CH2CH2CH2--C--C--CH2CH3
                        l     l
                       CH2 CH3
                        l
                       CH3

8-carbon chain= octane
branch at C3 is methyl
branches at 4C are methyl and ethyl
That is where I get stuck on the name. Is it 4-ethyl-4,3-dimethyloctane??

Thank you very much for your input!

[freezard7734]

The first one is correct. However, in the second one, you should use the longest C-branch as the base. There is a chain much longer than 6 carbons.
Actually, your third one seems fine...

[bhavna]

Frist one is correct. Second ans should be, by selecting longest C chain which is decane; so it should be named as 4 ethly decane.
Thrid ans should be 3,4-dimethyl-4-ethyloctane, coz we should always select frist longest C chain & then numbering for groups should be in ascending orders as 1,2,3... & not as 3,2