Organic chemistry? (chemistry fundamentals)

[Starlight]

How do you draw 3-isobutyl hexane???

The answer says (see attachment 9a and also 9d)



I dont understand how the longest chain is 7 carbons long when the questions says 'hexane'

Also what is an iso group?

[jasoN-]

Yeah 3-isobutylhexane is the structure you have at (a)
The correct name (IUPAC nomenclature) would be 4-ethyl-2-methylheptane as written in (d)
I think the question is really just trying to show you what the isobutyl group looks like, which is in (a); R-CH2CH(CH3)2

[Starlight]

Ah sorry i still don't get it. If 3-isobutylhexane is at a, why is it that it has 7 carbons for it's longest chain rather than 6 carbons in it's longest chain considering it says 'hexane'?

[jasoN-]

Yeah the naming is just non-systematic.
As in, they're trying to express the substituent 'isobutyl' on a carbon chain 'hexane'
The correct name (and I think this is why it's confusing you) would be 4-ethyl-2-methylheptane.

3-isobutylhexane still is a name for that structure, but it's just not the sytematic name.
Another example would be something like 2-propylpentane rather than 3-methylhexane, they're both names to describe one specific structure, it's just one is the correct (systematic) name (the latter of the two).