Still don't understand where i went wrong. thought there are 2
carbon chains for (b) so isn't it ethyl? ok, how exactly does 1 C
chain look like? From what i see in the diagram drawn, as long as i
see 2 C atoms sticking out of the longest branch, it's considered 2
C chains. Not sure if i perceived it correctly.thanks
Now u need to understand that the longest chain or main chain
does not always mean it must be a straight chain.
C - C - C - C
|
C - C
This is a hexane not a ethylbutane. The 6C are still consider the
same chain if u redraw and align them together. The line looks
longer due to font constrain.
C - C - C - C -
C
C - C
- C - C - C
|
|
C -
C
C - C
Now base on the above explaination, this is a methylhexane since the hexane is the
longest chain (red) and not a ethylpentane (blue).
Do u understand this now? If you don't, don't read further and
just tell me you don't understand and i'll try explain.
If u can understand this, we'll go on to the last bit of your
naming to make a) correct since methylpentane is still not fully
correct.
--------------------------------------------------------------------------------------------------------
C - C - C - C -
C
C - C - C - C - C
|
|
C
C
Now both the above are methylpentane but are they the same
compound?
Since the 2 structures are drawn differently, they are
chemically different so how do people differentiate them so we know
which is being referred to? We do this by numbering the location of
the side chains which is methyl in this case.
1C - 2C - 3C - 4C -
5C
|
C (methyl)
Now this methyl is on carbon 3 so we will call it 3-methylpentane.
(Take note that its always a number - compound name, NOT 3,methylpentane,
3.methylpentane etc)
In the above example, whether we count from the left or right,
it would be 3 but how about this case?
1C - 2C - 3C - 4C - 5C
OR
5C - 4C - 3C - 2C - 1C
|
|
C (methyl)
C (methyl)
Should the answer be 4-methylpentane or 2-methylpentane?
In organic chemistry, we will always name it with the smaller
number choice so the answer will be 2-methylpentane.
Do note that the below 2 are exactly the same
5C - 4C - 3C - 2C - C (methyl)
5C - 4C - 3C - 2C - 1C
|
|
1C
C (methyl)
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If you have understand everything up to here, please try to now
give the correct answer for b) and c) with the proper naming
style.