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Response Details:
In response to VC's post, yes, that's the right way to think about it in order to get the right answer, but do be careful how the structure is drawn. The two cyclohexyl groups should not be merged together, but should be separate rings. Link and Jesley above do have it right
1. Look for the backbone structure of 3,5-dicyclohexylnonane. And that's correct, it should be a nine carbon alkane.
Meth=1
Eth=2
Prop=3
But=4
Pent=5
Hex=6
Hept=7
Oct=8
Non=9
Dec=10
2. Cyclohexyl indicates that it's a six membered ring substituent. Of course, do note that the ring is not fused into the backbone chain either, but rather, it sticks out
3. Di-cyclohexyl should tell you that there are two of these such substituents. 3,5 tells you where each of them are, at the 3, and the 5 position. Seeing as how this is a simple alkane, it doesn't matter which end of the alkane you start counting from, so long as you stay consistent.
One thing I want to add. On most o-chem exams, be prepared to not only draw a structure given the name, but to also name a compound if you're given the structure.
If you haven't learned already, there are rarely any organic compounds
that are two dimensional the way they're drawn on paper. There's all
sorts of three dimensional twisting going on, especially with alkanes.
So while it's neater to write the alkane as a straight chain, that's
hardly ever the reality.
Thanks! Keep those questions coming!
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