[deutdeut]

But isn't it still weird to count the same group of atoms 2 alkyl groups? And can we simply ignore this fact as I feel so uncomfortable of this?

[Mitch]

You're the one who brought it up.

[deutdeut]

But don't you think it's weird that the same alkyl group is counted twice just from opposite directions?

[english]

*slams head on desk*

 

You really prod a lot.


It's important to consider the entire group in both directions because this can lead to different physical properties when you substitute the ring.  

We don't really refer to groups of just regular cyclohexane, because it's the same in both directions.  But if it were different, like the disubsituted example above, then this can...cause certain interesting things.  Maybe an ethyl group is next to our chosen carbon in one direction, but not in the other direction.  Well, that ethyl group can stabilize that carbon, if it is a carbocation for example.  But on the other side of the carbocation there is no ethyl group, let's say.  So counting one direction as an alkyl group and the other as a separate one is significant.

That's the best I can put it.


Take it or leave it. 

[deutdeut]

But any specfiic examples is that there is one ethyl group in one direction but not in another?

[english]

But any specfiic examples is that there is one ethyl group in one direction but not in another?

[deutdeut]

The carbon bonded to the bromide, Br, has two alkyl groups, —CH2CH(CH3)CH2CH2CH2—  and   
—CH2CH2CH2CH(CH3)CH2— , why are these groups different? What are their respective names? Thanks!

[english]

The carbon bonded to the bromide, Br, has two alkyl groups, —CH2CH(CH3)CH2CH2CH2—  and   
—CH2CH2CH2CH(CH3)CH2— , why are these groups different? What are their respective names? Thanks!

Well for one you have a methyl group coming off of a 2-carbon in one and a 4-carbon in the other, if you count from left to right.

[deutdeut]

So, what are their respective names?

[Mitch]

Dude, you're analyzing a problem at way too low a level and of course it doesn't make sense. You're arguing semantics saying a cycloalkyl group shouldn't count twice. But you need to look deeper at what a secondary carbocation means. A secondary carbocation will have general thermodynamic and kinetic effects that are unique to secondary carbocations. Guess what, a carbocation in cyclohexane, behaves exactly as one would predict a secondary carbocation would react. If it reacts like a secondary carbocation and it looks like a secondary carbocation, it is a secondary carbocation. You'll just have to get over the fact that the left hand side is the same as the right hand side and delve into a more interesting chemical question that deserves your attention.