Environments in cyclic molecules

[Martoman]

Specifically STAV 08: question 7 in the multichoice............ please explain.


Also. Just in general, benzene will have how many peaks on H NMR and C NMR?  i count 4 but am not sure on this. If someone could explain the logic behind cyclomolecules and the nuclear magnetic stuff that would be great.

[Amino Acid]

I think in benzene, every carbon and every hydrogen are in exactly the same environment so one peak each?

Question 7

What I do if there are functional groups attached to a cyclic molecule is look at the distance between the functional group and the carbon. For example, in cyclohexanol (A), one peak for the COH, the next two adjacent carbons (on either side), then the next 2 and so on. The only cyclic molecule with three peaks is B.

[Martoman]

See im thinking D because the carbons attached to the OH are equivalient as are the two carbons flanking each one. Thats how i count 3 for that one.

[olly_s15]

D would be the first one i would eliminate - you can easily see there are two proton environments: the H in the OH groups, and all other H.

EDIT: never mind just realised it is 13C

[Amino Acid]

but in D, the 4 carbons in the middle are identical so only 2 peaks

[olly_s15]

D would be the first one i would eliminate - you can easily see there are two proton environments: the H in the OH groups, and all other H.

EDIT: never mind just realised it is 13C

quoting myself but whatev's

D is still easy to eliminate because the 4 carbons not attached to the OH are all subject to the same environment. The other two that are attached to the OH are in the same environment.

hence 2 peaks

[Martoman]

Thanks guys.