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proton Nmr how to read cycloalkanes

Hey guys I am struggling to read cyclohexane on an nmr espectially when a group is attached to them
What don’t you get? Is it the symmetry?
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googie3
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Original post by Stormragexox
Hey guys I am struggling to read cyclohexane on an nmr espectially when a group is attached to them


first see how many chemical environments. ..send question
are we talking low temperature conformational analysis or room temperature structural anaysis?
Original post by googie3
first see how many chemical environments. ..send question

Thank you for replying XD its not really a question my teacher was just mentioning an example of his own in class. He was talking about how many peaks form in an nmr for 1,6 dimethyl cyclohexane but i don't know how to visualize the neighboring hydrogen in the ring of cyclohexane like i do with alkane chains with branches... I have the same problem doing this with benzene too when a functional group is attached to it i can't really interpret it on the nmr as well
Original post by MrMoment
What don’t you get? Is it the symmetry?


Original post by charco
are we talking low temperature conformational analysis or room temperature structural anaysis?
If an atom has all the atoms attached to it directly (and at every step further down the chain) the same then it is in the same environment - UNLESS there is a different arrangement in space bringing another atom close to it from a different part of the molecule (this exception is rare)

The trick is to consider each environment holistically, not just the atoms directly attached.

In a benzene ring every hydrogen atom is in an identical environment - attached to a carbon which is part of the hexagonal ring. It should be aapparent that all hydrogens find an identical chain of attached atoms.

BUT a mono-substituted benzene has hydrogens at positions 2 & 6 in identical environments, but different from 3 & 5 positions. These are all in a different environment to the hydrogen at position 4.

The protons at positions 2 & 6 are only 1 step removed from the substituted group on the ring, while the protons on positions 3 & 5 are two steps removed from the substituted group; the 4 position is three-steps removed.

The same argument can be used for (low-resolution) substituted cyclohexanes.

However, with high-resolution NMR, in substituted cyclohexanes you have to also take into account the conformational shape of the ring and the fact that equatorial and axial protons may be in close proximity to the substituted group. It can get complicated.
Original post by Stormragexox
Thank you for replying XD its not really a question my teacher was just mentioning an example of his own in class. He was talking about how many peaks form in an nmr for 1,6 dimethyl cyclohexane but i don't know how to visualize the neighboring hydrogen in the ring of cyclohexane like i do with alkane chains with branches... I have the same problem doing this with benzene too when a functional group is attached to it i can't really interpret it on the nmr as well

In 1,6 - dimethylcyclohexane you'll have 4 groups. The compound is symmetrical so you can see it easily. There'll be one group of the two CH3s, one group of the 2 CH2s either side of the methyls, one group of the two Hs on the carbon that the CH3s are attached to and one group of the two CH2s opposite the CH3s.

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