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# (1H NMR) Predicting chemical shifts/magnetic field orientations Tweet

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1. yeah
yeah
Last edited by 93M; 11-01-2013 at 21:48.
2. Re: (1H NMR) Predicting chemical shifts/magnetic field orientations
(Original post by 93M)
Could someone explain the "2I+1 rule" for working out how many orientations an atom will have in a magnetic field?

Also, how are chemical shifts predicted using "Schoolery's rules"?

Attempted to search online but without much luck
It's statistical.

If one H atom has two different states (and hence can provide two different environments for a neighbouring hydrogen atom)

Represent the two states as + and - (or whatever else you wish)

then two H atoms have three different (combined) states. ++ +- (-+) --

then three hydrogen atoms have 4 different states, +++ +-- (-+-, --+) ++- (+-+, -++) ---

etc.
3. Re: (1H NMR) Predicting chemical shifts/magnetic field orientations
(Original post by charco)
It's statistical.

If one H atom has two different states (and hence can provide two different environments for a neighbouring hydrogen atom)

Represent the two states as + and - (or whatever else you wish)

then two H atoms have three different (combined) states. ++ +- (-+) --

then three hydrogen atoms have 4 different states, +++ +-- (-+-, --+) ++- (+-+, -++) ---

etc.
Thank you, in my notes it says carbon-12 is (I=0) and nitrogen-14 is (I=1), how do they arrive at these numbers?
4. Re: (1H NMR) Predicting chemical shifts/magnetic field orientations
(Original post by 93M)
Thank you, in my notes it says carbon-12 is (I=0) and nitrogen-14 is (I=1), how do they arrive at these numbers?
You look them up or measure them.