H-NMR

NMR is based on
nuclei magnetic moments that can either align with the field or against the magnetic field.
what does the alpha state refer to?

nuclei whose mag moments align with the field.

 

(alpha= align)

what does the beta state refer to?

nuclei whose mag moments align against  the field.

 

 

alpha vs beta state who has higher energy
beta state

nmr uses a variable of measurment called______

with units called _____

chemical shifts (?)

units:  parts per million (ppm)

the chemical shift increases in what direction ,

 

this is called ____ field

to the left

 

(called downfield)

NMR usually is on what nuclei (2)

 

does  12C  have magnetic moments?

1H & 13 C

 

12 C (does not have magnetic moments)

what does it mean when it says the proton that is being deshielded?

dieshieled means:

the proton is next to an electronegative atom (which is pulling electron density from the proton) thus deshielding it from its own electron cloud)

protons that are being deshielded would appear more to the left or right?

more to the left.

(aka more downfield)

H-Cl vs H-NH2

would one would appear more to left

include why

H-Cl : more on the LEFT b/c Cl is electrongetive & e- WITHDRAWING

= proton dishielded

 

H-NH2: NH2 is an e-donating group

and thus shields the proton

 

when does splitting or coupling occur?
when 2 protons  that are in close proximity but are NOT magentically identical.

CH3 -O- CHCl2

would peak would be taller?

CH3 peak

b/c they are more of these type of protons

 

(CHCl2 just has 1 proton)

formula for determining multiplets

n+1

 

n= of H that are 3 bonds away

area of each peak is determined by
ratio of protons producing each peak
any more than 4 peaks is called
multiplet
give the range for R-CH3 protons

about 0.9

 

(most shielded)

give the range for alkyl (triple bond) protons
1-3 ppm
give the range for alkene (double bond) protons
4-7 ppm
give the range for aldehydes (double bond) protons
9 to 10 ppm
give the range for carboxylic acid (double bond) protons

10 to 12

 

most deshielded

give NMR shift for aromatic protons
6-8.5 ppm
give NMR shift for alcohol protons
3-5 ppm
give NMR range for vinylic
5.5 ppm
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