Multinuclear NMR Spectroscopy

Question 1

Spin

Answer 1

I

Question 2

Nuclei with both p and n even

Answer 2

Zero spin so not NMR active

Question 3

Nuclei with both p and n odd

Answer 3

Whole number spin

Question 4

Nuclei with odd mass

Answer 4

Half integral spin

Question 5

Separation between energy levels

Answer 5

ΔE/h = (gβnBo)/h Hz
H = plancks constant
G = factor characteristic of each nuclei, dimensionless
βn = nuclear magnetron, JT-1
Bo = strength of external magnetic field, T

Question 6

Population of energy levels

Answer 6

Given by Boltzmann: Nupper/Nlower = exp(-ΔE/kT)
K = Boltzmann constant

Question 7

Why is NMR relatively insensitive

Answer 7

Nuclei spins almost evenly distributed, very few ‘net’ upward transitions

Question 8

Receptivity

Answer 8

Do, measure of NMR signal strength for specific isotope

Question 9

Dp

Answer 9

Receptivity compared to H

Question 10

Dc

Answer 10

Receptivity compared to C

Question 11

Quadrapolar nuclei

Answer 11

I > 1/2 have quadrapole moment, Q
Quadrapole nuclei don’t see each other in NMR

Question 12

Number of signals for I=1/2 nuclei

Answer 12

n+1 where n=number of lines

Question 13

Number of lines for quadrapolar nuclei

Answer 13

2nI+1