L38 - NMR And MRI: Interpreting NMR Data

Question 1

What are the 3 kinds of data which are considered for 1H NMR?

Answer 1

• chemical shift data - types of protons
• integrals - ratio of each kind of proton
• 1H-1H coupling - protons near proton in interest

Question 2

What is chemical shift equivalent?

Answer 2

If there is an element of symmetry in the molecule = symmetric atoms are chemically equivalent

Question 3

What does topicity describe?

Answer 3

Sterochemical relationship of 2 or more atoms is a molecule

Question 4

What are the different types of topicity?

Answer 4

• homotopic
• enantiotopic
• distereotopic
• heterotopic

Question 5

What are homotopic and enantiotopics protons like?

Answer 5

Resonate at the same frequency

Question 6

What are diastereotopic and heterotopic protons like?

Answer 6

Resonate at different frequencies

Question 7

How do diasterotopic and heterotopics appear?

Answer 7

At different ppm values, experience a difficult chemical environment

Question 8

How do you compare the strucutres to determine relationship for any two protons?

Answer 8

• identical - protons are homotopic
• enantiomers - protons are enantiotropic
• diastereomers - diastereotopic
• structural isomers - heterotopic

Question 9

What are integrals?

Answer 9

height
- proprotional to intensity = ratio for each kind of proton

Question 10

What is 1H-1H coupling?

Answer 10

• neighbouring protons orient with/against magnetic field of NMR instrument
• HB reinforces HA = stronger field
• HB opposes HA = weaker field
• = 2 signals = doublet
• more lines when more protons

Question 11

What are the spiltting patterns of neighbouring protons?

Answer 11

• 1 - singlet
• 1 1 - doublet
• 1 2 1 - triplet
• 1 3 3 1 - quartet
• 1 4 6 4 1 - pentet
• 1 5 10 10 5 1 - sextet
• 1 6 15 20 15 6 1 - septet