U3-5-4 - NMR Spectroscopy

Question 1

The number of peaks in a low resolution proton NMR spectrum is equal to _____.

Answer 1

the number of different chemical environments (for H atoms) in the molecule

Question 2

In NMR spectra, peaks corresponding to different chemical environments have different ____.

Answer 2

chemical shifts

Question 3

What information do integration curves provide?

Answer 3

Ratio of H atoms in each chemical environment (equal to height ratio of integration curves).

Question 4

In high res NMR, peaks will split into multiplets. Why is this?

Answer 4

Protons on adjacent carbons interact with each other (and split the signal coming from their neighbour).

Question 5

How can you predict the no. of peaks in a multiplet? (NMR)

Answer 5

Using the n+1 rule, where n = no. of protons on neighbouring C atoms.

(3H on adjacent carbons ⇒ 3+1=4 peaks)

Question 6

How many peaks will be in the multiplet for the H circled? (NMR)

Answer 6

4 (3H on adajcent carbons)