Chemical Analysis - 1H NMR (10.8)

Question 1

What does 1H NMR show us?

Answer 1

• similar to carbon
• no. of peaks = no. of environments
• position of peak = type of functional group

Question 2

What is the peak integral?

Answer 2

• calculated by the computer + written next to/ under the peak
• area under the peak that gives info about the number of protons in that environment
• only tells you the ratio of protons in each environment
• may need to multiply this number to give the total number of protons in the molecule

Question 3

What is peak splitting?

Answer 3

• in 1H NMR, peaks are not always one sharp peak

- they sometimes split, depending on how many protons are in the neighboring environments

Question 4

What does 1 peak, singlet mean?

Answer 4

• neighboring carbon has 0 hydrogens

OR proton not attached to a carbon

Question 5

What does 2 peaks, doublet mean?

Answer 5

• neighboring carbon has 1 hydrogen

Question 6

What does 3 peaks, triplet mean?

Answer 6

• neighboring carbon has 2 hydrogens

Question 7

What does 4 peaks, quartet mean?

Answer 7

• neighboring carbon has 3 hydrogens

Question 8

How do you calculate the no. of peaks?

Answer 8

n + 1 rule, number of carbons next door + 1

Question 9

What is the effect of electronegativity on 1H NMR?

Answer 9

• the positioning of the functional groups
• the frequency of radio waves absorbed by an atom depends on the magnetic field experienced at the nucleus.
• the magnetic field experienced at the nucleus depends on the amount of electron density around the atom.
• an electronegative atom pulls valence electrons away from the atom and effectively decreases the electron density around the nuclei.