Chemical Analysis - 13C NMR (10.7)

Question 1

What is NMR spectroscopy and what does it do?

Answer 1

• uses the magnetic properties of nuclei with an odd number of nucleons (e.g. 13C 1H)
• info about the chemical environment of the nucleus

Question 2

What is a chemical environment?

Answer 2

• unique arrangement of atoms in a molecule
  e. g. CH3
• they are only identical if they are exactly the same
• depends on the identity of the groups on either side

Question 3

In which conditions are two carbons not identical?

Answer 3

• both CH2
• both next to one CH2
• one next to CH3
• other next to COOH

Question 4

What makes a molecule symmetrical?

Answer 4

• opposite carbons = identical but the blue + orange carbons = different

Question 5

When makes carbons identical?

Answer 5

• bond angle = the same

- C-C bonds can rotate

Question 6

What does the NMR tell us?

Answer 6

• the no. of peaks = no. of environments
  e. g. 3 environments = 3 peaks
• position of peak = type of functional group

Question 7

What are chemical shifts?

Answer 7

• position of the peak
• characteristic of the functional group
• measured in ppm
• given a table of their values in an exam