NMR

Question 1

What is running spectra?

Answer 1

• liquid sample placed in long, thin tube, spinning in a magnetic field
• solids are dissolved in solvents that won’t affect the spectrum - CDCI3

Question 2

What is added to provide a reference signal and why that specifically? (TMS)

Answer 2

(CH3)4Si
(tetramethylsilane, TMS)

• produces a single, intense peak
• signal is outside of the range shown by most protons
• is inert, non-toxic, and has a low BP - can be distilled off if required

Question 3

What is multiplicity/spin coupling

Answer 3

Occurs when the spin of one nucleus affects a different nucleus of an adjacent atom

Question 4

Explain reading a 13C NMR graph

Answer 4

1. Number of signals = number of carbon environments
2. Use the chemical shift to work out functional groups

Question 5

Explain reading an 1H NMR graph

Answer 5

1. Number of signals = number of hydrogen environments
2. peak area/distance between integration lines = number of hydrogens in an environment
3. number of peaks in a signal is one more than the number of hydrogens in an adjacent hydrogen environment (n+1)

ex. 1 peak means there are 0 neighbouring hydrogen environments