Chapter 17

Question 1

How does mass spectometry work?

Answer 1

1) organic compound placed in mass spectometer
2) organic compound loses electron + forms positive ion
3) mass spectometer detects mass-to-charge ratio (m/z)
4) gives molecular mass

Question 2

How do you find molecular mass from a mass spectrum?

Answer 2

locate molecular ion peak - clear peak at highest m/z value on right-hand side

Question 3

What does the simplest fragmentation break a molecular ion into?

Answer 3

positively charged fragment ion + radical

Question 4

number of carbon atoms =

Answer 4

(height of M+1 peak / height of M peak) x 100

Question 5

What does the amount a bond stretches/bends depend on?

Answer 5

1) mass of atoms in bond - heavier atoms vibrate slower than lighter atoms
2) strength of bond - stronger bonds vibrate faster than weaker bonds

Question 6

How does infrared spectroscopy work?

Answer 6

1) sample placed inside IR spectrometer
2) beam of radiation passed through sample
3) molecule absorbs some IR frequencies + emerging beam of radiation is analysed to identify frequencies absorbed by sample
4) IR spectrometer connected to computer that plots graph of transmittance against wavenumber