Mass spectra and infrared spectroscopyEdexcel International A Level Chemistry: Mind map

Exam questions on Mass spectra and infrared spectroscopy

1. A compound X contains carbon, hydrogen and oxygen only. Its mass spectrum has a molecular ion peak at m/z 58, the largest fragment peak at m/z 43, a small peak at m/z 15 and no significant peak at m/z 29. Its infrared spectrum has a strong absorption at 1715 cm⁻¹ and no absorption above 3000 cm⁻¹.
   Give the formulae of the ions responsible for the peaks at m/z 43 and m/z 15.2 marks
2. A liquid Z has an infrared spectrum with a very broad absorption between 2500 and 3300 cm⁻¹ and a strong, sharp absorption at 1710 cm⁻¹. Its molecular ion peak is at m/z 74.
   A student suggests that Z is an alcohol. Use the infrared data to explain why this is not correct.2 marks
3. A compound W contains only carbon, hydrogen and oxygen. Its mass spectrum has peaks at m/z 74, 57, 45 and 29, with the peak at m/z 74 the molecular ion. Its infrared spectrum has a very broad absorption at 2500 to 3300 cm⁻¹ and a strong absorption at 1710 cm⁻¹.
   Use the infrared data to deduce the functional group in W and state the evidence for it.3 marks