Analytical techniques: infrared spectroscopy and mass spectrometry

Learning objectives

Identify functional groups such as O–H in alcohols and in acids, N–H, C=O, C≡N and C–O from the absorption ranges in an infrared spectrum, using the data table

Calculate the relative atomic mass of an element as the abundance-weighted mean of the isotopic masses read from a mass spectrum, and deduce Mr of an organic compound from its molecular ion (M⁺) peak

Suggest the formulae of fragment ions from their m/e values (e.g. 15 CH₃⁺, 29 C₂H₅⁺ or CHO⁺, 43 CH₃CO⁺) and use fragmentation to tell isomers apart

Use the [M+1]⁺ peak to find the number of carbon atoms, n = 100 × abundance of [M+1]⁺ ÷ (1.1 × abundance of M⁺), and use [M+2]⁺ peaks to show that chlorine or bromine is present