6 Combined techniques

Bringing it all together Elemental analysis C 66.63% H 11.18% O 22.19% 66.63/12 1. Work out empirical formula 11.18/1 22.19/16 C H O =5.5525 =11.18 =1.386875 =4 =8 =1 2. Using molecular ion peak m/z value from mass spectrum calculate Molecular formula molecular ion peak m/z value= 144 Mr empirical formula C4H8O = 72 If Mr molecular formula 144 then compound is C8H16O2 3. Use IR spectra to identify main bonds/functional group C8H16O2 could be an ester, carboxylic acid or combination of alcohol and carbonyl. Look for IR spectra for C=O and O-H bonds 4 3 2 1 5 δ ppm 2 2 3 9 C=O C-H There is a C=O but no O-H absorptions, so must be an ester. 4. Use NMR spectra to give details of carbon chain 4 peaks – only 4 different environments. singlet of area 9 At δ =0.9 Means 3 CH3 groups C CH3 H3C CH3 Peak at δ 4 shows H–C–O Area 2 suggests CH2 Quartet means next to a CH3 O C H H H Peak at δ 2.2 shows H–C=O Area 2 suggests CH2 Singlet means adjacent to C with no hydrogens O C H H C O H Peak at δ 1.2 shows R-CH3 Area 3 means CH3 Triplet means next to a CH2 CH3 Put all together to give final structure