BRAINCAKECombining Techniques to Deduce Structures
No single technique proves a structure. In exam questions you combine evidence from several:
• Elemental analysis (percentage composition) gives the empirical formula.
• Mass spectrometry: the molecular ion peak, M+, gives the relative molecular mass, and so the molecular formula. Fragment peaks show parts of the molecule.
• Infrared spectroscopy identifies functional groups: C=O 1630-1820 cm-1, broad O-H of a carboxylic acid 2500-3300 cm-1, O-H of an alcohol 3200-3600 cm-1.
• 13C NMR gives the number of different carbon environments and their types.
• 1H NMR gives the number of proton environments, their types (δ), the ratio of protons (peak areas) and the neighbouring protons (splitting).
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
Key terms in this lesson
- empirical formula
- A formula that shows the simplest whole-number ratio of atoms of each element in a compound.
- molecular formula
- A formula that shows the actual number of atoms of each element in a molecule.
More in NMR Spectroscopy
- Deuterated Solvents
- 13C NMR Spectroscopy
- Interpreting 13C NMR Spectra
- 1H NMR Spectroscopy
- Relative Peak Areas
- Spin-Spin Splitting
- The n+1 Rule
- Identifying O-H and N-H Protons with D2O
All 12 lessons in NMR Spectroscopy · All OCR A-level Organic Chemistry topics