Structural Analysis

C, H, S and N

The empirical formula is the simplest whole number ratio of the different atoms in a compound

Mass spectrometry

• The sample is firstly vaporised and then ionised by being bombarded with electrons
• Fragmentation can occur when the energy available is greater thean the molecular ionisation energy
• The parent ion and ion fragments are accelerated by an electric field and then deflected by a magnetic field
• The strength of the magnetic field is varied to enable the ions of all the different mass / charge ratios to be detected in turn.  A mass spectrum is obtained.

The molecular ion / parent ion

To identify certain functional groups in an organic compound

Infra-red radiation causes parts of a molecule to vibrate.  The wavelengths which are absorbed and cause the vibrations will depend on the type of chemical bond and the groups or atoms at the ends of these bonds.

• Wavenumber = 1 / wavelegnth = 1 / λ
• Units are cm^-1

• The different environments of hydrogen atoms in an organic molecule
• How many hydrogen atoms there are in each environment

It is a standard reference substance (which is assigned a chemical shift equal to 0)

To determine the precise three dimensional structure of organic compounds

Hydrogen

A crystal of an organic compound acts as a diffraction grating when it is exposed to X-rays of a single wavelength the atoms of the crystal act as a diffraction grating

Electron-density maps