IR and mass spectronomy

All bonds vibrate at a characteristic frequency depending on the mass of the atoms, bond strength, and type of vibration

This is the infrared region of the electromagnetic spectrum

Infrared light will absorb some or all of the light at the frequencies at which its
bonds vibrate

'Fingerprint region'

More complicated and contains many signals so picking out functional groups is difficult

Unique for every compound

Can be compared to known samples to help identify it

Can also be checked to see if a compound is pure - should be identical. Any extra peaks are due to impurities

Identifying functional group signals

Used to spot characteristic signals for functional groups

C-H

2850 - 3000

3000 in unsaturated compounds, and <3000 in saturated compounds

O-H

very broad

carboxylic acids = 2500 - 3000

alcohols = 3200 - 3500

C=O

around 1700

aldehydes, ketones, carboxylic acids and esters

C=C

alkenes

small peak

around 1650

Mass spectronomy

Main stages

Ionisation

Acceleration

Deflection

Detection

Dalton's Atomic Theory

Elements are made of extremely small particles called atoms

Atoms of different elements can combine in whole number ratios

In chemical reactions, atoms are combined, divided, or rearranged

Used to identify atomic masses

After electron
bombardment, the majority of the ions formed have a +1 charge

Vaporisation

Fragmentation: molecular ions are broken up

Fragments may be responsible for other peaks found on the spectrum