Infra-red spectroscopy and mass specrometry

Infra-red Spectroscopy

Bonds vibrate in 2 different ways: stretching bending

Mass Spectrometry

We use wave numbers because frequencies in Hz are often VERY LARGE. If the TRANSMITTANCE is 100%, then no radiation is absorbed. You can identify the FUNCTIONAL GROUP by reading the wave number @ a peak.

wave number= no' of waves in 1 cm (units: cm^-1)

Used to: IDENTIFY unknown compounds determine the ABUNDANCE of isotopes in an element gain info. on the STRUCTURE of molecules detect POLLUTANTS and toxic chemicals detect drugs

How it works: Ionisation- molecules become +ve ions when electron is knocked off Acceleration- molecular ions speed up Deflection- ions deflected round a bend by magnetic field. Field strength required links directly to ion's mass Detection- ions detected and info. fed to computor

m/z= mass:charge ratio (charge always 1)

Molecular ion peak: furthest peak to the right of the graphm/z value= Molecular mass

Fragmentation: excess energy causes bonds to weaken molecules split into 1 +ve ion and one neutral species ions detected neutral species aren't Isomers have the same Mr but different fragmentation patterns