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Flashcards in Spectrometry Deck (11)
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Mass spectrometry

Used to identify molecular mass of organic compound
Understand the structure

Loses electron, cations
Detects mass to charge ratio, molecular mass of compound


Molecular mass from a mass spectrum

M+ peak, molecular mass
Clear peak next to M+1, due to 1.1 % of C13



Same molecular ions broken down into fragments, ions
Simple fragmentation breaks ion into cation and radical


How to identify fragments

15- CH3
29- C2H5
43- C3H9
57- C4H9


Using M and M+1

No of carbon= M+1 height/ M height x 100


Infrared radiation and covalent bonds

Covalent bonds vibrate naturally, increase with temp
Bond absorbs IR, bends/stretches, change bond angle
Depends on mass, strength of bond
Heavier, weaker, vibrate more slowly
Bonds can only absorb radiation of same frequency,
Wave number directly proportionally to frequency


Infrared radiation and atmospheric gases

Atmospheric gases unaffected by IR, most of it reabsorbed by ground
Remitted at atmosphere as longer wavelength IR, eg GHG


IRS, organic molecules

Identify functional groups in molecule
IR beam passed through sample
IR frequency absorbed, emerging radiation analysis do
Transmitance/ wavenumber plotted

Fingerprint region contains unique peaks and can be used to identify molecules


Infrared spectra of common functional groups

Tables show ranges of each bond
Given to you


Application of IRS

Pollutants identified by IR fingerprint region
Remote sensors analyse IR of emissions to analyse pollutants
Breathalysers to identify bonds in ethanol



Elemental analysis, % composition, empirical formula
Mass spec, molecular mass
IRS, bonds, functional groups