Spectrometry

Question 1

Mass spectrometry

Answer 1

Used to identify molecular mass of organic compound
Understand the structure

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

Question 2

Molecular mass from a mass spectrum

Answer 2

M+ peak, molecular mass

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

Question 3

Fragmentation

Answer 3

Same molecular ions broken down into fragments, ions

Simple fragmentation breaks ion into cation and radical

Question 4

How to identify fragments

Answer 4

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

Question 5

Using M and M+1

Answer 5

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

Question 6

Infrared radiation and covalent bonds

Answer 6

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

Question 7

Infrared radiation and atmospheric gases

Answer 7

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

Question 8

IRS, organic molecules

Answer 8

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

Question 9

Infrared spectra of common functional groups

Answer 9

Tables show ranges of each bond

Given to you

Question 10

Application of IRS

Answer 10

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

Question 11

Summary

Answer 11

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