Mass Spectrometry  Determine the Molecular Mass of organic compounds.  Determine the Molecular Formula of organic compounds.  Sometime identified the functional groups in organic compounds. The main use of Mass in organic chemistry is: 1

Mass Spectrometer Sample Inlet system Ionization Chamber Mass Analyzer Detector 2

There are three kinds each of which we will consider each of these separately: Mass Spectrum  Molecular ion  Fragments  Natural abundance of isotopes 3

Molecular ion Separate the Ions according to their Mass-to-Charge ratios (m/e) 4

Cyclohexane 5

n-Octane 6

2-Methylpentane 7

Isotopic Abundance 81 Br 8

Mass Spectrum with Bromine 9

Mass Spectrum with Chlorine 10

طيف الكتلة للمركبات العضوية الشائعة Hydrocarbons m/e = 43 m/e = 29 m/e = 43 m/e = 57 11

Mass Spectra of Alkanes 12

Mass Spectra of Alkanes More stable carbocations will be more abundant. 13

Cycloalkane m/e = 42 14

m/e = 56 m/e = 69 m/e = 41 Cycloalkane 15

Alkene allylic cleavage m/e = 41 16

Cycloalkene m/e = 54 17

Alkyne β- cleavage m/e = 39 18

Aromatic Hydrocarbons 19

Aldehydes and Ketones Aldehyde α - cleavage 20

Ketone α - cleavage 21

McLafferty rearrangment 22

Carboxylic acids and Deriv. 23

Amines β - cleavage 24

Alcohols β - cleavage 25

Phenol 26