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Mass Spectrometry: Fragmentation of Ethers, Sulfides, Amines, Carbonyls, and Functional Gr, Lecture notes of Chemistry

Pickaway Ross Joint Vocational School DistrictChemistry

An overview of mass spectrometry fragmentation patterns for various functional groups, including ethers, sulfides, amines, and carbonyl compounds. It covers fragmentation modes such as α-cleavage, inductive cleavage, rearrangement, McLafferty rearrangement, and loss of functional groups. The document also includes specific examples of fragmentation for various ethers, sulfides, amines, and functional groups.

What you will learn

  • What is the fragmentation pattern for ethers in mass spectrometry?
  • What is the fragmentation pattern for sulfides in mass spectrometry?
  • What is the difference between α-cleavage and inductive cleavage in mass spectrometry?
  • What is the difference between aliphatic and aromatic amines in mass spectrometry?
  • What is the McLafferty rearrangement in mass spectrometry?

Typology: Lecture notes

2021/2022

Uploaded on 09/12/2022

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Mass Spectrometry: Fragmentation
Ethers & Sulfides !!!!!
Ethers
• M+ usually stronger than corresponding alcohol; may be weak/absent
• α-cleavage of an alkyl radical
• Inductive cleavage
• Rearrangement with loss of CHR=CHR’
Aryl Ethers
• M+ strong
• C-O cleavage β to aromatic ring with subsequent loss of CO
• Cleavage adjacent to aryl ring also possible
Sulfides
• M+ usually stronger than corresponding ether
• cleavage pattern similar to ethers
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Download Mass Spectrometry: Fragmentation of Ethers, Sulfides, Amines, Carbonyls, and Functional Gr and more Lecture notes Chemistry in PDF only on Docsity!

Ethers & Sulfides!!!!!

Ethers

  • M+^ usually stronger than corresponding alcohol; may be weak/absent
  • α-cleavage of an alkyl radical
  • Inductive cleavage
  • Rearrangement with loss of CHR=CHR’

Aryl Ethers

  • M+^ strong
  • C-O cleavage β to aromatic ring with subsequent loss of CO
  • Cleavage adjacent to aryl ring also possible

Sulfides

  • M+^ usually stronger than corresponding ether
  • cleavage pattern similar to ethers

Ethers

fragmentation patterns

α -cleavage inductive cleavage rearrangement

R CH 2 O R' O

H

H

R'

R +

R CH 2 O R' R^ CH 2 + O^ R'

O

CH 2

H

H

CHR

H

+ H 2 C=CHR

O

H

H

H

Ethers

di- sec -butyl ether

O

MW = 130

M (130)

M-

M-

O H CH 3 CH 2 O H H 3 C m/z = 59 m/z = 45 O H H H 3 C O H H CH 3 CH 2 m/z = 57

Ethers

2-ethyl-2-methyl-1,3-dioxolane

O O

MW = 116

M-

M-

M+^ absent O O O O

Aryl Ethers

fragmentation of aryl ethers

O

CH 2

H

m/z = 78 m/z = 77

O

CH 2

H

H

H

- CH 2 O - H

O CH 3 m/z = 93 m/z = 65

  • CH 3 O - CO

Sulfides

ethyl isopropyl sulfide

S

MW = 104

M (104)

mz = 61 89 M- 75 M-

Amines

fragmentation patterns

α -cleavage ring formation NH 2

R NH

R +^2

n n

R N

R + N^

R"

H

H

R'

R"

R'

n = 1, m/z = 72 n = 2, m/z = 86 loss of H radical R N R N R' R" H R' R"

  • H M-

Amines

ethylamine

NH 2

MW = 45

M (45)

mz = 30 44 M- N H H H H base peak N H H H

Amines

triethylamine

N MW = 101 m/z = 30 N H H H H M (101) 100 M-

M-

α cleavage

Amines

N-ethylpropylamine

N

H

MW = 87

M (87)

m/z = 30 72 M-

M-

α cleavage

Mass Spectrometry: Fragmentation

Aromatic Amines

aniline

M (93)

M-

NH 2

MW = 93

NH

H H

-HCN

M-1 m/z = 66 m/z = 65

- H

m/z = 65

Carbonyl Compounds!!!!

α -cleavage (two possibilities)

β -cleavage

McLafferty rearrangement

Common Fragmentation Modes

R G

O

R C O + G

R G

O

R + G C O

G

O

R R^ +^

G

O

G = H, R', OH, OR', NR' 2

G O R H G O R H

Aliphatic Aldehydes

pentanal

H O MW = 86 M (86) mz = 29 85 M- mz = 43 mz = 44 McLafferty α cleavage H O H CH 3 CH 2 CH 2 H C O α cleavage C 4 H 9 C O β cleavage

Mass Spectrometry: Fragmentation

Aldehydes

2-ethylbutanal

M (100)

mz = 29 m/z = 72 H C O

H

O

MW = 100

H O H