14-1

Prepared By

Dr. Khalid Ahmad Shadid

Islamic University in MadinahDepartment of Chemistry

CH-4 Part 2

Mass Spectroscopy

14-2

MASS SPECTROSCOPYالكتلة مطياف

عمليات - خالل من البنائية الصيغة على التعرفحطيمات المركب تفكك او التكسير

يتفكك- او يتكسر بالتالي ثابت غير الكاتيوني الجذرصغيرة حطيمات او ايونات الى

MHIGH ENERGY

70 eVM+ . + e-

FRAGMENTATION

UNKNOWNCOMPOUND

14-3

Molecules with Heteroatoms

Isotopes are present in their usual abundance. Carbon has a 13C isotope present in 1.1% abundance. The

spectrum will show the normal M+ and small M+1 peak. Bromine has two isotopes: 79Br (50.5%) and 81Br (49.5%).

Since the abundances are almost equal, there will be an M+ peak and and M+2 peak of equal height.

14-4

Mass Spectrum with Bromine

Bromine is a mixture of 50.5% 79Br and 49.5% 81Br. The molecular ion peak M+ has 79Br be as tall as the M+2 peak that has 81Br.

14-5

Mass Spectrum with Chlorine

Chlorine is a mixture of 75.5% 35Cl and 24.5% 37Cl. The molecular ion peak M+ is 3 times higher than the M+2 peak.

14-6

Mass Spectrum with Sulfur

Sulfur has three isotopes: 32S (95%), 33S (0.8%), and 34S (4.2%).

The M+ peak of ethyl methyl sulfide has an M+2 peak that is larger than usual (about 4% of M+).

14-7

Hexane (m/z = 86 for parent) has peaks at m/z = 71, 57, 43, 29

Alkanes --- Fragmentation of Hexane

CH3. - CH3CH2

. - CH3CH2CH2. -

14-8

Fragmentation of the Hexane Radical Cation

14-9

Mass Spectrum of n-Hexane

Groups of ions correspond to loss of one-, two-, three-, and four-carbon fragments.

14-10

Fragmentation of Branched Alkanes

• The most stable

carbocation

fragments form in greater

amounts.

14-11

Alkanes

Figure 14.6 Mass spectrum of 2,2,4-trimethylpentane.

14-12

Mass Spectra of AlkenesAlkenes characteristically:

Show a strong molecular ion peak.Cleave readily to form resonance-stabilized allylic cations.

14-13

Alkynes

Alkynes typically Show a strong molecular ion peak. Cleave readily to form the resonance-stabilized

propargyl cation or substituted propargyl cations.

Figure 14.9 Mass spectrum of 12-pentyne.

HC C=CH2HC C-CH2+ +3-Propynyl cation

(Propargyl cation)

14-14

Alcohols

One of the most common fragmentation patterns of alcohols is loss of H2O to give a peak which corresponds to M-18.

Another common pattern is loss of an alkyl group from the carbon bearing the OH to give a resonance-stabilized oxonium ion and an alkyl radical.

•

Molecular ion(a radical cation)

A radical

••

• ++O HC R

••

••

+R'-C O H

A resonance-stabilized oxonium ion

R

R"

R'

R"R'-C=O-H

R"

+

14-15

Alcohols

Figure 14.10 Mass spectrum of 1-butanol.

14-16

Mass Spectra of Alcohols

14-17

Aldehydes and Ketones

Characteristic fragmentation patterns are: cleavage of a bond to the carbonyl group (-cleavage). McLafferty rearrangement.

m/z 128

+•-cleavage

m/z 43+

•

+

+

m/z 113CH3

O

O

•

O

+

•+

m/z 58

McLaffertyrearrangement

Molecular ionm/z 114

•+O

HO

H+

14-18

Aldehydes and Ketones

Figure 14.11 Mass spectrum of 2-octanone.

14-19

Carboxylic Acids

Characteristic fragmentation patterns are -cleavage to give the ion [CO2H]+ with m/z 45.

McLafferty rearrangement.

-cleavage• +

m/z 45

O=C-O-HOH

O

Molecular ionm/z 88

+

•+•+

+

McLaffertyrearrangement

m/z 60

OH

OH

OH

OHMolecular ion

m/z 88

14-20

Carboxylic Acids

Figure 14.12 Mass spectrum of butanoic acid.

m/z 88 = molecular ion m/z 45 = [COOH]+

m/z 60 = McLafferty rearrangement product

14-21

Esters

-cleavage and McLafferty rearrangement

+

+

•+•+ m/z 71

m/z 59

Molecular ionm/z 102

-cleavage

OCH3

OCH3

O

O

OCH3

O+

m/z 74

McLaffertyrearrangement +

+•+•

O

OCH3

H OH

OCH3

Molecular ionm/z 102

14-22

Esters

Figure 14.13 Mass spectrum of methyl butanoate.

m/z 102 = molecular ion m/z 74 = McLafferty rearrangement m/z 71 and 59 = the result of cleavage

14-23

Aromatic Hydrocarbons

Most show an intense molecular ion peak. Most alkylbenzenes show a fragment ion of m/z 91.

Figure 14.14 Mass spectrum of toluene.

+•

+ Tropylium cation (m/z 91)

Toluene radical cation

CH3 H

HH

H

HH

H

-H•

14-24

Amines

Figure 14.15 Mass spectrum of 3-methyl-1-butanamine. The most characteristic fragmentation pattern of 1°, 2°, and 3° aliphatic amines is -cleavage.

m/z 30

++•

-cleavageCH3 CH3

CH3-CH-CH2-CH2-NH2 CH3-CH-CH2 CH2=NH2

14-25

Problem 14.31

2-Methylpentanal and 4-methyl-2-pentanone are constitutional isomers with the molecular formula C6H12O. Each shows a molecular ion in its mass spectrum at m/z 100. Spectrum A shows significant peaks at m/z 85, 58, 57, 43, and 42. Spectrum B shows significant peaks at m/z 71, 58, 57, 43, and 29. Assign each compound its correct spectrum.

14-26

Problem 14.31

The expected -cleavage and McLafferty rearrangement fragmentations are:

The -cleavage fragments at m/z 85 (Spectrum A) and 29 (Spectrum B) demonstrate that spectrum A corresponds to 4-methyl-2-pentanone, and Spectrum B corresponds to 2-methylpentanal.

14-27

MHIGH ENERGY

70 eVM+ .

UNKNOWNCOMPOUND

A+. + B

C+ + D.

E+ + C

التكسير قواعد

كاتيوني جذرمن فردي عدد

الاللكترونات

متعادل جزيئمن زوجي عدد

الاللكترونات

كاتيون

حر جذر

كاتيون

متعادل جزيئمن زوجي عدد

الاللكترونات

14-28

الكحوالت تكسير

m/z

0

100

Relative intensity

70

+

M+.

88

+ .

C5H10

C5H12O

55

+C4H7

+CH2OH

31

OH

Chemical Formula: C5H12Om/z: 88

14-29

الكحوالت تكسير

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

..

- e-

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

.H H

+

ماء جزيئ بفقد تمتاز الكحوالت

14-30

الكحوالت `تكسير

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

..

- e-

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

.H H

H3C

O..

H

.H

H

+

+

Chemical Formula: C5H12Om/z: 88

14-31

الكحوالت `تكسير

70

+C5H10

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

..

- e-

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

.H H

H3C

O..

H

.H

H

+

+

- H2O-18

Chemical Formula: C5H12Om/z: 88

H3C

H

.

+

14-32

الكحوالت `تكسير

70

+C5H10

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

..

- e-

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

.H H

H3C

O..

H

.H

H

+

+

- H2O-18

Chemical Formula: C5H12Om/z: 88

H3C

H

.

+

- CH3.

55

+C4H7

H

..

+

14-33

الكحوالت `تكسير

H3C

OH

Chemical Formula: C5H12Om/z: 88

..

.H H

+

.

FREE RADICAL

+ H OH..

. +

H

.

O

H

H

H

..

31

+

متماثل كسر

14-34

الكربوكسيلية االحماض تكسير

عند خط بوجود :تمتازm/z = 45

االيون ةنتيج وجود COOH+

14-35

الكربوكسيلية االحماض تكسير

R O

FREE RADICAL

O

H- 1e-

R O

O

H

..

.

+ .

homolytic cleavage

- R.

O

O

H

..

..

A

A

B

+ CO O

H

..+

m/z = 45

14-36

الكربوكسيلية االحماض تكسير

R O

FREE RADICAL

O

H- 1e-

R O

O

H

..

.

+ .

homolytic cleavage

- R.

O

O

H

..

..

A

A B

B

+ CO O

H

..+

m/z = 45

OH....

.

R

O

.. ..

+

R O..

+

m/z = M - 17

heterolytic cleavage

14-37

االلديهيدات تكسير

الجزيئي لاليون الضعيف بالظهور تمتازالفا كسر هو التكسير انواع اهم من

αهما ايونين ينتج حيث

M-R, M-1مع = المربوطة المجموعات كسر الفا كسر

C=O

14-38

R H

FREE RADICAL

O

- 1e-

R

O +.

homolytic cleavage

- R.

H

O

.

A

A B

B

H.

R

O

.. +

R O..

+

m/z = M - 1

.. .. .. .+

H

.. .

H O..

+

CHO+ m/z = 29

homolytic cleavage

.

.

االلديهيدات تكسير

14-39

R H

FREE RADICAL

O

- 1e-

R

O +.

homolytic cleavage

- R.

H

O

.

A

A B

B

H.

R

O..

+

R O..

+

m/z = M - 1

.. . . . . .+

H

...

H O..

+

CHO+ m/z = 29

homolytic cleavage

.

.

االلديهيدات تكسير

14-40

R H

FREE RADICAL

O

- 1e-

R

O +.

homolytic cleavage

- R.

H

O

.

A

A B

B

H.

R

O

.. +

R O..

+

m/z = M - 1

.. .. .. .+

H

.. .

H O..

+

CHO+ m/z = 29

homolytic cleavage

.

.

االلديهيدات تكسير

14-41

R H

FREE RADICAL

O

- 1e-

R

O +.

homolytic cleavage

- R.

H

O

.

A

A B

B

H.

R

O..

+

R O..

+

m/z = M - 1

.. . . . . .+

H

...

H O..

+

CHO+ m/z = 29

homolytic cleavage

.

.

االلديهيدات تكسير

14-42

R H

FREE RADICAL

O

- 1e-

R

O +.

homolytic cleavage

- R.

H

O

.

A

A B

B

H.

R

O..

+

R O..

+

m/z = M - 1

.. . . . . .+

H

...

H O..

+

CHO+ m/z = 29

homolytic cleavage

.

.

االلديهيدات تكسير

14-43

الكيتونات تكسير

الفا كسر هو التكسير انواع اهم منα

مع = المربوطة المجموعات كسر الفا كسرC=O

ينتج هما 4حيث ايونات :

14-44

O

- 1e-

. . . .

H3C

CH312

34

56

O.. .

H3C

CH312

34

56

break C2-C3

CH3CH2 +m/z = 29

+O. ..

CH33

4

56..

and

CH3CH3.

+

O. . .

CH33

4

56.

+

m/z = 71

O ..

CH33

4

56

+

m/z = 71

+

break C3-C4

O.. .

H3CCH31

23

4

56..

+

m/z = 43

and

O. . .

H3C CH31

23 4

56

..

m/z = 57

الكيتونات تكسير

14-45

O

- 1e-

.. ..

H3C

CH312

34

56

O

.. .

H3C

CH312

34

56

break C2-C3

CH3CH2 +m/z = 29

+O

. ..

CH33

4

56..

and

CH3CH2

.

+

O

. ..

CH33

4

56.

+

m/z = 71

O

..

CH33

4

56

+

m/z = 71

+

break C3-C4

O

.. .

H3CCH31

23

4

56..

+

m/z = 43

and

O

.. .

H3C CH31

23 4

56

..

m/z = 57

الكيتونات تكسير

14-46

O

- 1e-

. . . .

H3C

CH312

34

56

O.. .

H3C

CH312

34

56

break C2-C3

CH3CH2 +m/z = 29

+O. ..

CH33

4

56..

and

CH3CH3.

+

O. . .

CH33

4

56.

+

m/z = 71

O ..

CH33

4

56

+

m/z = 71

+

break C3-C4

O.. .

H3CCH31

23

4

56..

+

m/z = 43

and

O. . .

H3C CH31

23 4

56

..

m/z = 57

الكيتونات تكسير

14-47

O

- 1e-

.. ..

H3C

CH312

34

56

O

.. .

H3C

CH312

34

56

break C2-C3

CH3CH2 +m/z = 29

+O

. ..

CH33

4

56..

and

CH3CH3.

+

O

. ..

CH33

4

56.

+

m/z = 71

O

..

CH33

4

56

+

m/z = 71

+

break C3-C4

O

.. .

H3CCH31

23

4

56..

+

m/z = 43

and

O

.. .

H3C CH31

23 4

56

..

m/z = 57

+

الكيتونات تكسير

14-48

الكيتونات تكسير

m/z

0

100

Relative intensity

71

M+.

1005729

O

Chemical Formula: C6H12Om/z: 100

43

14-49

االسترات تكسير

الفا كسر هو التكسير انواع اهم منα

مع = المربوطة المجموعات كسر الفا كسرC=O

ينتج هما 4حيث ايونات :

14-50

R1 O

O

.. .

R2

R1+

O

O

. .

R2

+

R1.

_

+- COOR2

- R1CO.

OR2+

- R2O.

R1

O

..

+

Acylium ion

.

االسترات تكسير

14-51

R1 O

O

.. .

R2

R1+

O

O

. .

R2

+

R1.

_

+- COOR2

- R1CO.

OR2+

- R2O.

R1

O

..

+

Acylium ion

.

االسترات تكسير

14-52

R1 O

O

.. .

R2

R1+

O

O

. .

R2

+

R1.

_

+- COOR2

- R1CO.

OR2+

- R2O.

R1

O

..

+

Acylium ion

.

االسترات تكسير

14-53

R1 O

O

.. .

R2

R1+

O

O

. .

R2

+

R1.

_

+- COOR2

- R1CO.

OR2+

- R2O.

R1

O

..

+

Acylium ion

.

االسترات تكسير

14-54

االثرات تكسير

بيتا كسر هو التكسير انواع اهم منβ

الـــ = رابطة كسر بيتا كسرC-C

مع المربوطةC-Oالــــ

14-55

االثرات تكسير

R-CH2-O-R..

.. - 1 e-R-CH2-O-R

.

..

+CH3-O-R

.

..+. + R.

O

H

H R

..+

if R= CH3, m/z=45if R= CH2CH3, m/z=59if R= CH2CH2CH3, m/z=73

14-56

االثرات تكسير

R-CH2-O-R..

.. - 1 e-R-CH2-O-R

.

..

+CH2-O-R

.

..+. + R.

O

H

H R

..+

if R= CH3, m/z=45if R= CH2CH3, m/z=59if R= CH2CH2CH3, m/z=73

14-57

االثرات تكسير

R-CH2-O-R..

.. - 1 e-R-CH2-O-R

.

..

+CH2-O-R

.

..+. + R.

O

H

H R

..+

if R= CH3, m/z=45if R= CH2CH3, m/z=59if R= CH2CH2CH3, m/z=73

14-58

االثرات تكسير

R-CH2-O-R..

.. - 1 e-R-CH2-O-R

.

..

+CH2-O-R

.

..+. + R.

O

H

H R

..+

if R= CH3, m/z=45if R= CH2CH3, m/z=59if R= CH2CH2CH3, m/z=73

14-59

االثرات تكسير

خطوط على نحصل الكسر لهذا ونتيجة45و 59و 73عند

R-CH2-O-R..

.. - 1 e-R-CH2-O-R

.

..

+CH2-O-R

.

..+. + R.

O

H

H R

..+

if R= CH3, m/z=45if R= CH2CH3, m/z=59if R= CH2CH2CH3, m/z=73

14-60

GOOD LUCK