14-1 prepared by dr. khalid ahmad shadid islamic university in madinah department of chemistry ch-4...
TRANSCRIPT
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. -
14-9
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.
14-12
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"
+
14-17
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+
14-19
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
14-35
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