Organic Chemistry: A Guided Inquiry
2nd Edition
ISBN:9780618974122
Author:Andrei Straumanis
Publisher:Andrei Straumanis
ChapterL2: Mass Spectrometry
Section: Chapter Questions
Problem 27CTQ
Related questions
Question
Can you explain mass spectrometry? Can you explain how to fill it?
![F
1. Mass spectrometry measures mass of a compound.
2. Mass spectrometry also provides molecular formula and structural information.
3. A very small amount (non-recoverable) of a sample is vaporized in an ionization chamber. It is
then bombarded by high energy electrons.
4. A valenec electron from the sample is lost producing a RADICAL CATION (M).
5. The molecule may further breakdown in samll pieces (fragmentation i.e., cation fragments and
neutral fragments).
6. Cation fragments move through a pipe in a strong magnetic field and detected as lines by m/z
(mass to charge ratio). A detecter records the fragments as peaks.
MASS SPECTROMETRY [MS]
7. Tallest peak - 100% intensity = base peak.
8. Farthest - unfragmented cation = parent peak = corresponds to molecular ion(M).
9. There is often a small M+1 peak due to naturally occurring-isotopic abundance 13C (1.1%) and
²H (0.02%).
M-
M+1= CO₂ (1%), C₂H4O (2%)
M+2= usually very small, unless Cl, Br or S present.
35CI=75%, 37 CI=25%, M+2 intensity (~32%)
79Br=50%, 8¹Br-50%, M+2 intensity (~50%)
10. Compounds containing only C-12, H=1, 0-16 the molecular ion would be even number.
Compounds containing odd number of nitrogens would have molecular ion as odd number.
11. How smaller fragments are formed i.e. (M+; molecular ion) further breaks down. Information
provided in section 12.3. (Examples: alpha cleavage, dehydration, McLafferty
rearrangement).
a
M + 2e
(molecular ion,
a radical cation)
+ é
(e at 70 eV or 1600 kcal/mol,
resulting ions are very high in energy)
+
-lot
+2e
FRAGMENTATION!](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F637a8243-98d2-45ca-8dd1-4e9d7d0f97ca%2Fb22fe2af-5240-4baf-ac3e-4a41065689d4%2F5akatmo.jpeg&w=3840&q=75)
Transcribed Image Text:F
1. Mass spectrometry measures mass of a compound.
2. Mass spectrometry also provides molecular formula and structural information.
3. A very small amount (non-recoverable) of a sample is vaporized in an ionization chamber. It is
then bombarded by high energy electrons.
4. A valenec electron from the sample is lost producing a RADICAL CATION (M).
5. The molecule may further breakdown in samll pieces (fragmentation i.e., cation fragments and
neutral fragments).
6. Cation fragments move through a pipe in a strong magnetic field and detected as lines by m/z
(mass to charge ratio). A detecter records the fragments as peaks.
MASS SPECTROMETRY [MS]
7. Tallest peak - 100% intensity = base peak.
8. Farthest - unfragmented cation = parent peak = corresponds to molecular ion(M).
9. There is often a small M+1 peak due to naturally occurring-isotopic abundance 13C (1.1%) and
²H (0.02%).
M-
M+1= CO₂ (1%), C₂H4O (2%)
M+2= usually very small, unless Cl, Br or S present.
35CI=75%, 37 CI=25%, M+2 intensity (~32%)
79Br=50%, 8¹Br-50%, M+2 intensity (~50%)
10. Compounds containing only C-12, H=1, 0-16 the molecular ion would be even number.
Compounds containing odd number of nitrogens would have molecular ion as odd number.
11. How smaller fragments are formed i.e. (M+; molecular ion) further breaks down. Information
provided in section 12.3. (Examples: alpha cleavage, dehydration, McLafferty
rearrangement).
a
M + 2e
(molecular ion,
a radical cation)
+ é
(e at 70 eV or 1600 kcal/mol,
resulting ions are very high in energy)
+
-lot
+2e
FRAGMENTATION!
Transcribed Image Text:Relative Intensity
100
80
- 09
40
Soppenh
20-
lo
13
2.10
T
0 fmptır
10
20
t
30
CI
Chlorobenzene
mw 112.5
Metsindd
3
forbundankmahante
40 50
Landhanden frie en
www.
09
70
m/z-:
Ampan
80
ff
90
TTTT
b
100 110
1:
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