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URTHER MASS
URTHER MASS
SPECTROMETRPECTROMETR
Y
A guide for A level studentsA guide for A level students
KNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING
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INTRODUCTION
This Powerpointshow is one of several produced to help students understand
selected topics at AS and A2 level Chemistry. It is based on the requirements of
the AQA and OC specifications but is suitable for other e!amination boards.
Individual students may use the material at home for revision purposes or it may
be used for classroom teachin" if an interactive white board is available.
Accompanyin" notes on this# and the full ran"e of AS and A2 topics# are available
from the $%OC$&A'( SCI)%C) *)+SIT) at...
www.argonet.co.uk/users/hoptonj/sci.htm
%avi"ationis achieved by...
either clic,in" on the "rey arrows at the foot of each pa"e
or usin" the left and ri"ht arrow ,eys on the ,eyboard
MASS SPECTROMETRYMASS SPECTROMETRY
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$efore you start it %oul" &e helpful to'
- recall the &asic principles of a mass spectrometer
- !no% the "ifferent types of functional group in organic chemsitry
MASS SPECTROMETRYMASS SPECTROMETRY
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IONIS(TION
FR()ENTION
FR()ENTIONRE-(RR(N)EENT
O*ECU*(R (SS DETERIN(TIONO*ECU*(R (SS DETERIN(TION
USIN) (SS S+ECTROETR,USIN) (SS S+ECTROETR,
No%a"ays mass spectrometry is use"to i"entify un!no%n or ne% compoun"s.
When a molecule is ionise" it forms a
O*ECU*(R ION%hich can also
un"ergo FR()ENT(TIONor RE-
(RR(N)EENTto pro"uce particles of
smaller mass.
Only particles %ith a positi/e charge
%ill &e "eflecte" an" "etecte".
The resulting spectrum has many pea!s.
The final pea! 012sho%s the molecular
ion0highest m34 /alue2 an" in"icates the
molecular mass. The rest of the
spectrum pro/i"es information a&out
the structure.
O*ECU*(R ION
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Spectra o&taine" for organic molecules ha/e many pea!s. Each pea! is "ue to a
particular fragment %ith a certain m34 /alue.
highest m34 /alue usually correspon"s to the molecular ion
its position pro/i"es information a&out the molecular mass of a su&stance
the tallest pea!s come from the most sta&le species
T5E (SS S+ECTRUT5E (SS S+ECTRU
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Spectra o&taine" for organic molecules ha/e many pea!s. Each pea! is "ue to a
particular fragment %ith a certain m34 /alue.
highest m34 /alue usually correspon"s to the molecular ion
its position pro/i"es information a&out the molecular mass of a su&stance
the tallest pea!s come from the most sta&le species
T5E (SS S+ECTRUT5E (SS S+ECTRU
Interpretation of thousan"s of spectra has sho%n that many classes of organic
compoun" sho% characteristic fragmentation patterns "ue to their functional groups.
It is possi&le to i"entify the type of compoun" from its spectrum &y loo!ing at the ...
position of pea!s
"ifferences &et%een ma6or pea!s
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In the spectrum of octane a signal occurs at 778 "ue to the species C 95791
T5E (SS S+ECTRU -T5E (SS S+ECTRU - T5E O*ECU*(R IONT5E O*ECU*(R ION
7: ;: : ?: 9: @: 7:: 77: 7;: 7:
9:
7::
(&un"anceA
778
.
The species "ue to the final signalis !no%n as the molecular ionan" is usuallycorrespon"s to the molecular mass of the compoun".
molecular ion
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T5E (SS S+ECTRU -T5E (SS S+ECTRU - T5E O*ECU*(R IONT5E O*ECU*(R ION
The small pea! 0172 at 77= "ue to the natural a&un"ance 0a&out 7A2 of car&on-7
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T5E (SS S+ECTRU -T5E (SS S+ECTRU - FR()ENT(TIONFR()ENT(TION
7: ;: : ?: 9: @: 7:: 77: 7;: 7:
9:
7::
(&un"anceA
;@?7
85=COC5
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=?
8
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8