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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

KNOCKHARDY PUBLISHINGKNOCKHARDY PUBLISHING

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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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