HOME PAGE * KS3 SCIENCES * GCSE BIOLOGY CHEMISTRY PHYSICS * ADVANCED LEVEL CHEMISTRY

SPECTROSCOPY INDEXES  *  All Advanced Organic Chemistry Notes  *  [SEARCH BOX]

Advanced Organic Chemistry: Mass spectrum of propanal

The mass spectrum of propanal (propionaldehyde)

Doc Brown's Chemistry Advanced Level Pre-University Chemistry Revision Study Notes for UK IB KS5 A/AS GCE advanced A level organic chemistry students US K12 grade 11 grade 12 organic chemistry courses involving molecular spectroscopy analysing mass spectra of propanal

mass spectrum of propanal fragmentation pattern of m/z m/e ions for analysis and identification of propionaldehyde image diagram doc brown's advanced organic chemistry revision notes 

propanal (propionaldehyde),  C3H6O, aldehydes and ketones nomenclature (c) doc b , aldehydes and ketones nomenclature (c) doc b , aldehydes and ketones nomenclature (c) doc b, aldehydes and ketones nomenclature (c) doc b

Interpreting the fragmentation pattern of the mass spectrum of propanal  (propionaldehyde)

[M]+ is the molecular ion peak (M) with an m/z of 58 corresponding to [C3H6O]+, the original propanal molecule minus an electron, [CH3CH2CHO]+.

The small M+1 peak at m/z 59, corresponds to an ionised propanal molecule with one 13C atom in it i.e. an ionised propanal molecule of formula 13C12C2H6O

Carbon-13 only accounts for ~1% of all carbon atoms (12C ~99%), but the more carbon atoms in the molecule, the greater the probability of observing this 13C M+1 peak.

Propanal has 3 carbon atoms, so on average, ~1 in 33 molecules will contain a 13C atom.

Identifying the species giving the most prominent peaks (apart from M) in the fragmentation pattern of propanal.

The parent molecular m/z 58 ion is [CH3CH2CHO]+

m/z value of [fragment]+ 57 39 31 30 29 29
[molecular fragment]+ [CH3CH2C=O]+ [C3H3]+ [H3CO]+ [H2C=O]+ [CHO]+ [CH3CH2]+
m/z value of [fragment]+ 28 28 27 26 18 15 14
[molecular fragment]+ [CO]+ [C2H4]+ [C2H3]+ [C2H2]+ [H2O]+ [CH3]+ [CH3]+

Analysing and explaining the principal ions in the fragmentation pattern of the mass spectrum of propanal

Atomic masses: H = 1; C = 12; O = 16; 

Bond enthalpies kJ/mol: C-C = 348;  C-H = 412;  C-O = 360; C=O = 743

Possible equations to explain some of the most abundant ion peaks of propanal

Formation of m/z 57 ion:

[CH3CH2CHO]+  ===>  [CH3CH2C=O]+  +  H

C-H bond scission in the parent molecular ion, mass change 58 - 1 = 57.

Elimination of water from this ion gives the m/z 39 ion of [C3H3]+, mass change 57 - 18 = 39.

Formation of m/z 29 ion:

(i) [CH3CH2CHO]+  ===>  [CHO]+  +  CH3CH2

(ii) [CH3CH2CHO]+  ===>  [CH3CH2]+  +  CHO

C-C bond fission of the parent molecular ion, mass change 58 - 29 = 29.

The m/z 29 ion is the base peak ion, the most abundant ion fragment from two sources, both formed from alternative ionisation of fragments from a C-C bond fission in the parent molecular ion of propanal.

Hydrogen atom loss from either gives the m/z 28 ion [C2H4]+  or  [CO]+.

Formation of m/z 15 ion:

Formed by C-C bond scission in the parent molecular ion or the m/z 29 ion.

[CH3CH2CHO]+  ===>  [CH3]+  +  C2H3O

[CH3CH2]+  ===>  [CH3]+  +  CH2


Key words & phrases: propionaldehyde image diagram on how to interpret and explain the mass spectrum of propanal m/z m/e base peaks, image and diagram of the mass spectrum of propanal, details of the mass spectroscopy of propanal,  low and high resolution mass spectrum of propanal, prominent m/z peaks in the mass spectrum of propanal, comparative mass spectra of propanal, the molecular ion peak in the mass spectrum of propanal, analysing and understanding the fragmentation pattern of the mass spectrum of propanal, characteristic pattern of peaks in the mass spectrum of propanal, relative abundance of mass ion peaks in the mass spectrum of propanal, revising the mass spectrum of propanal, revision of mass spectroscopy of propanal, most abundant ions in the mass spectrum of propanal, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of propanal, how to analyse the mass spectrum of propanal, how to describe explain the formation of fragmented ions in the mass spectra of propanal equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of propanal recognising the base ion peak of propanal propionaldehyde

Stick diagram of the relative abundance of ionised fragments in the fingerprint pattern of the mass spectrum of propanal. Table of the m/e m/z values and formula of the ionised fragments in the mass spectrum of propanal. The m/e m/z value of the molecular ion peak in the mass spectrum of propanal.  The m/e m/z value of the base ion peak in the mass spectrum of propanal. Possible examples of equations showing the formation of the ionised fragments in propanal. Revision notes on the mass spectrum of propanal. Matching and deducing the structure of the propanal molecule from its mass spectrum.


Links associated with propanal

The chemistry of ALDEHYDES and KETONES revision notes INDEX

The infrared spectrum of Propanal (propionaldehyde)

The H-1 NMR spectrum of Propanal (propionaldehyde)

The C-13 NMR spectrum of Propanal (propionaldehyde)

Mass spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com

TOP OF PAGE

 Doc Brown's Chemistry 

*

TOP OF PAGE