Advanced Organic Chemistry: Mass spectrum of E-pent-2-ene and Z-pent-2-ene

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The mass spectrum of E-pent-2-ene and Z-pent-2-ene

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 E-pent-2-ene and Z-pent-2-ene (comparing the mass spectra of cis/trans isomers of 2-pentene)

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Mass spectroscopy - spectra index

C5H10 mass spectrum of E-pent-2-ene 2-pentene fragmentation pattern of m/z m/e ions for analysis and identification of trans-pent-2-ene image diagram doc brown's advanced organic chemistry revision notes 

The mass spectrum of the stereoisomer E-pent-2-ene (trans-2-pentene)

 

C5H10 mass spectrum of 2-pentene Z-pent-2-ene fragmentation pattern of m/z m/e ions for analysis and identification of cis-pent-2-ene image diagram doc brown's advanced organic chemistry revision notes

The mass spectrum of the stereoisomer Z-pent-2-ene (cis-2-pentene)

 

Pent-2-ene C5H10, alkenes structure and naming (c) doc b has two E/Z isomers E-pent-2-ene and Z-pent-2-ene

Z/cis- alkenes structure and naming (c) doc b , E/trans- alkenes structure and naming (c) doc b

Interpreting the fragmentation pattern of the mass spectrum of E-pent-2-ene and Z-pent-2-ene

The fragmentation patterns are quite similar so the following notes apply to both spectra.

[M]+ is the molecular ion peak with an m/z of 70 corresponding to [C5H10]+, the original E-pent-2-ene and Z-pent-2-ene molecule minus an electron, [CH3CH2CH=CHCH3]+.

The small M+1 peak at m/z 71, corresponds to an ionised E-pent-2-ene and Z-pent-2-ene molecule with one 13C atom in it i.e. an ionised E-pent-2-ene and Z-pent-2-ene molecule of formula 13C12C4H10

Identifying the species giving the most prominent peaks (apart from M) in the fragmentation pattern of E-pent-2-ene and Z-pent-2-ene.

m/z value of [fragment]+ 56 55 55 53
[molecular fragment]+ [C4H8]+ [CH2CH=CHCH3]+ [CH3CH2CH=CH]+ [C4H5]+
m/z value of [fragment]+ 42 41 39 29 27 39 29 27
[molecular fragment]+ [C3H6]+ [C3H5]+ [C3H3]+ [CH3CH2]+ [C2H3]+ [C3H3]+ [CH3CH2]+ [C2H3]+

Analysing and explaining the principal ions in the fragmentation pattern of the mass spectrum of E-pent-2-ene and Z-pent-2-ene

Equations to explain the most abundant ion peaks of E-pent-2-ene and Z-pent-2-ene

Formation of m/z 55 ion:

[CH3CH2CH=CHCH3]+  ===>  [CH3CH2CH=CH]+  +  CH3

via C-C bond chain scission, similarly ...

[CH3CH2CH=CHCH3]+  ===>  [CH2CH=CHCH3]+  +  CH3

The m/z 55 ion is the base peak ion, the most abundant and 'stable' ion fragment.

Formation of m/z 29 ion: [CH3CH2CH=CHCH3]+  ===>  [CH3CH2]+  +  CH=CHCH3]


Key words & phrases:C5H10 image diagram on how to interpret and explain the mass spectrum of E-pent-2-ene and Z-pent-2-ene m/z m/e base peaks, image and diagram of the mass spectrum of E-pent-2-ene and Z-pent-2-ene, details of the mass spectroscopy of E-pent-2-ene and Z-pent-2-ene,  low and high resolution mass spectrum of E-pent-2-ene and Z-pent-2-ene, prominent m/z peaks in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, comparative mass spectra of E-pent-2-ene and Z-pent-2-ene, the molecular ion peak in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, analysing and understanding the fragmentation pattern of the mass spectrum of E-pent-2-ene and Z-pent-2-ene, characteristic pattern of peaks in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, relative abundance of mass ion peaks in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, revising the mass spectrum of E-pent-2-ene and Z-pent-2-ene, revision of mass spectroscopy of E-pent-2-ene and Z-pent-2-ene, most abundant ions in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of E-pent-2-ene and Z-pent-2-ene, how to analyse the mass spectrum of E-pent-2-ene and Z-pent-2-ene, how to describe explain the formation of fragmented ions in the mass spectra of E-pent-2-ene and Z-pent-2-ene equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of E-pent-2-ene and Z-pent-2-ene recognising the base ion peak of E-pent-2-ene and Z-pent-2-ene interpreting interpretation the mass spectrum of E-pent-2-ene and Z-pent-2-ene mass spectra of the E/Z isomers of pent-2-ene cis/trans stereoisomers of 2-pentene mass spectra of cis pent-2-ene trans pent-2-ene cis 2-pentene trans 2-pentene C5H10


Links associated with E-pent-2-ene and Z-pent-2-ene

The chemistry of ALKENES revision notes INDEX

Mass spectroscopy index

The infrared spectra of the E/Z isomers of pent-2-ene (cis/trans isomers of 2-pentene)

The H-1 NMR spectra of the E/Z isomers of pent-2-ene (cis/trans isomers of 2-pentene)

The C-13 NMR spectra of the E/Z isomers of pent-2-ene (cis/trans isomers of 2-pentene)

ALL SPECTROSCOPY INDEXES

STEREOISOMERISM general definition, E/Z (geometric/geometrical cis/trans) isomerism

All Advanced Organic Chemistry Notes

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