C3H8O CH3OCH2CH3 mass spectrum of methoxyethane fragmentation pattern of m/z m/e ions for analysis and identification of ethyl methyl ether image diagram doc brown's advanced organic chemistry revision notes

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 methoxyethane

Interpreting the mass spectrum of methoxyethane

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 methoxyethane

C3H8O CH3OCH2CH3 mass spectrum of methoxyethane fragmentation pattern of m/z m/e ions for analysis and identification of ethyl methyl ether image diagram doc brown's advanced organic chemistry revision notes

Methoxyethane

Interpreting the fragmentation pattern of the mass spectrum of methoxyethane

[M]⁺ is the molecular ion peak (M) with an m/z of 60 corresponding to [C₃H₈O]⁺, the original methoxyethane molecule minus an electron, [CH₃OCH₂CH₃]⁺.

The small M+1 peak at m/z 61, corresponds to an ionised methoxyethane molecule with one ¹³C atom in it i.e. an ionised methoxyethane molecule of formula [¹³C¹²C₂H₈O]⁺

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.

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

In the mass spectrum of ethers, an M+1 ion can also be formed by a hydrogen atom radical combining with the molecular ion i.e. m/z 61 can originate from [M]⁺ + H• ===> [•MH]⁺

The most abundant ion of the molecule under mass spectrometry investigation (methoxyethane) is usually given an arbitrary abundance value of 100, called the base ion peak, and all other abundances ('intensities') are measured against it.

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

Unless otherwise indicated, assume the carbon atoms in methoxyethane are the ¹²C isotope.

Some of the possible positive ions, [molecular fragment]⁺, formed in the mass spectrometry of methoxyethane.

m/z value of [fragment]⁺	59	45	43	31	29	28	27	15
[molecular fragment]⁺	[C₃H₇O]⁺	[C₂H₅O]⁺	[C₂H₃O]⁺	[CH₃O]⁺	[CH₃CH₂]⁺	[C₂H₄]⁺	[C₂H₃]⁺	[CH₃]⁺

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

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

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

Possible equations to explain the most abundant ion peaks of methoxyethane (tabulated above)

Formation of m/z 59 ion:

[CH₃OCH₂CH₃]⁺ ===> [C₃H₇O]⁺ + H

C-H bond scission and expulsion of a proton (mass change 60 - 1 = 59).

Formation of m/z 45 ion:

[CH₃OCH₂CH₃]⁺ ===> [C₂H₅O]⁺ + CH₃

Scission of a C-C or C-O bond to lose a methyl group from the parent molecular ion (see also m/z 15).

Mass change: 60 - 15 = 45

The m/z 45 ion is the base peak ion, the most abundant and 'stable' ion fragment.

The m/z ion may have the structure CH₃OCH₂ or OCH₂CH₃ or ?

Could also be formed from the m/z 59 ion?

[C₃H₇O]⁺ ===> [C₂H₅O]⁺ + CH₂

Formation of m/z 43 ion:

[C₃H₇O]⁺ ===> [C₂H₃O]⁺ + CH₄

Scission of a C-C or C-O bond to lose a methane from the m/z 59 ion ?

Mass change: 59 - 16 = 43

Formation of m/z 31 ion:

[CH₃OCH₂CH₃]⁺ ===> [CH₃O]⁺ + CH₂CH₃

C-O bond scission of the parent molecular ion (see also m/z 29 ion).

Mass change: 60 - 29 = 31

Formation of m/z 29 ion:

[CH₃OCH₂CH₃]⁺ ===> [CH₂CH₃]⁺ + CH₃O

C-O bond scission of the parent molecular ion.

Mass change: 60 - 31 = 29

Formation of m/z 15 ion:

[CH₃OCH₂CH₃]⁺ ===> [CH₃]⁺ + C₂H₅O

Scission of a C-C or C-O bond to lose a methyl group.

Mass change: 60 - 45 = 15

Key words & phrases: C3H8O CH3OCH2CH3 image diagram on how to interpret and explain the mass spectrum of methoxyethane m/z m/e base peaks, image and diagram of the mass spectrum of methoxyethane, details of the mass spectroscopy of methoxyethane, low and high resolution mass spectrum of methoxyethane, prominent m/z peaks in the mass spectrum of methoxyethane, comparative mass spectra of methoxyethane, the molecular ion peak in the mass spectrum of methoxyethane, analysing and understanding the fragmentation pattern of the mass spectrum of methoxyethane, characteristic pattern of peaks in the mass spectrum of methoxyethane, relative abundance of mass ion peaks in the mass spectrum of methoxyethane, revising the mass spectrum of methoxyethane, revision of mass spectroscopy of methoxyethane, most abundant ions in the mass spectrum of methoxyethane, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of methoxyethane, how to analyse the mass spectrum of methoxyethane, how to describe explain the formation of fragmented ions in the mass spectra of methoxyethane equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of methoxyethane recognising the base ion peak of methoxyethane interpreting interpretation the mass spectrum of methoxyethane for ethyl methyl ether spectrum of methoxyethane methyl ethyl ether CH3CH2OCH3

Links associated with methoxyethane

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