mass spectrum of iodoethane C2H5I CH3CH2I fragmentation pattern of m/z m/e ions for analysis and identification of ethyl iodide image diagram doc brown's advanced organic chemistry revision notes

Advanced Organic Chemistry: Mass spectrum of iodoethane

SITEMAP * HOME PAGE * SEARCH * GCSE Level Chemistry age ~14-16 * Advanced Level Chemistry age ~16-19

Interpreting the mass spectrum of iodoethane (ethyl iodide)

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 iodoethane

email doc brown

Use your mobile phone or ipad etc. in 'landscape' mode

This is a BIG website, you need to take time to explore it

Mass spectroscopy - spectra index

mass spectrum of iodoethane C2H5I CH3CH2I fragmentation pattern of m/z m/e ions for analysis and identification of ethyl iodide image diagram doc brown's advanced organic chemistry revision notes

iodoethane, C₂H₅I, CH₃CH₂I, CH₃-CH₂-I

Interpreting the fragmentation pattern of the mass spectrum of iodoethane

[M]⁺ is the parent molecular ion peak (M) with an m/z of 156 corresponding to [C₂H₅I]⁺, the original iodoethane molecule minus an electron, [CH₃CH₂I]⁺.

The small M+1 peak at m/z 157, corresponds to an ionised iodoethane molecule with one ¹³C atom in it i.e. an ionised iodoethane molecule of formula [¹³C¹²CH₅I]⁺

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.

Iodoethane has 2 carbon atoms, so on average, ~1 in 50 molecules will contain a ¹³C atom.

The most abundant ion of the molecule under mass spectrometry investigation (iodoethane) 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 iodoethane.

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

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

The parent molecular ion of iodoethane m/z 156: [CH₃CH₂I]⁺, it is also the base peak ion too.

m/z value of [fragment]⁺	156	141	128	127	30	29	28	27	26	15
[molecular fragment]⁺	[C₂H₅I]⁺	[CH₂I]⁺	[HI]⁺	[I]⁺	[¹³C¹²CH₅]⁺	[C₂H₅]⁺	[C₂H₄]⁺	[C₂H₃]⁺	[C₂H₂]⁺	[CH₃]⁺

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

Atomic masses: H = 1; C = 12; I = 127

Bond enthalpies = kJ/mol: C-C = 348; C-H = 412; C-I = 238

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

Formation of m/z 141 ion:

[CH₃CH₂I]⁺ ===> [CH₂I]⁺ + CH₃

C-C bond scission in the parent molecular ion, mass change 156 - 15 = 141.

A much lower probability ionisation process than that forming the m/z ion 127 from the scission of the much weak C-I bond (see below).

Formation of m/z 127 ion:

[CH₃CH₂I]⁺ ===> [I]⁺ + C₂H₅

C-I bond scission in the parent molecular ion, mass change 156 - 29 = 127, an ionised iodine atom.

Formation of m/z 128 ion:

[CH₃CH₂I]⁺ ===> [HI]⁺ + C₂H₄

Elimination of hydrogen iodide from the parent molecular ion, mass change 156 - 28 = 128.

Formation of m/z 29 ion:

[CH₃CH₂I]⁺ ===> [C₂H₅]⁺ + C₂H₅I

C-I bond scission in the parent molecular ion, mass change 156 - 29 = 127.

The m/z 30 ion is most likely to be [C₂H₅]⁺ too, but containing a ¹³C atom.

Formation of m/z 28 ion:

[CH₃CH₂I]⁺ ===> [C₂H₄]⁺ + HI

Again, elimination of hydrogen iodide from the parent molecular ion, but this time the hydrocarbon fragment is ionised.

The m/z 28 ion can also be formed by hydrogen atom loss from the m/z 29 ion, and also hydrogen loss for either of these ions gives rise to m/z ions 27 and 26.

Key words & phrases: C2H5I CH3CH2I image diagram on how to interpret and explain the mass spectrum of iodoethane m/z m/e base peaks, image and diagram of the mass spectrum of iodoethane, details of the mass spectroscopy of iodoethane, low and high resolution mass spectrum of iodoethane, prominent m/z peaks in the mass spectrum of iodoethane, comparative mass spectra of iodoethane, the molecular ion peak in the mass spectrum of iodoethane, analysing and understanding the fragmentation pattern of the mass spectrum of iodoethane, characteristic pattern of peaks in the mass spectrum of iodoethane, relative abundance of mass ion peaks in the mass spectrum of iodoethane, revising the mass spectrum of iodoethane, revision of mass spectroscopy of iodoethane, most abundant ions in the mass spectrum of iodoethane, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of iodoethane, how to analyse the mass spectrum of iodoethane, how to describe explain the formation of fragmented ions in the mass spectra of iodoethane equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of iodoethane recognising the base ion peak of iodoethane interpreting interpretation the mass spectrum of iodoethane haloalkane halogenoalkane alkyl halide ethyl iodide functional group

Links associated with iodoethane

The chemistry of HALOGENOALKANES (haloalkanes) revision notes INDEX

The infrared spectrum of iodoethane (ethyl iodide)

The H-1 NMR spectrum of iodoethane (ethyl iodide)

The C-13 NMR spectrum of iodoethane (ethyl iodide)

Mass spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com