mass spectrum of propan-2-ol fragmentation pattern of m/z m/e ions for analysis and identification of 2-propanol image diagram doc brown's advanced organic chemistry revision notes

Advanced Organic Chemistry: Mass spectrum of propan-2-ol CH₃CH(OH)CH₃

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

The mass spectrum of propan-2-ol (2-propanol) CH₃CH(OH)CH₃ (re-edit)

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 propan-2-ol

Use your mobile phone in 'landscape' mode?

Mass spectroscopy - spectra index

Links associated with propan-2-ol

mass spectrum of propan-2-ol fragmentation pattern of m/z m/e ions for analysis and identification of 2-propanol image diagram doc brown's advanced organic chemistry revision notes

Propan-2-ol C₃H₈O, , , ,

Interpreting the fragmentation pattern of the mass spectrum of propan-2-ol (2-propanol, isopropyl alcohol)

[M]⁺ is the molecular ion peak (M) with an m/z of 60 corresponding to [C₃H₈O]⁺, the original propan-2-ol molecule minus an electron, [CH₃CH(OH)CH₃]⁺.

However, this is a highly unstable molecular ion, only a trace is detected.

The even smaller M+1 peak at m/z 61, corresponds to an ionised propan-2-ol molecule with one ¹³C atom in it i.e. an ionised propan-2-ol molecule of formula ¹³C¹²C₂H₈O

Identifying the species giving the most prominent peaks (apart from M) in the fragmentation pattern of propan-2-ol.

m/z value of [fragment]⁺	59	45	43 ?	43 ?	41
[molecular fragment]⁺	[CH₃CHOCH₃]⁺	[CH₃CHOH]⁺	[CH₃CO]⁺	[C₃H₇]⁺	[C₃H₅]⁺

m/z value of [fragment]⁺	39	31	29 ?	29	27	19	15
[molecular fragment]⁺	[C₃H₃]⁺	[CH₂OH]⁺	[CHO]⁺	[C₂H₅]⁺	[C₂H₃]⁺	[?]⁺	[CH₃]⁺

Analysing and explaining the principal ions in the fragmentation pattern of the mass spectrum of propan-2-ol

Examples of equations to explain some of the most abundant ion peaks of the mass spectrum of propan-2-ol

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

Bond enthalpies kJ/mol: C-C = 348; C-H = 412; C-O = 360; O-H = 463

Formation of m/z 59 ion:

[CH₃CH(OH)CH₃]⁺ ===> [CH₃CHOCH₃]⁺ + H

C-H bond scission and proton loss from parent molecular ion m/z 60 of propan-2-ol, mass change 60 - 1 = 59..

Formation of m/z 45 ion:

[CH₃CH(OH)CH₃]⁺ ===> [CH₃CHOH]⁺ + CH₃

C-C bond scission of the parent molecular ion, mass change 60 - 15 = 45.

The m/z 45 ion is the base peak, the most abundant stable ion fragment for propan-2-ol.

Formation of m/z 27 ion:

[CH₃CHOH]⁺ ===> [CH₃CHOH]⁺ + H₂O

Elimination of water from the m/z 45 ion, mass change 45 - 18 = 27.

Formation of m/z 15 ion:

[CH₃CH(OH)CH₃]⁺ ===> [CH₃]⁺ + CH₃CHOH

C-C bond scission of the parent molecular ion, mass change 60 - 45 = 15, but the m/z 45 ion is more likely to be formed from this fragmentation reaction.

Comparing the infrared, mass, 1H NMR and 13C NMR spectra of the 3 isomers of C₃H₈O NOTE: The images are linked to their original detailed spectral analysis pages AND can be doubled in size with touch screens to increase the definition to the original propan-1-ol, propan-2-ol and methoxyethane image sizes.

	I wasn't able to obtain an infrared spectrum for methoxyethane, so I've added the infrared spectrum of ethoxyethane to enable a few comparisons with two aliphatic alcohols Comparing the infrared spectra of propan-1-ol, propan-2-ol and methoxyethane Propan-1-ol, propan-2-ol and methoxyethane are structural isomers of molecular formula C₃H₈O Propan-1-ol, propan-2-ol and methoxyethane exemplify infrared spectra of the lower members of the homologous series of aliphatic alcohols and ethers
INFRARED SPECTRA (above): There are, as expected, differences in the fingerprint region at wavenumbers 1500 to 400 cm^-1, but most absorptions for all three molecules are the various C-O and the many C-H vibrational modes. However, there is one characteristic distinguishing absorption only present in the infrared spectra of alcohols, but not in ethers, that is the broad O-H stretching vibration peaking at ~3350 cm^-1. There is also another broad absorption band (origin?) peaking at ~650 cm^-1 in the alcohol spectra, but not in the ether spectra.

	Comparing the mass spectra of propan-1-ol, propan-2-ol and methoxyethane Propan-1-ol, propan-2-ol and methoxyethane are structural isomers of molecular formula C₃H₈O Propan-1-ol, propan-2-ol and methoxyethane exemplify the mass spectra of the lower members of the homologous series of aliphatic alcohols and ethers
MASS SPECTRA (above): The base ion peaks are m/z 45 for propan-2-ol and methoxyethane, but that of propan-1-ol is m/z 31. Many of the fragmentation ions are common to all three spectra. The m/z 45 ion is peak is much smaller in the propan-1-ol spectrum compared to the other two. The molecular ion peak height for propan-2-ol is relative small compared to the other two spectra suggesting it is much the less stable m/z 56 ion.

	Comparing the 1H proton NMR spectra of propan-1-ol, propan-2-ol and methoxyethane Propan-1-ol, propan-2-ol and methoxyethane are structural isomers of molecular formula C₃H₈O Propan-1-ol, propan-2-ol and methoxyethane exemplify the 1H proton NMR spectra of the lower members of the homologous series of aliphatic alcohols and ethers
1H NMR SPECTRA (above): The 1H NMR spectra of all three molecules give different integrated proton ratios for the different ¹H chemical environments i.e. the proton ratios are as follows: propan-1-ol 3:2:2:1; propan-2-ol 6:1:1 and methoxyethane 3:2:3. Therefore, all three can be distinguished by their ¹H NMR spectra.

	Comparing the carbon-13 NMR spectra of propan-1-ol, propan-2-ol and methoxyethane Propan-1-ol, propan-2-ol and methoxyethane are structural isomers of molecular formula C₃H₈O Propan-1-ol, propan-2-ol and methoxyethane exemplify the carbon-13 NMR spectra of members of the lower members of the homologous series of aliphatic alcohols and ethers
13C NMR SPECTRA (above): The ¹³C NMR spectra of propan-1-ol and methoxyethane show three different ¹³C NMR chemical shifts, but propan-2-ol can be distinguished from the other two by exhibiting only two chemical shift lines. You would need other spectral data to distinguish propan-1-ol and methoxyethane.

Key words & phrases: 2-propanol isopropyl alcohol image diagram on how to interpret and explain the mass spectrum of propan-2-ol m/z m/e base peaks, image and diagram of the mass spectrum of propan-2-ol, details of the mass spectroscopy of propan-2-ol, low and high resolution mass spectrum of propan-2-ol, prominent m/z peaks in the mass spectrum of propan-2-ol, comparative mass spectra of propan-2-ol, the molecular ion peak in the mass spectrum of propan-2-ol, analysing and understanding the fragmentation pattern of the mass spectrum of propan-2-ol, characteristic pattern of peaks in the mass spectrum of propan-2-ol, relative abundance of mass ion peaks in the mass spectrum of propan-2-ol, revising the mass spectrum of propan-2-ol, revision of mass spectroscopy of propan-2-ol, most abundant ions in the mass spectrum of propan-2-ol, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of propan-2-ol, how to analyse the mass spectrum of propan-2-ol, how to describe explain the formation of fragmented ions in the mass spectra of propan-2-ol equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of propan-2-ol recognising the base ion peak of propan-2-ol 2-propanol isopropyl alcohol isomer of molecular formula C3H8O Stick diagram of the relative abundance of ionised fragments in the fingerprint pattern of the mass spectrum of propan-2-ol. Table of the m/e m/z values and formula of the ionised fragments in the mass spectrum of propan-2-ol. The m/e m/z value of the molecular ion peak in the mass spectrum of propan-2-ol. The m/e m/z value of the base ion peak in the mass spectrum of propan-2-ol. Possible examples of equations showing the formation of the ionised fragments in propan-2-ol. Revision notes on the mass spectrum of propan-2-ol. Matching and deducing the structure of the propan-2-ol molecule from its mass spectrum. Mass spectroscopy of aliphatic alcohols, mass spectra of propan-2-ol, an isomer of molecular formula C3H8O 2-propanol Explanatory diagram of the mass spectrum of the propan-2-ol 2-propanol molecule in terms of its molecular structure. Listing data of the prominent main peaks in the mass spectrum of propan-2-ol 2-propanol. How to explain the mass spectrum of propan-2-ol 2-propanol. The m/z value of the molecular ion peak in the mass spectrum of propan-2-ol 2-propanol. Identifying propan-2-ol 2-propanol from its mass spectrum pattern. The m/z m/e peak analysis of the mass spectrum of the propan-2-ol 2-propanol molecule. The uses of the mass spectrum of the propan-2-ol 2-propanol molecule. The distinctive features of the mass spectrum of the propan-2-ol 2-propanol molecule explained. explaining the fragmentation pattern of the mass spectrum of propan-2-ol 2-propanol equations showing the formation of the ionised fragments in the mass spectrum of propan-2-ol 2-propanol what does the mass spectrum tell you about the structure and properties of the propan-2-ol 2-propanol molecule?

Links associated with propan-2-ol

The chemistry of ALCOHOLS revision notes INDEX

The infrared spectrum of Propan-2-ol (2-propanol, isopropyl alcohol)

The H-1 NMR spectrum of Propan-2-ol (2-propanol, isopropyl alcohol)

The C-13 NMR spectrum of Propan-2-ol (2-propanol, isopropyl alcohol)

Mass spectroscopy index

ALL SPECTROSCOPY INDEXES

All Advanced Organic Chemistry Notes

Use My Google search site box

Email doc b: chem55555@hotmail.com

Website content © Dr Phil Brown 2000+. All copyrights reserved on Doc Brown's advanced level pre-university organic chemistry revision notes, images, quizzes, worksheets etc. Copying of website material is NOT permitted. Exam revision summaries and references to science course specifications are unofficial. Please email if not happy about anything.