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

Advanced Organic Chemistry: Mass spectrum of propanamide CH₃CH₂CONH₂

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

Interpreting the mass spectrum of propanamide (propionamide)

[Author © Dr Phil Brown PhD: Doc Brown's advanced level organic chemistry exam revision notes suitable for students of UK A level chemistry courses & US K12 grade 11, grade 12 and AP honors chemistry courses: Molecular spectroscopy analysis of propanamide [spectra page updated Mar 26th 2026 *]

Email doc brown re-edit mass spectrum of CH₃CH₂CONH₂

Links associated with propanamide * [privacy policy, cookies and disclaimer]

This is a BIG chemistry website, PLEASE take time to explore it

Mass spectrometry - spectra index

Introductory note on the mass spectrum of propanamide

Students and teachers please note my explanation of the mass spectrum of propanamide is designed for advanced, but pre-university, chemistry courses.

If M represents the propanamide molecule, the initial ionisation to give the molecular ion is:

M_(g) + high KE e^- ==> [M•]⁺_(g) + 2e^- and for fragmentation equations assume [M]⁺ is the start of the processes and all species are in a gaseous state.

I've not usually shown an unpaired electron on e.g. an ion or a non-ionised alkyl radical R e.g.

[M•]⁺ ==> [X]⁺ + R•, but you should be aware this is a more accurate depiction of some processes.

I've used simplified equations to show how some of the ions that might be formed in the fragmentation pattern for the mass spectrum of propanamide and only the formation of singly charged positive are considered for the mass spectrum of propanamide.

I've included a stick diagram and table of m/z ions for the mass spectrum of propanamide and doing the mass spectrum analysis under standard conditions, databases can be compiled based on complex fingerprint patterns, often involving the relative intensities of many fragment ions, and used to identify compounds including propanamide.

In selected cases, where two different fragment ions have the same integer m/z value, I've pointed out that modern mass spectrometers can measure relative ion mass to four decimal places. So, using accurate isotopic masses, I've calculated the accurate ion masses, BUT strictly speaking, 0.0005 should be deducted for singly charged ions to account for the loss of the electron in their formation. I have NOT done this for propanamide, but the mass spectrometer software does!

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

propanamide (propionamide), C₃H₇NO, , ,

The molecular structure and naming of carboxylic acids and derivatives
The classification, structure and naming of organic nitrogen compounds

Interpreting the fragmentation pattern of the mass spectrum of propanamide

[M]⁺ is the molecular ion peak (M) with an m/z of 73 corresponding to [C₃H₇NO]⁺, the original propanamide molecule minus an electron, [CH₃CH₂CONH₂]⁺

The small M+1 peak at m/z 74, corresponds to an ionised propanamide molecule with one ¹³C atom in it i.e. an ionised propanamide molecule of formula ¹³C¹²C₂H₇NO

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.

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

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

The base ion peak for the mass spectrum of propanamide is the m/z 44 ion [O=C-NH₂]⁺

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

Parent molecular ion for propanamide is the m/z 59 ion to [C₃H₇NO]⁺ or [CH₃CH₂CONH₂]⁺

m/z value of [fragment]⁺	72	57	55 ?	54	45	44
[molecular fragment]⁺	[C₃H₆NO]⁺	[CH₃CH₂C=O]⁺	[C₃H₃O]⁺ or [C₃H₅N]⁺	[C₃H₄N]⁺	[C₂H₅O]⁺ or [CH₃NO]⁺	[O=C-NH₂]⁺

m/z value of [fragment]⁺	30	29	28 [C₂H₄]⁺	27	26	18	15
[molecular fragment]⁺	CH₄N	[CH₃CH₂]⁺	[CH₂=CH₂]⁺	[C₂H₃]⁺	[C₂H₃]⁺	[?]⁺	[CH₃]⁺

Analysing and explaining the principal ions in the fragmentation pattern of the mass spectrum of propanamide (finger print pattern of ions and their abundances)

PLEASE NOTE I have found it difficult to find 'authentic' equations to explain mass spectra fragmentation patterns and it is complex chemistry! I've identified the formulae of the ionised fragments on the mass spectrum diagram, but the equations are from the internet or my conjecture as to how the ions might be formed - please take care in using the information, especially for assignments at university or pre-university level.

Possible suggested equations to explain the most abundant ion peaks of the propanamide mass spectrum

There are many fragments and lots of possible fragmentation process, some are more favoured than others, but this becomes university level analysis!

Formation of m/z 72 ion

[CH₃CH₂CONH₂]⁺ ===> [C₃H₆NO]⁺ + H

C-H or N-H bond scission in parent molecular ion, proton loss.

mass change 73 - 11 = 72 (M-16 ion peak)

Formation of m/z 57 ion

[CH₃CH₂CONH₂]⁺ ===> [CH₃CH₂C=O]⁺ + NH₂

C-N bond scission in parent molecular ion, loss of NH2 group

mass change 73 - 16 = 57 (M-16 ion peak)

Formation of m/z 55 ion

(i) [?]⁺ ===> [C₃H₃O]⁺ + ?

or more likely?

(ii) [?]⁺ ===> [C₃H₅N]⁺ + ?

I'm not sure which fragment species predominates for these pairs with the same m/z integer value, which I'm sure can be formed by other fragmentation reactions, BUT an accurate mass spectrometer can sort them out - can measure relative fragment ion masses to four decimal places e.g. using accurate relative isotopic masses:

¹H = 1.0078 ¹²C = 12.0000 ¹⁴N = 14.0031 ¹⁶O = 15.9949

Accurate relative ion masses: [C₃H₃O]⁺ = 55.0183 and [C₃H₅N]⁺ = 55.0421, difference of 0.0238 in ion relative mass can be easily resolved.

Formation of m/z 44 and 45 ions

[CH₃CH₂CONH₂]⁺ ===> [O=C-NH₂]⁺ + CH₃CH₂

C-C bond scission in the parent molecular ion, loss of ethyl group.

mass change = 73 - 29 = 44 (M-29 ion peak), [CH₂NO]⁺ (see below)

The m/z 44 ion is the base peak ion, the most abundant 'stable' ion fragment.

m/z 45 ion could be the related [¹³CH₂NO]⁺ formed in the same way or less likely the [C₂H₅O]⁺ ion.

Again, using accurate relative isotopic masses:

¹H = 1.0078 ¹²C = 12.0000 ¹³C = 13.0034 ¹⁴N = 14.0031 ¹⁶O = 15.9949: you can then calculate (predict) that the accurate relative ion masses are:

For m/z 45: [C₂H₅O]⁺ = 45.0339 and [¹³CH₂NO]⁺ = 45.0170, a relative ion mass difference of 0.01690 with C2H5O

Formation of m/z 26 to 29 ions

[CH₃CH₂CONH₂]⁺ ===> [CH₃CH₂]⁺ + CONH₂

C-C bond scission in the parent molecular ion, loss of CONH₂ group.

mass change = 73 - 44 = 29 (M-44 ion peak)

This m/z 29 ion can lose protons to generate the m/z 28, 27 and 26 ions.

The m/z 28 ion can be formed by elimination of ethene from a larger fragment of >= 2 carbon atoms and, similarly, the m/z 26 ion by the elimination of ethyne.

Formation of m/z 15 ion

[any of above m/z ions 29, 57, 72 or 73]⁺ ===> [CH₃]⁺ + neutral residue i.e. C-C bond scission of any ion with a CH₃ group.

Key words & phrases: how to interpret and explain the mass spectrum of propanamide m/z m/e base peaks, image and diagram of the mass spectrum of propanamide, details of the mass spectroscopy of propanamide, low and high resolution mass spectrum of propanamide, prominent m/z peaks in the mass spectrum of propanamide, comparative mass spectra of propanamide, the molecular ion peak in the mass spectrum of propanamide, analysing and understanding the fragmentation pattern of the mass spectrum of propanamide, characteristic pattern of peaks in the mass spectrum of propanamide, relative abundance of mass ion peaks in the mass spectrum of propanamide, revising the mass spectrum of propanamide, revision of mass spectroscopy of propanamide, most abundant ions in the mass spectrum of propanamide, how to construct the mass spectrum diagram for abundance of fragmentation ions in the mass spectrum of propanamide, how to analyse the mass spectrum of propanamide, how to describe explain the formation of fragmented ions in the mass spectra of propanamide equations for explaining the formation of the positive ions in the fragmentation of the ionised molecule of propanamide the mass spectrum of propionamide How do you interpret the mass spectrum of propanamide How to interpret the mass spectrum of propanamide Explanatory diagram of the mass spectrum of the propanamide molecule in terms of its molecular structure. Table listing data of the m/z ion prominent main peaks in the mass spectrum of propanamide. How to explain the mass spectrum of propanamide. The m/z value of the molecular ion peak in the mass spectrum of propanamide. Identifying propanamide from its mass spectrum pattern. The m/z m/e peak analysis interpretation diagram of the mass spectrum of the propanamide molecule. The uses of the mass spectrum of the propanamide molecule. The distinctive features of the mass spectrum of the propanamide molecule explained. explaining the fragmentation pattern of the mass spectrum of propanamide equations showing the formation of the ionised fragments in the mass spectrum of propanamide what does the mass spectrum tell you about the structure and properties of the propanamide molecule? Data table of ionised fragments in the mass spectrum of propanamide and equations for their formation in the fragmentation of the ionised propanamide molecule.

Links associated with propanamide

The infrared spectrum of propanamide

The H-1 NMR spectrum of propanamide (propionamide)

The C-13 NMR spectrum of propanamide (propionamide)

The chemistry of CARBOXYLIC ACIDS and DERIVATIVES revision notes INDEX

Mass spectrometry 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 revision notes, images, quizzes, worksheets etc. Copying of Doc Brown's pre-university advanced level chemistry website material is NOT permitted. Exam revision summaries & references to science course specifications are unofficial. These organic chemistry revision notes on spectroscopy (on the mass spectrum of propanal) are suitable for use of pre-university students studying AQA advanced level chemistry, Edexcel advanced level chemistry, OCR advanced level chemistry, IB advanced level chemistry, WJEC (Eduqas) advanced level chemistry, CIE advanced level chemistry, CCEA advanced level chemistry, US grade 11-12 AP honors chemistry courses and they will also prove useful to 1st year undergraduate students of chemistry.