Advanced Organic Chemistry: Infrared spectrum of butanoic acid CH3CH2CH2COOH

Interpreting and explaining the infrared spectrum of butanoic acid (butyric acid)

[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 spectrometry - analysing the infrared spectra of butanoic acid [spectra page updated April 3rd 2026 *]

 email doc brown Re-edit infrared spectrum of CH3CH2CH2COOH

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

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

 Infrared spectroscopy - spectra index

Introductory note on the infrared spectrum of butanoic acid

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

Based in the infrared spectrum diagram for butanoic acid, only some of the most prominent peaks for particular bond vibrations are discussed, particularly if butanoic acid has a functional group with a particular characteristic wavenumber peak.

The infrared spectrum of butanoic acid is unique and the whole, or selected wavenumbers, can be used to fingerprint its identity, sometimes analysing a mixture containing butanoic acid or following its change of concentration in a reaction.

infrared spectrum of butanoic acid C4H8O2 CH3CH2CH2COOH wavenumbers cm-1 functional group detection fingerprint pattern identification of butyric acid doc brown's advanced organic chemistry revision notes

Spectra obtained from a liquid film of butanoic acid. The right-hand part of the of the infrared spectrum of butanoic acid, wavenumbers ~1500 to 400 cm-1 is considered the fingerprint region for the identification of butanoic acid and most organic compounds. It is due to a unique set of complex overlapping vibrations of the atoms of the molecule of butanoic acid.

Butanoic acid (butyric acid)  (c) doc b  (c) doc b  (c) doc b

a carboxylic acid, see The molecular structure and naming of carboxylic acids and derivatives

Interpretation of the infrared spectrum of butanoic acid

The most prominent infrared absorption lines of butanoic acid

The hydroxyl O-H stretching vibration absorptions occur at wavenumbers 3300 to 2500 cm-1.

This is a broad series of bands due to interference from intermolecular hydrogen bonding between butanoic acid molecules - characteristic behaviour of carboxylic acids and any other molecule with a hydroxyl group.

One example of a hydrogen bond Oδ--Hδ+ǁǁǁ:Oδ- between butanoic acid molecules.

The O-H stretching vibrations overlap with C-H stretching vibrations, typically for alkyl groups at wavenumbers 2975 to 2845 cm-1 (so take care when looking for the presence of a hydroxyl group in a molecule).

The  C=O stretching vibration absorptions occur at wavenumbers 1725 to 1700 cm-1, characteristic of any molecule with a carbonyl group.

Although not unique, detection of these two groups in an infrared spectrum is indicative, but not proof, the molecule is a carboxylic acid e.g. the molecule could be a hydroxy-ketone!

The absence of other specific functional group bands will show that a particular functional group is absent from the butanoic acid molecular structure.

Key words & phrases: C4H8O2 CH3CH2CH2COOH image and diagram explaining the infrared spectrum of butanoic acid, complete infrared absorption spectrum of butanoic acid, comparative spectra of butanoic acid, prominent peaks/troughs for identifying functional groups in the infrared spectrum of butanoic acid, important wavenumber values in cm-1 for peaks/troughs in the infrared spectrum of butanoic acid, revision of infrared spectroscopy of butanoic acid, fingerprint region analysis of butanoic acid, how to identify butanoic acid from its infrared spectrum, identifying organic compounds like butanoic acid from their infrared spectrum, how to analyse the absorption bands in the infrared spectrum of butanoic acid detection of carboxylic acid functional groups in the butanoic acid molecule example of the infrared spectrum of a molecule like butanoic acid with a carboxylic acid functional group  interpreting interpretation of the infrared spectrum of butanoic acid shows presence of carboxylic acid functional group formula type functional group butyric acid C4H8O2 CH3CH2CH2COOH How do you interpret the infrared absorption spectrum of butanoic acid How to interpret the infrared spectrum of butanoic acid Explanatory diagram of the infrared spectrum of the butanoic acid molecule in terms of its molecular structure. Listing data of the prominent main wavenumber peaks troughs in the infrared spectrum of butanoic acid. How to explain the infrared spectrum of butanoic acid. Use of the infrared spectrum of butanoic acid, identification of butanoic acid from its infrared spectrum - fingerprint wavenumber pattern to identify the butanoic acid molecule. The uses of the infrared spectrum of the butanoic acid molecule. The distinctive features of the infrared spectrum of the butanoic acid molecule explained interpretation diagram explaining the peaks-trough of the transmittance of the infrared spectrum of butanoic acid what does the infrared spectrum tell you about the structure and properties of the butanoic acid molecule? How is infrared spectrum of butanoic acid used to identify butanoic acid?

Links associated with butanoic acid

The chemistry of CARBOXYLIC ACIDS and DERIVATIVES revision notes INDEX

The mass spectrum of butanoic acid

The H-1 proton NMR spectrum of butanoic acid

The 13C carbon-13 NMR spectrum of butanoic acid

Infrared 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 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 (infrared spectra of butanoic acid) 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.

TOP OF PAGE