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OCR A Level Chemistry A – Module 4 Core Organic Chemistry

4.2.4
Analytical
Techniques

Section 4.2.4 covers infrared spectroscopy: bond vibrations, absorption by atmospheric gases and the link to global warming, identifying alcohols, aldehydes, ketones and carboxylic acids from their absorptions, monitoring air pollution and breathalysers; mass spectrometry: the molecular ion peak and fragmentation; and the deduction of structures from elemental analysis, mass spectra and infrared spectra together.

Exam Paper
Paper 2 & 3
H432/02 and H432/03
Specification Points
4.2.4 (a) – (h)
8 learning outcomes
Topic Parts
3 pages
Revision notes available
Exam Board
OCR A
H432 (2015 onwards)

Revision Notes

Work through 4.2.4 Analytical Techniques in a structured sequence.

m/z
Mass
Spectra
1
Available

Mass Spectra of Organic Compounds

Mass spectra of organic compounds: molecular ion, m/z, fragmentation patterns, common fragments, M+2 peaks for chlorine and bromine.

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Wavenumber / cm⁻¹
Infrared
Spectroscopy
2
Available

Infrared Spectroscopy

Infrared spectroscopy: bond vibrations, wavenumbers, characteristic absorptions of functional groups, broad O–H bands, the fingerprint region and identifying compounds.

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Evidence to structure
Identifying
Unknowns
3
Available

Identifying Unknown Compounds

Identifying unknown organic compounds: combining the molecular ion, fragmentation, infrared absorptions and chemical tests, with a worked example.

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Specification Coverage

4.2.4 Analytical Techniques – OCR A Level Chemistry A

The following OCR A learning outcomes state what candidates should be able to do. Wording is taken from the OCR A Level Chemistry A (H432) specification.

4.2.4 Analytical techniques

4.2.4(a)
infrared (IR) radiation causes covalent bonds to vibrate more and absorb energy
4.2.4(b)-i
absorption of infrared radiation by atmospheric gases containing C=O, O–H and C–H bonds (e.g. CO₂, H₂O and CH₄)
4.2.4(b)-ii
the suspected link between absorption of infrared radiation by atmospheric gases and global warming
4.2.4(b)-iii
the resulting changes to energy usage
4.2.4(c)(i)
use of an infrared spectrum of an organic compound to identify an alcohol from an absorption peak of the O–H bond
4.2.4(c)(ii)
use of an infrared spectrum of an organic compound to identify an aldehyde or ketone from an absorption peak of the C=O bond
4.2.4(c)(iii)
use of an infrared spectrum of an organic compound to identify a carboxylic acid from an absorption peak of the C=O bond and a broad absorption peak of the O–H bond
4.2.4(d)-i
interpretations of an infrared spectrum of familiar or unfamiliar substances using supplied data
4.2.4(d)-ii
predictions of an infrared spectrum of familiar or unfamiliar substances using supplied data
4.2.4(e)-i
use of infrared spectroscopy to monitor gases causing air pollution (e.g. CO and NO from car emissions)
4.2.4(e)-ii
use of infrared spectroscopy in modern breathalysers to measure ethanol in the breath
4.2.4(f)-i
use of a mass spectrum of an organic compound to identify the molecular ion peak
4.2.4(f)-ii
use of the molecular ion peak in a mass spectrum of an organic compound to determine molecular mass
4.2.4(g)
analysis of fragmentation peaks in a mass spectrum to identify parts of structures
4.2.4(h)(i)
deduction of the structures of organic compounds from different analytical data including elemental analysis (see also 2.1.3 c)
4.2.4(h)(ii)
deduction of the structures of organic compounds from different analytical data including mass spectra
4.2.4(h)(iii)
deduction of the structures of organic compounds from different analytical data including IR spectra