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Organic analysis
This topic introduces analytical evidence for functional groups and molecular structure.
7
Objectives
35
Flashcards
35
Questions
90 min
Study time
AQAA LevelChemistryOrganic chemistry
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Syllabus checklist
What you need to know
7 objective pages available
Test-tube reactions and mass spectrometry4 objectives
- Use test-tube reactions to identify alcohols, aldehydes, alkenes and carboxylic acids.
- Interpret mass spectra to identify molecular ion peaks.
- Use fragmentation evidence to support structural identification.
- Required practical: tests for alcohol, aldehyde, alkene and carboxylic acid.
Infrared spectroscopy3 objectives
- Use infrared absorption data to identify functional groups.
- Interpret the fingerprint region by comparison with reference spectra.
- Explain how infrared spectroscopy can monitor gases such as CO2, CH4 and H2O.
Key terms
test-tube reactionsmolecular ion peakfragmentation patternfragmentationmass spectrometryinfrared absorptionfunctional group identificationfingerprint regionreference spectraInfrared SpectroscopyMolecular Ion Peak
Exam tips
- Identifying Functional Groups: Perform a test-tube reaction with the appropriate reagent to identify the functional group present in the organic compound.
- Understanding Molecular Ion Peaks: When interpreting mass spectra, focus on identifying the molecular ion peak, which corresponds to the molecular weight of the compound.
Common mistakes
- Identifying Functional Groups: To correctly identify functional groups, remember that alcohols react with acidified potassium dichromate to produce a color change from orange to green, while aldehydes also react but may produce a different observable change when tested with Tollens' reagent, forming a silver mirror.
- Misidentifying Molecular Ion Peaks: To correctly identify the molecular ion peak, students should look for the highest m/z value that corresponds to the intact molecule. This peak represents the molecular weight of the compound and is crucial for determining the molecular formula.
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