37. Analytical techniques
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37.1 Thin-layer chromatography
37.1.1And understand the terms
• Describe and understand the terms: (a) stationary phase, e.g. aluminium oxide (on a solid support); (b) mobile phase; a polar or non-polar solvent; (c) Rf value; (d) solvent front and baseline
37.1.2Rf values
• Interpret Rf values
37.1.3Differences in Rf values
• Explain the differences in Rf values in terms of interaction with the stationary phase and of relative solubility in the mobile phase
37.2 Gas / liquid chromatography
• Describe and understand the terms: (a) stationary phase; a high boiling point non-polar liquid (on a solid support); (b) mobile phase; an unreactive gas; (c) retention time
• Interpret gas / liquid chromatograms in terms of the percentage composition of a mixture
• Explain retention times in terms of interaction with the stationary phase
37.3 Carbon-13 NMR spectroscopy
• Analyse and interpret a carbon-13 NMR spectrum of a simple molecule to deduce:: (a) the different environments of the carbon atoms present; (b) the possible structures for the molecule
• Predict or explain the number of peaks in a carbon-13 NMR spectrum for a given molecule
37.4 Proton NMR spectroscopy
• Interpret proton NMR to deduce proton environments, relative proton numbers, n + 1 splitting (singlet to multiplet), and possible structures.
• Predict the chemical shifts and splitting patterns of the protons in a given molecule
• Describe the use of tetramethylsilane, TMS, as the standard for chemical shift measurements
• State the need for deuterated solvents, e.g. CDCl ₃, when obtaining a proton NMR spectrum
• Describe the identification of O–H and N–H protons by proton exchange using D₂O