Q6(h). IR distinction: hydrogen bonding and ring strain
How can you distinguish between the following pairs on the basis of their IR spectra? (i) [salicylic acid and 4-hydroxybenzoic acid] (ii) [cyclobutanone and cyclohexanone] [structures given in the paper]
Answer in brief
(i) Salicylic acid: O–H and C=O bands lowered by chelation, unchanged on dilution. (ii) Cyclobutanone absorbs near 1780 cm⁻¹, cyclohexanone near 1715 cm⁻¹.
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CoversIR spectroscopyhydrogen bondingsalicylic acidring straincarbonyl stretching frequencycyclobutanone
All parts of Question 6
- 6(a) Singlet and triplet carbenes; fluorenylidene with cis-but-2-ene4 marks
- 6(b) Bromine addition: styrene reacts faster than propene4 marks
- 6(c) Addition of HCl to an α,β-unsaturated acid4 marks
- 6(d) Michael addition of a cyclic 1,3-dione to cyclohex-2-enone4 marks
- 6(e) Hydroboration–oxidation of 1-methylcyclohexene4 marks
- 6(f) Cope rearrangement of a 1,5-diene4 marks
- 6(g) Diels–Alder reaction: product and reactants4 marks
- 6(h) IR distinction: hydrogen bonding and ring strain4 marks
- 6(i) McLafferty rearrangement: 2-pentanone and 3-pentanone4 marks
- 6(j) NMR assignment of 4-methylpent-1-yne4 marks