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base position of 1715 cm⁻¹. The predicted position is 1745 cm⁻¹. b) This is a conjugated aldehyde, so the band will be shifted to lower wavenumbers by 20-40 cm⁻¹ from the base position of 1730 cm⁻¹. The predicted position is 1710-1690 cm⁻¹. c) This is a conjugated ketone, so the band will be shifted to lower wavenumbers by 20-40 cm⁻¹ from the base position of 1715 cm⁻¹. The predicted position is 1695-1675 cm⁻¹. d) This is a conjugated ester, so the band will be shifted to lower wavenumbers by 20-40 cm⁻¹ from the base position of 1740 cm⁻¹. The predicted position is 1720-1700 cm⁻¹. e) This is a conjugated carboxylic acid, so the band will be shifted to lower wavenumbers by 20-40 cm⁻¹ from the base position of 1710 cm⁻¹. The predicted position is 1690-1670 cm⁻¹. 13.9 a) The compound on the left, a ketone, has its carbonyl absorption near 1715 cm⁻¹ whereas the compound on the right, an aldehyde, has its carbonyl peak near 1730 cm⁻¹ and has two bands in the region of 2830- 2700 cm⁻¹. b) The ester on the left (non-conjugated) has its carbonyl absorption near 1740 cm⁻¹ whereas the ester on the right (conjugated) has its carbonyl absorption near 1720-1700 cm⁻¹. c) The compound on the right is a carboxylic acid and has a very broad band near 3000 cm⁻¹ whereas the compound on the left is a conjugated ester and will not show this feature. 13.10 a) =CH, 3100-3000; -CH, 3000-2850; C=O, 1695-1675; C=C, 1660-1640. b) -NH₂, 3400-3250 (two bands); =CH, 3100-3000; -CH, 3000-2850; aromatic ring, 1600-1450 (four bands), 900-675. c) =CH, 3100-3000, -CH, 3000-2850; C=C, 1660-1640; C-O, 1300-1000. d) OH, 3550-3200 (broad); -CH, 3000-2850; C-O, 1300-1000. e) =CH, 3300; -C-H, 3000-2850; C=C, 2150-2100; 1550, 1380. f) =CH, 3100-3000; -CH, 3000-2850; aldehyde CH, 2830-2700 (two bands); C=O, 1710-1690; aromatic ring, 1600-1450 (four bands), 900- 675. 13.11 a) 1-Butyne has absorptions at 3300 cm⁻¹ (=CH) and 2150-2100 cm⁻¹ (C=C) that are not present in the spectrum of 1-butene. b) Benzyl alcohol has absorptions at 3100-3000 (=CH), and 1600-1450 and 900-675 cm⁻¹ (aromatic ring) that are not present in the spectrum of t-butanol. 206