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Chapter 13 INFRARED SPECTROSCOPY 13.1 a) 3.33 X 10⁻³ cm b) 9.68 X 10¹⁴ c) 0.858 kcal/mol (3.59 kJ/mol) d) 92.3 kcal/mol (387 kJ/mol) 13.2 This frequency of light falls in the infrared region of the electromagnetic spectrum. 13.3 The energy of light with this frequency is 3.81 X 10⁻⁵ kcal/mol (1.60 X 10⁻⁴ kJ/mol). 13.4 a) The C-H bond absorbs at a higher wavenumber because hydrogen is a lighter atom than deuterium. b) The C=C bond absorbs at a higher wavenumber because a triple bond is stronger than a double bond. c) The C-CI bond absorbs at a higher wavenumber because the chlorine is a lighter atom than iodine and the C-CI bond is stronger than the C-I bond. 13.5 a) OH, 3000 cm⁻¹, very broad; =CH, 3100-3000 cm⁻¹; -CH, 3000-2850 cm⁻¹ b) =CH, 3100-3000 cm⁻¹; -CH, 3000-2850 cm⁻¹ c) NH₂, two bands, 3400-3250 cm⁻¹; =CH, 3100-3000 cm⁻¹ d) OH, 3550-3200 cm⁻¹, broad; =CH, 3100-3000 cm⁻¹; -CH, 3000-2850 cm⁻¹ e) NH, one band, 3400-3250 cm⁻¹; -CH, 3000-2850 cm⁻¹ f) -CH, 3000-2850 cm⁻¹; CHO, 2830-2700 cm⁻¹, two bands 13.6 The band in the triple bond region at 2150-2100 cm⁻¹ is much stronger for 1-hexyne than it is for the more symmetrical 3-hexyne. In addition, the =CH band near 3300 cm⁻¹ in the spectrum of 1-hexyne confirms the presence of the triple bond. 13.7 The 3000-2900 cm⁻¹ range is good region in the IR spectrum to monitor hydrocarbon emissions because most hydrocarbons have -CH bonds that absorb in this region. 13.8 a) The carbonyl group of this ketone is part of a five membered ring, so the band will be shifted about 30 cm⁻¹ to higher wavenumbers from the 205