13.19 Infrared Spectroscopy

	Gives information about the functional groups in a molecule

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Infrared Spectroscopy

	region of infrared that is most useful lies between 2.5-16 mm (4000-625 cm-1)
	depends on transitions between vibrational energy states
		stretching
		bending

Stretching Vibrations of a CH2 Group

Bending Vibrations of a CH2 Group

Bending Vibrations of a CH2 Group

Fig. 13.26 (page 520)

"Hexane"

	Hexane

"Hexane"

	Hexane

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Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Stretching vibrations (single bonds)
	sp C�H 3310-3320
	sp2 C�H 3000-3100
	sp3 C�H 2850-2950
	sp2 C�O 1200
	sp3 C�O 1025-1200

Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Stretching vibrations (multiple bonds)

Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Stretching vibrations (carbonyl groups)
	Aldehydes and ketones 1710-1750
	Carboxylic acids 1700-1725
	Acid anhydrides 1800-1850 and 1740-1790
	Esters 1730-1750
	Amides 1680-1700

Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Bending vibrations of alkenes

Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Bending vibrations of derivatives of benzene
	Monosubstituted 730-770 and 690-710
	Ortho-disubstituted 735-770
	Meta-disubstituted 750-810 and 680-730
	Para-disubstituted 790-840

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Table 13.4 (p 519) Infrared Absorption Frequencies

	Structural unit Frequency, cm-1
	Stretching vibrations (single bonds)
	O�H (alcohols) 3200-3600
	O�H (carboxylic acids) 3000-3100
	N�H 3350-3500

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