SPECTROSCOPY

7.47

TABLE 7.20 Absorption Frequencies of Single Bonds to Hydrogen (Continued)

Group	Band, cm 1			Remarks
	Miscellaneous R9H
9S9H	2600–2550	(w)		Weaker than OH and less affected by H
				bonding
P9H	2440–2350	(m)		Sharp
O
P	2700–2560	(m)		Associated OH
OH
R9D	100/137 times the			Useful when assigning RH bands; deutera-
	corresponding RH			tion leads to a known shift to lower fre-
	frequency			quency

TABLE 7.21 Absorption Frequencies of Triple Bonds
	Abbreviations Used in the Table
m, moderately strong			var, of variable strength
m–s, moderate to strong			w–m, weak to moderately strong
s, strong
Group	Band, cm 1			Remarks
Alkynes
Terminal	3300 (s)			CH stretching
	2140–	2100 (w–m)*		C#C stretching
	1375–	1225 (w–m)
	695–	575 (m–s)		Two bands if molecule has axial
				symmetry
	ca 630 (s)			Alkyl monosubstituted
Nonterminal	2260–	2150 (var)*		Symmetrical or nearly symmetrical sub-
				stitution makes the C#C stretching
				frequency inactive. When more than
				one C#C linkage is present, and
				sometimes when there is only one,
				there are frequently more absorption
				bands in this region than there are
				triple bonds to account for them.
R1 9C #C 9R2	540–	465 (m)		The longer the chain, the lower the fre-
				quency
Aryl9C #C9	ca 550 (m)
	ca 350 (var)
9C#C 9halogen (Cl, Br, I)	185–	160 (var)

* Conjugation with olefinic or acetylenic groups lowers the frequency and raises the intensity. Conjugation with carbonyl groups usually has little effect on the position of absorption.

7.48					SECTION 7
TABLE 7.21 Absorption Frequencies of Triple Bonds (Continued)
	Group			Band, cm 1				Remarks
Nitriles	9C#N			2260–	2200		(var)	Stronger and toward the lower end of the
								range when conjugated; occasionally
								very weak or absent
Aliphatic				580–	555	(m–s)
				560–	525	(m–s)
				390–	350	(s)
Aromatic				580–	540	(s)
				430–	380	(m)
Isonitriles				2175–	2150		(s)	Very sensitive to changes in substituents
	R9N #C
or R9N"C:				2150–	2115		(s)	Not found for nitriles
					1595
Cyanamides
N 9C #N L				2225–	2210		(s)
		N 9C "N
Thiocyanates
R9S9C #N				2175–	2140		(s)	Aryl thiocyanates at the upper end of the
								range, alkyl at the lower end
				404–	400	(s)		Aliphatic derivatives
				ca 600 (m–s)
Nitrile N-oxides
9C#N:O				2305–	2285		(s)	Aryl derivatives
				1395–	1365		(s)
Diazonium salts
				2300–	2230		(m–s)
R9N#N
Selenocyanates
R9Se9C #N				ca 2160 (m–s)
				545–	520
					ca 390
					ca 350

					SPECTROSCOPY					7.49
TABLE 7.22	Absorption Frequencies of Cumulated Double Bonds
					Abbreviations Used in the Table
				m–s, moderate to strong				vs, very strong
				s, strong				w, weak
Group					Band, cm 1					Remarks
Carbon dioxide
O"C "O					2349 (s)					Appears in many spectra as a result of
										inequalities in path length
Isocyanates
9N"C "O					2275–	2250	(vs)			Position unaffected by conjugation
Isoselenocyanates
9N"C "Se					2200–	2000	(s)			Broad; usually two bands
					675–	605
Azides
9N3 or 9N "N "N					2140–	2030	(s)
					1340–	1180	(w)			Not observed for ionic azides
9N"C "N9					2155–	2130	(s)			Split into unsymmetrical doublet by
										conjugation with aryl groups:
										2145–2125 (vs) and 2115–2105
										(vs)
Isothiocyanates
9N"C "S					2140–	1990	(vs)			Broad; usually a doublet
					649–	600 (m–s)
					565–	510 (m–s)
					470–	440 (m–s)
Ketenes
C "C "O					ca 2150 (s)
Ketenimines
C"C "N9					2050–	2000	(s)
Allenes
C "C "C					2000–	1915	(m–s)			Two bands when terminal allene or
										when bonded to electron-attracting
										groups
Thionylamines
9N"S"O					1300–	1230	(s)
					1180–	1110	(s)
Diazoalkanes
					2030–	2000	(s)
R2C "N "N
					2050–	2035	(s)
9CH"N "N
Diazoketones
					2100–	2080				Monosubstituted
9CO9CH"N "N
					2075–	2050				Disubstituted

7.50		SECTION 7
TABLE 7.23	Absorption Frequencies of Carbonyl Bands
All bands quoted are strong.
Groups		Band, cm 1	Remarks
Acid anhydrides
9CO9O9CO9
Saturated		1850–1800	Two bands usually separated by about 60
		1790–1740	cm 1. The higher-frequency band is more
			intense in acyclic anhydrides, and the
			lower-frequency band is more intense in
			cyclic anhydrides.
Aryl and , -unsaturated		1830–1780
		1790–1710
Saturated five-ring		1870–1820
		1800–1750
All classes		1300–1050	One or two strong bands due to CO stretching
Acid chlorides	9COCl
Saturated		1815–1790	Acid fluorides higher, bromides and iodides
			lower
Aryl and , -unsaturated		1790–1750
Acid peroxide
CO9O9O9CO9
Saturated		1820–1810
		1800–1780
Aryl and , -unsaturated		1805–1780
		1785–1755
Esters and lactones
9CO9O9
Saturated		1750–1735
Aryl and , -unsaturated		1730–1715
Aryl and vinyl esters
C"C 9O9CO 9alkyl		1800–1750	The C"C stretching band also shifts to
			higher frequency.
Esters with electronegative
substituents; e.g.,
CCl 9CO 9O 9		1770–1745
-Keto esters		1755–1740
Six-ring and larger lactones		Similar values to the
		corresponding
		open-chain esters
Five-ring lactone		1780–1760
, -Unsaturated five-ring
lactone		1770–1740	When -CH is present, there are two bands,
			the relative intensity depending on the sol-
			vent.
, -Unsaturated five-ring
lactone, vinyl ester type		ca 1800
Four-ring lactone		ca 1820
-Keto ester in H bonding
enol form		ca 1650	Keto from normal; chelate-type H bond
			causes shift to lower frequency than the
			normal ester. The C"C band is strong and
			is usually near 1630 cm 1.
All classes		1300–1050	Usually two strong bands due to CO stretch-
			ing

				SPECTROSCOPY		7.51
TABLE 7.23		Absorption Frequencies of Carbonyl Bands (Continued)
	Groups			Band, cm 1		Remarks
Aldehydes	9CHO
(See also Table 7.49 for
C9H.) All values given
below are lowered in liq-
uid-film or solid-state
spectra by about 10–20
cm 1. Vapor-phase spec-
tra have values raised
about 20 cm 1.
Saturated				1740–1720
Aryl				1715–1695		o-Hydroxy or amino groups shift this value to
						1655–1625 cm 1 because of intramolecular
						H bonding.
, -Unsaturated				1705–1680
, , , -Unsaturated				1680–1660
-Ketoaldehyde in enol
form				1670–1645		Lowering caused by chelate-type H bonding
Ketones	C		O
All values given below
are lowered in liquid-film
or solid-state spectra by
about 10–20 cm 1. Va-
por-phase spectra have
values raised about 20
cm 1.
Saturated				1725–1705
Aryl				1700–1680
, -Unsaturated				1685–1665
, , , -Unsaturated and
diaryl				1670–1660
Cyclopropyl				1705–1685
Six-ring ketones and larger				Similar values to the
				corresponding
				open-chain ke-
				tones
Five-ring ketones				1750–1740		, Unsaturation, , , , unsaturation, etc.,
						have a similar effect on these values as on
						those of open-chain ketones.
Four-ring ketones				ca 1780
-Halo ketones				1745–1725		Affected by conformation; highest values are
						obtained when both halogens are in the
						same plane as the C"O.
, -Dihalo ketones				1765–1745
1,2-Diketones, syn-trans-
open chains				1730–1710		Antisymmetrical stretching frequency of both
						C"O’s. The symmetrical stretching is in-
						active in the infrared but active in the
						Raman.
syn-cis-1,2-Diketones, six-
ring				1760 and 1730
syn-cis-1,2-Diketones, five
ring				1775 and 1760

7.52							SECTION 7
TABLE 7.23 Absorption Frequencies of Carbonyl Bands (Continued)
		Groups					Band, cm 1	Remarks
Ketones		C			O (continued)
o-Amino-aryl or o-hydroxy-
aryl ketones							1655–1635	Low because of intramolecular H bonding.
								Other substituents and steric hindrance af-
								fect the position of the band.
Quinones							1690–1660	C"C band is strong and is usually near
								1600 cm 1.
Extended quinones							1655–1635
Tropone							1650	Near 1600 cm 1 when lowered by H bonding
Carboxylic acids						9CO2H		as in tropolones
All types							3000–2500	OH stretching; a characteristic group of small
								bands due to combination bands
Saturated							1725–1700	The monomer is near 1760 cm 1, but is rarely
								observed. Occasionally both bands, the free
								monomer, and the H-bonded dimer can be
								seen in solution spectra. Ether solvents
								give one band near 1730 cm 1.
, -Unsaturated							1715–1690
Aryl							1700–1680
-Halo-							1740–1720
Carboxylate ions						9CO2
Most types							1610–1550	Antisymmetrical and symmetrical stretching,
Amides							1420–1300	respectively
		CO				N
(See also Table 7.49 for
NH stretching and bend-
ing.)
Primary 9CONH2
In solution							ca 1690	Amide I; C"O stretching
Solid state							ca 1650
In solution							ca 1600	Amide II: mostly NH bending
Solid state							ca 1640	Amide I is generally more intense than amide
								II. (In the solid state, amides I and II may
								overlap.)
Secondary 9CONH9
In solution							1700–1670	Amide I
Solid state							1680–1630
In solution							1550–1510	Amide II; found in open-chain amides only
Solid state							1570–1515	Amide I is generally more intense than amide
								II.
Tertiary							1670–1630	Since H bonding is absent, solid and solution
								spectra are much the same.
Lactams
Six-ring and larger rings							ca 1670
Five-ring							ca 1700	Shifted to higher frequency when the N atom
Four-ring							ca 1745	is in a bridged system
R9CO9N9C"C								Shifted 15 cm 1 by the additional double
								bond
C"C9CO9N								Shifted by up to 15 cm 1 by the additional
								double bond. This is an unusual effect by
								, unsaturation. It is said to be due to the
								inductive effect of the C"C on the well-
								conjugated CO9N system, the usual con-
								jugation effect being less important in such
								a system.