Section 13.15 Identifying Infrared Spectra 515Compound 3. The absorptions in the region in Figure 13.31 indicate
that hydrogens are attached to carbons but not to carbons. The
shape of the strong absorption band at is characteristic of an group.
The absorption at indicates that the compound has a triple bond. The
sharp absorption band at indicates that the compound is a terminal alkyne.
The compound is 2-propyn-1-ol.
3300 cm-^1' 2100 cm-^13300 cm-^1 O¬Hsp^312950 cm-^12 sp^23000 cm-^12.5 2.6 2.72.82.9 3 3.5 4 4.5 5 5.5 6 7 8 9 10 11 12 13 14 15 164000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600Wavelength (μm)Wavenumber (cm−^1 )% TransmittanceHC CCH 2 OHFigure 13.31
The IR spectrum of Compound 3.
2.5 2.6 2.72.82.9 3 3.5 4 4.5 5 5.5 6 7 8 9 10 11 12 13 14 15 164000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600Wavelength (μm)Wavenumber (cm−^1 )% TransmittanceOCH 3 CNHCH 3Figure 13.32
The IR spectrum of Compound 4.
Compound 4. The absorption in the region in Figure 13.32 indicates
that hydrogens are attached to carbons The relatively strong absorp-
tion band at suggests that the compound has one bond. The pres-
ence of the bond is confirmed by the absorption at The
absorption at indicates that the compound is an amide. The compound is
N-methylacetamide.
1660 cm-^1N¬H 1560 cm-^1. C“O3300 cm-^1 N¬Hsp^312950 cm-^12.3000 cm-^1Compound 5. The absorptions in the region in Figure 13.33 indi-
cate that the compound has hydrogens attached to carbons and
to carbons The absorptions at and indi-
cate that the compound contains a benzene ring. The absorption at for
the carbonyl group indicates that the compound is a ketone and that the carbonyl
group is not directly attached to the benzene ring. The absorption at
indicates that the compound contains a methyl group. The compound is 1-phenyl-
2-butanone.
' 1380 cm-^11720 cm-^1sp^3163000 cm-^12. 1605 cm-^11500 cm-^1sp^2173000 cm-^123000 cm-^1