Answer Page Infrared Spectroscopy Chem212

1a: 2-butanone: C=O 1750-1680 cm -1 2-methoxypropene: alkene C-H 3100-3020 cm -1

1b: alcohol: broad peak 2650-3400 cm -1 aldehyde: C=O and aldehyde C-H

1c: ethylamine: NH2 3500-3300 cm -1 acetonitrile: C_N at 2260-2210 cm -1

1d: benzene: aryl C-H 3030 cm -1 cyclohexane: alkyl C-H 2960-2850 cm -1

1e: 1-butyne: alkyne _C-H 3300 cm -1 and C_C butadiene: alkene C-H 3100-3020 cm -1 2-butyne: only C_C

1f: HC_CCH2NH2: alkyne and amine stretches CH3CH2C_N: nitrile stretch

1g: acetone: C=O propanal: C=O and aldehyde C-H

2a: identical 2b: different

3: _C-H 3300 cm -1; alkyl C-H 2960-2850; C_C 2260-2100; alkyl C-C fingerprint

4 top: hexanol bottom: nonane

5 top: tert-butyl ethyl ether bottom: 2-methyl-1-butanol

6 top: butanal bottom: 2-butanone

7 top: hexanoic acid bottom: benzoic acid

8 top: cyclohexene bottom: cyclohexane

9 left: octanoic acid right: 2-octanol

bottom: 2-octanone

10 top: 1-phenyl-2-butanone bottom: 1-phenyl-2-butanone (conjugated)

11 top: 5-hexen-2-one bottom: 2-cyclohexen-1-one (conjugated)

12 compound A has bands at 3090 cm-1 (=C-H) and 1650 cm-1: alkene
compound B has bands at 3300 cm-1 (_C-H) and 2100 cm-1 (C_C): alkyne
compound C has bands at 3330 cm-1 (-O-H) and 1060 cm-1 (C-O): alcohol
compound D has bands at 3080 cm-1 (=C-H) and 1640 cm-1 (C=C): alkene

13 compound I: 1740 cm-1 (C=O) and 1240, 1050 cm-1 (C-O): ester
compound J: 3325 cm-1 (=C-H) and 1060 (cm-1 C-O): no carbonyl; alcohol
compound K: 3100 cm-1 (=C-H) and 1640 cm-1 (C=C): alkene
compound L: 2720 cm-1 (O=C-H) and 1730 cm-1 (C=O): aldehyde

14 a. peaks above 3000 cm-1 suggests alkene C-H; also C=C
b. bands at 3300, 2150 indicate R-C_C-H: terminal alkyne
c. broad band at 3350 cm-1 shows -OH: alcohol
d. bands at 3080 and, 1640 cm-1: alkene
e. broad band at 3400 cm-1 shows -OH, band at 1020 cm-1 (C-O stretch), sharp band at 2120 cm-1 show C_C
thus 2 functional groups, alcohol and alkyne
f. stong band at 1720 cm-1 (C=O) could be an aldehyde or ketone
BUT the absence of bands at 2720 and 2820 cm-1 (C-H) shows it is not an aldehyde: therefore a ketone
g. strong band at 1725 cm-1 (C=O) and bands at 2720 and 2820 cm-1 (C-H): aldehyde

15 compound Q: 3335 (broad) (-O-H); 3080 (C=C-H); 1650 (C=O); 1048 (C-O): alcohol and alkene
compound R: 2200 (C_C); 1675 (C=O); no band at 3300; not a terminal alkyne; low value for carbonyl suggest conjugation with double/triple bond; absence of band at 2700 indicates a conjugated ketone, not aldehyde: alkyne and ketone
compound S: 3460 (broad) (-O-H); 1710 (C=O); no band at 2700, not aldehyde: ketone and alcohol
compound T: 3100 (C=C-H); 1740 (C=O); 1640 (C=C); 1240, 1040 (C-O): ester and alkene

16 spectrum 1: methyl pentanoate spectrum 2: 10-undecenal
spectrum 3: 3-methylcyclohexanone spectrum 4: 1-octanol
spectrum 5: 3-butenoic acid spectrum 6: octanoic acid

17 spectrum 1: dipropyl ether spectrum 2: 1,5-hexadiene
spectrum 3: cyclohexane spectrum 4: 1-hexen-3-ol
spectrum 5: 1-methyl-1-cyclopentene
not present: 3-hexanol, trans-4-octene

18 E: no units of unsaturation; 3325 (O-H); 1040 (C-O): an alcohol; possibly 1-butanol, 2-butanol, 2-methyl-1-propanol, t-butanol
F: one unit of unsaturation; 3325 (O-H); 1060 (C-O); an alcohol; no alkene stretch, must be cyclic; possible structures are cyclohexanol, isomeric methylcyclopentanols, cyclopentylmethanol, isomeric ethylcyclobutanols, isomeric ethylmethylcyclopropanols
G: one unit of unsaturation; 1700 (C=O), carbonyl accounts for unsaturation: no ring; no sign of aldehyde C-H, must be a ketone; possible structures: isomeric hexanones, isomeric methylpentanones
H: one unit of unsaturation; 2700 (H-C=O), 1740 (C=O), an aldehyde; possible structures: butanal, methylpropanal
M: 2 units of unsaturation; 3300 (_C-H); 2130 (C_C); triple bond, a terminal alkyne: only one possible structure: H-C_C-CH2Cl
N: one unit of unsaturation; 1715 (C=O); carbonyl accounts for unsaturation; no ring; probably an aldehyde such as pentanal
O: one unit unsaturation; carbonyl accounts; broad peak around 3000 suggest carboxylic acid; possible structures: pentanoic acid, methylbutanoic acids
P: 5 units of unsaturation; probably benzene ring plus carbonyl; need 2 oxygens, an ester?; possibly methyl benzoate