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3. D HeptaldehydeThe intense carbonyl C=O stretch peak at ~1725 cm-1 suggests either an aldehyde, or possibly aketone (although it is a little higher frequency than a standard ketone). The aldehyde is indicatedby the two aldehyde C-H stretch absorptions which appear at 2750 & 2850 cm-1. Note that thepeak at 2850 cm-1 appears as a shoulder on the much more intense absorption corresponding tothe symmetric CH2 stretching vibration.

AliphaticC-H stretching

Aldehyde C-H Stretch

Aldehyde C=O stretch

CH 2 Bending

4 . M Benzyl AlcoholNote the broad O-H stretch absorption and the olefinic C-H stretch absorptions. This spectrumcan be differentiated from that for allyl alcohol by observing the combination and overtone bandsfrom 1600-2000cm-1, which are indicative of a monosubstituted benzene. In addition the C=C

ring stretch at about 1600 + 1475cm-1 indicate that it is an aromatic ring.

C-O Stretch (1)

C-C stretchAromatic ring breath

C-O Stretch (1)

Aromatic C-H stretch

C-H OOP

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5 L Butyl acetateNote the presence of a C=O stretch at about 1750-1760cm -1. This would tend to indicate thepossibility of an ester functional group, or possibly a strained ring ketone. The broad and intenseC-O stretch absorption at about 1250cm-1is a strong indicator of an ester group. This band is theC-O stretch corresponding to the bond of the ester oxygen and the carbonyl carbon. In addition,the C-O stretch at about 1050cm-1 is due to the other C-O stretch to a 1 carbon.

Aliphatic C-H stretch

C-O stretch 1

C-O stretch tocarbonyl carbon

C=O stretch

6 B 3-PentanoneNote the presence of a C=O stretch at about 1710-1720cm -1. This would tend to indicate thepossibility of an ketone, aldehyde, or possibly a conjugated ester. There are no absorptions at2850 and 2750cm-1 which would correspond to the aldehyde C-H stretch, thus it is not likely tobe an aldehyde. There are no olefinic C-H stretch absorption bands above 3000cm-1, nor arethere any C=C stretch absorptions around 1600 to 1650cm-1. Thus it is not likely a conjugatedester (also note the lack of strong C-O stretch absorptions at 1250cm-1 in the ester). Thecompound is likely a ketone.

C=O stretch

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7. F Propanoic AcidThe broad O-H absorption from 2400 to 3400cm-1 is a dead giveaway for a carboxylic acid. Notealso the relatively broad C=O at about 1710cm-1 and the C-O stretch at 1250cm-1.

Broad O-H stretchof acid dimer

C-H stretch

C=O stretch

C-O stretch

8 H 1-ButanolNote the broad alcohol O-H stretch at 3200-3500cm-1. More importantly, note the 1 alcohol C-O stretch at ~1050cm-1.

O-H stretch

C-O Stretch (1)

9. I CyclohexaneNote the simplicity of the spectra, only C-H stretch and bend absorptions. The most importantaspect of this spectrum is what is NOT present. Note the absence of a CH3 bend at 1375 cm-

1.

This would suggest a ring structure.

CH 2Scissoring bend

C-H stretch

NO CH3SYMMETRIC

BEND

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10 . E 2-ButanolNote the broad alcohol O-H stretch at 3200-3500cm-1. More importantly, note the 2 alcohol C-Ostretch at ~1100cm-1.

O-H stretch

C-O Stretch (2)

11. C 1-Hexene1-Hexene has an ir spectrum very similar to cyclooctene, but can be differentiated from it by closeexamination of the spectrum. 1-Hexene has a CH

3

symmetric umbrella bend at 1375cm-1. Also

note if you will, that the unsymmetric double bond C=C stretch of 1-heptene is more intense thanthe symmetric C=C stretch in cyclooctene.

Olefinic C-Hstretch

C=C stretch

CH 3 bend

12 . J 2-Methyl-2-butanolNote the broad alcohol O-H stretch at 3200-3500cm-1. More importantly, note the 3 alcohol C-Ostretch at ~1150cm-1.

O-H stretch

C-O Stretch (3)

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