AromaticsProminent (strong) features:

C-H stretch 3100-3000

in-plane C-H bend 1300-1000

out of plane C-H bend 900-675

C=C ring stretches 1600-1585 and 1500-1400

out of plane C=C bend 450-400

combination bands

IR of AlcoholsO-H H-bonded 3331

O-H bend overlapsC-H bend 1209

C-O stretch 1023

IR of Alcohols

O-H non-hydrogen bonded or free OH 3650-3584(sharp bands in gas phase)

Intermolecular H-Bonding in solution increase with concentration gives bands at 3550-3200 (broader)

cyclohexylcarbinol

Ethers and Epoxides

Ethers: C-O-C asymmetric stretch 1150-1085 (strong)C-O-C symmetric stretch is usually weak at 1075-1000

Epoxides: ring stretch near 1250 and 950-810

O

Carbonyl GroupsKetones, aldehydes, carboxylic acids, carboxylic esters,lactones, acid halides, anhydrides, amides, lactamsall show C=O stretch 1870-1540

RC

O

R RC

O

H RC

O

OH

RC

O

OR

C

O

O

RC

O

Cl RC

O

O RC

O

RC

O

NH2

IR of 2-Pentanone

C=O stretch 1717 C-CO-C stretch 1171

Carbonyl Groupsnormal aliphatic ketones (acetone, cyclohexanone) 1715

replacement of alkyl group by heteroatom (G) shifts C=O stretch

direction depends on inductiveor resonance effect inductive: increases C=O freq. resonance: decreases

G

C O

R

+G

C O-

R

Effect of G

G C=O

Cl 1815-1785F 1869Br 1812OH (monomer) 1760OR 1750-1735

NH2 1695-1650SR 1720-1690

G

C O

R

+G

C O-

R

Inductive

Resonance

Aldehydes

C=O stretch 1724C(O)-H stretch2825, 2720

C-H bend 760

Aldehydes slightly higher freq. than methyl ketones

overtone band

combination bands

Carboxylic Acids

Broad OH absorption due to H-bonding 3300-2500

C=O stretch near 1760 ( aliphatic monomer)reduced to 1700 (aliphatic dimers)

intramolecular H-bonding is usually strongerC=O stretch can be reduced to 1680

Acid Halide

C=O stretch 1774C-H stretch3065

Fermi Resonanceovertone of 872

EstersC=O stretch 1765

C-H stretchesO-C=C asymmetricstretch 1193

Amines

octylamine

N-H Stretch (as) 3372, (ss) 3290

N-H Bend 1617

N-H wag900-700

C-N stretch 1073

Aliphatic C-H bands

NitrilesCN stretch 2226

Aromatic C-H bands

IR of Benzylthiol

S-H Bend 2565

Aromatic C-H bandsAliphatic C-H bands

Aromatic overtones

IR of p-toluenesulfonate

S=O stretch 1355, 1177

S-C-O stretch

Sample 1a

SolutionBand at 2200 suggests CC

bands at 3300 suggest H-CC

bands around 3000 aliphatic C-H

one possibility:

C CH2C

Cl

HC3H3Cl

Sample 1b

Solution

High frequency bands suggest aromatic C-H and aliphatic C-H

bands around 1600 suggest substituted aromatic

one possibility:

C10H14

Sample 1c

Solution

High frequency bands suggest N-H, aromatic C-H and aliphatic C-H

bands around 1600 suggest substituted aromatic

one possibility: NH2

C7H9N

Sample 1d

Solution

High frequency bands suggest O-H, aromatic C-H and aliphatic C-H

bands around 1600 suggest substituted aromatic

one possibility: OH

C7H8O

Sample 1e

Solution

High frequency bands suggest N-H, aromatic C-H and aliphatic C-H

Note: N-H band is sharp…

bands around 1600 suggest substituted aromatic

one possibility: HN

C8H11N

Sample 1f

Solution

High frequency bands suggest aromatic C-H and aliphatic C-H

bands around 1600 suggest substituted aromatic

one possibility:

Cl

C7H7Cl

Sample 1g

Solution

High frequency bands suggest H-bonding and O-H and aliphatic C-H

O2 suggest acid? But band at 1728 suggests strongC=O ….perhaps inductive effect of Cl

one possibility:

O

OH

Cl

C3H5O2Cl

Sample 1h

Solution

High frequency bands suggest H-bonding and O-H and aliphatic C-H

O suggest alcohol?

Note: no unsaturation

one possibility:

OHC5H12O

Sample 1i

Solution

High frequency bands suggest aliphatic C-H

band at 1718 suggests ketone

band at 1650 suggest some unsaturation

one possibility:

OC6H10O

Sample 1j

Solution

High frequency bands suggest aromatic and aliphatic C-H

bands at 1500-1400 suggest aromatic

one possibility:

C10H12

Sample 1k

Solution

High frequency bands suggest aliphatic C-H

bands at 2300 suggest CN

second N; note no evidence of N-H

one possibility:

C

N

N

C5H10N2