MCAT Organic Chemistry Review 2018-2019

You should be able to identify these three peaks in an IR spectrum. If you need to identify other
peaks on Test Day, a list or table of peak wavenumbers will be provided.

Table 11.1. Absorption Frequencies

Functional  Group Wavenumber    (cm−1) Vibration

Alkanes 2800–3000

1200

C–H

C–C

Alkanes 3080–3140

1645

=C–H

C=C

Alkynes 3300

2200

≡C–H

C≡C

Aromatic 2900–3100

1475–1625

C–H

C–C

Alcohols 3100–3500 O–H  (broad)

Ethers 1050–1150 C–O

Aldehydes 2700–2900

1700–1750

(O)C–H

C=O

Ketones 1700–1750 C=O

Carboxylic  Acids 1700–1750

2800–3200

C=O

O–H (broad)

Amines 3100–3500 N–H    (sharp)

MCAT EXPERTISE

Infrared    spectroscopy    is  best    used    for identification  of  functional  groups. The most

important   peaks   to  know    are:

O–H (broad  around  3300    cm–1)

N–H (sharp  around  3300    cm–1)

C=O (sharp  around  1750    cm–1)