IR peaks to know

2900

sp3 C-H stretch (alkane)

1500

C-H bends (alkane)

3100

sp2 C-H stretch (alkene)

2900

sp3 C-H stretch (alkene)

1600

C=C stretch (alkene)

1450

C-H bend (alkene)

3100

sp2 C-H stretch (aromatic rings)

2900

sp3 C-H stretch (aromatic rings)

1400 to 1600

aromatic C=C stretch (aromatic rings)

3400 (broad)

O-H stretch (alcohols)

2900

sp3 C-H stretch (alcohols)

1000 to 1100

C-O stretch (alcohols)

3000-3100

O-H stretch (carboxylic acids)

2900

sp3 C-H stretch (carboxylic acids)

1200

C-O stretch (carboxylic acids)

1700

C=O stretch (carboxylic acids)

2900

sp3 C-H stretch (aldehydes)

1720

C=O stretch (aldehydes)

2900

sp3 C-H stretch (ketones)

1700

C=O stretch (ketones)

1750

C=O stretch (ester)

1000 to 1200

C-O stretch (ester)

2900

sp3 C-H stretch (amine)

3400

N-H stretch (amine)

3200 - 3400

N-H stretch (amide)

2900-3000

sp3 C-H stretch (amide)

1600-1700

C=O stretch (amide)

2200-2300

C≡N stretch (nitrile)