Organic Chemistry IR Functional Groups

Alkanes

peak right under 3000 (in every molecule)

Alkenes

peak right above 3000 (shoulder peak)

paired with very sharp peak ~1620-1670

Aromatics

peak right above 3000 (shoulder peak)

paired with “upside down u” peaks on 1600 and ~1500-1450 that are very sharp

Alkynes

sharp peak ~3300

paired with very sharp peak ~2000 to 2200

Alcohol

broad peak with meduim intensity with tip at ~3300 (coming back up before 3000)

Amine

broad peak with tip at ~3300 (if two peaks, then primary , if one peak the secondary)

Ketone

strong and sharp peak at ~1710

Aldehyde

strong and sharp peak at ~1725

paired with peak at ~2700 (nothing else shows up in this spot!)

Carboxylic Acid

very broad peak from 3500 to 2400

paried with sharp and strong peak at ~1710 

Ester

strong and sharp peak at ~1740 (higher than ketone can be)

Amide

has peaks like amine

paried with strong and sharp peak ~1650

Nitriles

peak ~2260 to 2100