Illustrated Glossary of Organic Chemistry

Five zone analysis: The process of breaking an infrared spectrum into five zones and analyzing the peaks within each zone to determine the bonds and/or functional groups present or absent in the analyte.

A typical infrared spectrum divided into the five zones. Listed here are the bonds or functional groups considered for each zone.
Zone 1 (3700 - 32300 cm^-1): Alcohol O-H, terminal alkyne C-H, and amine/amide N-H
Zone 2 (3200 - 2700 cm^-1): Aryl/vinyl C-H, alkyl C-H, aldehyde C-H, and carboxylic acid O-H
Zone 3 (2300 - 2000 cm^-1): Alkyne C≡C and nitrile C≡N
Zone 4 (1850 - 1650 cm^-1): Carbonyl C=O
Zone 5 (1680 - 1450 cm^-1): Benzene ring and alkene C=C