CAS 109-99-9: Tetrahydrofuran (THF) (C4H8O)

Identity

CAS Number	109-99-9
Molecular Formula	C4H8O
IUPAC Name	oxolane
Molecular Weight	72.11 g/mol
SMILES	`C1CCOC1`
Synonyms	THF, oxolane, tetrahydrofuran, butylene oxide

2D Structure

Physical Properties

Density	0.889 g/mL at 25°C
Boiling Point	66.0°C
Melting Point	-108.5°C
Flash Point	-14°C
Vapor Pressure	17.3 kPa at 20°C
Refractive Index	nD = 1.407
Dielectric Constant	ε = 7.52

Safety & GHS Classification

FlammableIrritantHealth Hazard

H225: Highly flammable liquid and vapor
H319: Causes serious eye irritation
H335: May cause respiratory irritation
H351: Suspected of causing cancer
H336: May cause drowsiness or dizziness

Storage: Store under nitrogen or argon atmosphere. THF forms explosive peroxides upon prolonged exposure to air and light — test for peroxides before distillation per ASTM E299. Add BHT inhibitor (0.025%) for extended storage. Keep away from ignition sources.