Title: Chlormezanone
CAS Registry Number: 80-77-3
CAS Name: 2-(4-Chlorophenyl)tetrahydro-3-methyl-4H-1,3-thiazin-4-one 1,1-dioxide
Additional Names: 2-(p-chlorophenyl)perhydro-3-methyl-1,3-thiazin-4-one 1,1-dioxide; 2-(4-chlorophenyl)-3-methyl-4-metathiazanone 1,1-dioxide; dichloromethazanone; chlormethazanone
Trademarks: Alinam (Lucien); Banabin-Sintyal; Fenarol (Winthrop); Lobak; Mio-Sed; Rexan; Rilansyl; Rilaquil; Rilassol; Supotran (Winthrop); Suprotan; Tanafol; Trancopal (Winthrop); Trancote (Sawai); Transanate (Teikoku Zoki)
Molecular Formula: C11H12ClNO3S
Molecular Weight: 273.74
Percent Composition: C 48.26%, H 4.42%, Cl 12.95%, N 5.12%, O 17.53%, S 11.71%
Literature References: Prepn starting with 4-chlorobenzylidenemethylamine: Surrey et al., J. Am. Chem. Soc. 80, 3469 (1958); GB 815203 (1959 to Sterling Drug).
Properties: Crystals, mp 116.2-118.2°. Soly in water at 25° less than 0.25% (w/v); in 95% ethanol at 25° less than 1.0% (w/v).
Melting point: mp 116.2-118.2°
Therap-Cat: Anxiolytic; muscle relaxant (skeletal).
Keywords: Anxiolytic; Muscle Relaxant (Skeletal).
Chlormidazole Chlornitrofen Chloroacetaldehyde Chloroacetamide Chloroacetanilide

Systematic (IUPAC) name
Clinical data
AHFS/ International Drug Names
Legal status Prescription only
Routes Oral
Pharmacokinetic data
Half-life 40.5 hours
CAS number 80-77-3 YesY
ATC code M03BB02
PubChem CID 2717
DrugBank DB01178
ChemSpider 2616 YesY
UNII GP568V9G19 YesY
KEGG D00268 YesY
Chemical data
Formula C11H12ClNO3S 
Mol. mass 273.737 g/mol
 N (what is this?)  (verify)

Chlormezanone (marketed under the brandname Trancopal or Fenaprim) is a drug used as an anxiolytic and a muscle relaxant.

Its use was discontinued in many countries from 1996 on, due to rare but serious cases of toxic epidermal necrolysis.