Fungicide

FRAC  7; oxathiin

NOMENCLATURE

Common name carboxin (BSI, E-ISO, ANSI); carboxine ((f) F-ISO); carbathiin (Canada); no name (Denmark, Germany)

IUPAC name 5,6-dihydro-2-methyl-1,4-oxathi-ine-3-carboxanilide 

Chemical Abstracts name 5,6-dihydro-2-methyl-N-phenyl-1,4-oxathiin-3-carboxamide 

CAS RN [5234-68-4]  Development codes D 735 

PHYSICAL CHEMISTRY

Composition Tech. grade is >97% pure.  Mol. wt. 235.3  M.f. C12H13NO2S  Form White crystals; (tech. is a white solid).  M.p. 91.5-92.5 ºC and 98-100 ºC depending on crystal structure  V.p. 0.025 mPa (25 ºC)  KOW logP = 2.2 (25 ºC)  Henry 2.96 ´ 10-5 Pa m3 mol-1 (calc.)  S.g./density 1.36  Solubility In water 199 mg/l (25 ºC). In acetone 177, methylene chloride 353, methanol 88, ethyl acetate 93 mg/l (25 ºC).  Stability Stable to hydrolysis (25 ºC) at pH 5, pH 7 and pH 9. Aqueous solutions (pH 7) exposed to light, DT50 <3 h.  pKa <0.5 

COMMERCIALISATION

History Fungicide reported by B. von Schmeling & M. Kulka (Science, 1966, 152, 659). Introduced by Uniroyal Chemical Co., Inc. (now part of CK Witco Corp.).  Patents US 3249499; US 3393202; US 3454391  Manufacturers Hindustan; Jin Hung; Kemira FC; Sundat; Uniroyal

APPLICATIONS

Mode of action Systemic fungicide.  Uses Seed treatment for control of smuts and bunts (particularly loose smut), at 50-200 g a.i./100 kg seed, on barley, wheat, and oats; seedling diseases (particularly Rhizoctonia spp.) of barley, wheat, oats, rice, cotton, peanuts, soya beans, vegetables, maize, sorghum, and other crops; and fairy rings on turf. The dimorphic forms do not differ in fungicidal activity.  Formulation types SC; FS; WP; Seed treatment.  Compatibility Not compatible with pesticides which are highly alkaline or acidic.  Selected tradenames: 'Vitavax' (Uniroyal); 'Hiltavax' (Hindustan); 'Kemikar' (Kemira FC)

OTHER TRADENAMES

'Oxatin' (Diachem) mixtures: 'Anchor' (+ thiram) (Uniroyal); 'Kick Start' (+ diazinon+ gamma-HCH) (Helena); 'Vitavax CT' (+ thiram) (Helena); 'Vitavax M DC' (+ captan) (Helena); 'Vitavax M' (+ thiram) (Helena); 'Zaprawa Oxafun T' (+ thiram) (Azot) Discontinued names mixtures: 'Vitavax RS' * (+ gamma-HCH+ thiram) (Uniroyal)

ANALYSIS

Product analysis by hplc or i.r. spectroscopy; details available from Uniroyal. Residue analysis by hydrolysis to aniline, which is determined by glc (H. R. Siskin & J. E. Newell, J. Agric. Food Chem., 1971, 19, 738; G. M. Stone, Anal. Methods Pestic. Plant Growth Regul., 1976, 8, 319). In drinking water, by gc with FID (AOAC Methods, 1995, 991.07). 

MAMMALIAN TOXICOLOGY

Oral Acute oral LD50 for rats 3820 mg/kg.  Skin and eye Acute percutaneous LD50 for rabbits >4000 mg/kg. Irritating to eyes (rabbits).  Inhalation LC50 (1 h) for rats >20 mg/l air.  NOEL In 2 y feeding trials, rats receiving 600 mg/kg diet showed no ill-effects.  ADI 0.01 mg/kg.  Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III 

ECOTOXICOLOGY

Birds Dietary LC50 (8 d) for mallard ducks >4640, bobwhite quail >10 000 mg/kg diet.  Fish LC50 (96 h) for rainbow trout 2, bluegill sunfish 1.2 mg/l.  Daphnia LC50 (48 h) 84.4 mg/l.  Algae EC50 (96 h) for Chlorella 2.4 mg/l; (5 d) for Selenastrum 0.48 mg/l.  Other aquatic spp. EC50 (14 d) for Lemna 0.92 mg/l.  Bees Not hazardous to bees when used as directed; LD50 >181 mg/bee.  Worms LC50 (14 d) for earthworms 500-1000 ppm. 

ENVIRONMENTAL FATE