17804-35-2

ChEBI: A member of the class of benzimidazoles that is the methyl ester of [1-(butylcarbamoyl)-1H-benzimidazol-2-yl]carbamic acid. A foliar fungicide used to control a wide range of Ascomycetes and Fungi Imperfecti in a wide range of crops.

Fungicide; ascaricide.

Colorless to white crystals or off-white powder. Faint acrid odor.

BENOMYL(17804-35-2) is incompatible with strong acids, peroxides and strong oxidizers. Decomposed by strong alkalis. Also decomposes on storage with water .

Insoluble in water.

High toxicity by ingestion. Upper respira- tory tract irritant, male reproductive, testicular, and embryo/fetal damage. Possible carcinogen.

Benomyl is used as an agricultural chemical and pesticide, pharmaceutical, and veterinary drug.

Literature sources indicate that this chemical is nonflammable.

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the Benomyl 367 skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9—Miscellaneous hazardous material, Technical Name Required.

Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides (forms toxic oxides of nitrogen). Decomposed in water or otherwise moist conditions.

Benomyl is a white crystalline solid. Faint acrid odor.

In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.

Mildly toxic in rodent by ingestion, inhalation, and absorption through skin; large dosescan produce effects of carbamate poisoning;teratogenic and mutagenic effects reported;carcinogenic potential not known; mild skinirritant.
LD50 oral (rat): 10,000 mg/kg
LD50 skin (mouse): 5600 mg/kg
LD50 skin (wild bird): 100 mg/kg
Benomyl metabolizes to carbendazim(MBC) and 5-HBC. Animal studies indicatedthat benomyl and its metabolites rapidlyeliminated out within 24 hours of exposure.They do not accumulate in tissues over longterm exposure..

Fungicide: Used as a pre-harvest systemic fungicide and as a post-harvest dip. Used on arable and vegetable crops, apples, soft fruit, nuts, mushrooms, lettuce, tomatoes and turf. In California, the top five crops for which benomyl is used are pistachios, table and raisin grapes, almonds, strawberries and wine grapes. All uses of benomyl products in the United States was phased out with a deadline of December 31, 2003. Not approved for use in EU countries.

ABORTRINE®; AGROCITE®; ARILATE®; BBC 6597®; BENEX®; BENLAT®[C]; BENLATE®, withdrawn 5/7/01; BENLATE 50®; BENLATE 50 W®; BENLATE 50WP®; BENOMYL® 50 W; BENOSAN®; D 1991®[C]; F 1991®; FUNDAZOL®; FUNGICIDE 1991®; FUNGACIDE D-1991®; FUNGOCHROM®; TARSAN®; TERSAN®; TERSAN 1991®; UZGN®

Benomyl was genotoxic, causing chromosome aberrations in vitro and in vivo, but it does not directly act with DNA.

Biological. Mixed cultures can grow on benomyl as the sole carbon source. It was proposed that benomyl degraded to butylamine and methyl 2-benzimidazole-carbamate (MBC), the latter undergoing further degradation to 2-aminobenzimidazole then to carbon dioxide and other products (Fuchs and de Vries, 1978).
Soil. In soil and water, benomyl is transformed to methyl-2-benzimidazole and 2- aminobenzimidazole (Rhodes and Long, 1974; Ramakrishna et al., 1979; Rajagopal et al., 1984). Benomyl is easily hydrolyzed in soil to methyl-2-benzimidazole carbamat
Plant. On apple foliage treated with a Benlate formulation, benomyl was transformed to MBC. Benomyl dissipated quickly and the reported half-life on foliage was 3–7 days (Chiba and Veres, 1981).
Chemical/Physical. In aqueous solutions, especially in the presence of acids, benomyl hydrolyzes to the strongly fungicidal methyl-2-benzimidazolecarbamate (carbendazim) (Clemons and Sisler, 1969; Peterson and Edgington, 1969; Zbozinek, 1984; Cremlyn, 1991; Worthing and Hance, 1991) and butyl isocyanate (Zbozinek, 1984; Worthing and Hance, 1991). The latter is unstable in water and decomposes to butylamine and carbon dioxide (Zbozinek, 1984). In highly acidic and alkaline aqueous solutions (pH <1 and pH >11), benomyl is completely converted to 3-butyl-2,4-dioxo-[1,2-a]-s-triazinobenzimida zole (STB) with smaller quantities of methyl 2-benzimidazolecarbamate (MBC). In addi tion 1-(2-benzimidazolyl)-3-n-butylurea was identified but only under highly alkaline conditions (Singh and Chiba, 1985).
Emits toxic fumes of nitrogen oxides when heated to decomposition (Lewis, 1990).

When benlate is degraded by the singlet oxygen photoreaction either in methanol or in aqueous hydrochloric solutions, carbendazim is identified as a major degradation product with the other nine degradation products from both reactions, including 2-guanidinobenzimidazole, benzimidazole, and 2,4'-and 2,5'-bibenzimidazoles which are identical to the photodegradation products of carbendazim by the singlet oxygen photoreaction in aqueous hydrochloric acid solution.

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Store in a cool, dry place or ina refrigerator away from strong bases, strong acids, heat.

Benomyl (1) was stable under strongly acidic conditions (i.e. 5N HCl; Singh et al., 1992). Under mildly acidic conditions, benomyl was converted into carbendazim (MBC, 2) through the loss of n-butyl isocyanate (3). The mechanism of this reaction involves interaction between the electron pair at the N-1 position and the proton on the n-butylcarbamoyl nitrogen. The formation of this hydrogen bond leads to proton abstraction and the release of 3 (Calmon and Sayag, 1976a). Under alkaline conditions, the formation of MBC became secondary to the formation of 3- butyl-2,4-dioxo-s-triazino[1,2-a]benzimidazole(4 ) such that compound 4 was the major degradate at pH 13 (Calmon and Sayag, 1976b; Singh and Chiba, 1985). The DT₅₀ values of benomyl at 25 °C in pH 5,7 and 9 solutions were 3.5, 1.5 and <1 hour, respectively (WHO, 1993). The relative stability of benomyl in strongly acidic solution was attributed to the protonation of the molecule (Singh et al., 1990).
Carbendazim (2) decomposed under alkaline conditions via the cleavage of the amide linkage to yield 2-aminobenzimidazole (2-AB, 5) (Watkins, 1976; Zbozinek, 1984). In pH 9 solution, the hydrolytic DT₅₀ for MBC was ca. 54 days (WHO, 1993). Under extreme alkaline conditions, compound 4 was converted into 1-(2-benzimidazolyl)-3-n-butylurea (6) via the cleavage of the carbamoyl moiety (White et al., 1973). Butyl isocyanate (3), once formed, hydrolysed rapidly in aqueous solution to yield n-butylcarbamic acid (7) and n-butylamine (8) (Calmon and Sayag, 1976a). These products are shown in Scheme 1.
Photolysis was not a significant degradation pathway for benomyl in sterile pH 5 solution (Powley, 1985) under natural sunlight.