Description
Ethiofencarb, α-ethylthio o-tolyl methylcarbamate
(IUPAC), C11H25N02S, MW 225.3, mp 33.4 ?C,
forms colorless crystals that are moderately soluble in
water, are fairly soluble in hexane, and are readily soluble
in dichloromethane, isopropanol, and toluene.
Uses
Ethiofencarb is a kind of Systemic insecticide ,used to control aphids on fruit crops.
Uses
Ethiofencarb is a systemic insecticide with contact and stomach
action. It is used to control aphids on fruit, vegetables, ornamentals and
sugar beet.
Definition
ChEBI:Ethiofencarb is a carbamate ester. It has a role as a carbamate insecticide, an EC 3.1.1.7 (acetylcholinesterase) inhibitor and an agrochemical. It is functionally related to a methylcarbamic acid and a 2-[(ethylsulfanyl)methyl]phenol.
Preparation
Ethiofencarb is produced by reaction of 2-chloromethyl
phenol with sodium ethylmercaptide to form 2-ethylthio
methylphenol, which in turn is reacted with methylisocyanate.
Environmental Fate
Plant. Degrades in plants to the sulfone and sulfoxide (Hartley and Kidd, 1987).
Metabolic pathway
Ethiofencarb is metabolised by rapid oxidation at sulfur, hydrolysis of the
carbamate group to give phenols, hydroxylation of the N-methyl moiety
and conjugation.
Degradation
Ethiofencarb is stable in neutral and acidic but is hydrolysed under basic
conditions. DT50 values at pH 7 and 11.4 (37 °C) were 450 hours and
5 minutes, respectively. The kinetics of hydrolysis of ethiofencarb in
pure water and in aqueous solutions at pH 2,6,9,12 and at temperatures
in the range 4-50°C were studied. No acid hydrolysis was observed.
Ethiofencarb was rapidly hydrolysed at pH 9 and 12. Ethiofencarb in
pure water at room temperature reached an equilibrium with 80%
remaining undegraded (Sanz-Asensio et al., 1997).
Photodegradation of aqueous solutions in sunlight is rapid (PM). The
oxidative photodegradation of ethofencarb was studied in aqueous
acetonitrile using anthraquinone to mimic natural photosensitisers. Solutions
were irradiated with a Hg lamp (400 W) for 48 minutes. The
emission spectrum of the lamp was not described. Reaction products
were identified by GC-MS methods. The main products were 2-
hydroxybenzaldehyde (2) and 3-methylbenzo[e-1,3]oxazine-2,4-dione(3)
(see Scheme 1). Products resulted from photocleavage of the CH,-S bond
and/or the C-O bond followed by hydrogen atom abstraction and
photo-oxidation. An electron-acceptor photosensitiser may increase rates
of photodegradation (Galadi and Julliard, 1996). Solutions of ethiofencarb
in cyclohexane, cyclohexene or isopropanol were irradiated with a high
pressure Hg lamp (cut-off filter <280 nm) or natural sunlight (Germany,
May-July). Analysis was by HPLC with diode-array detection, NMR, IR
and MS. Half-lives of photodegradation were in the range 20 minutes
to more than 20 hours. The predominant reaction (Scheme 1) was
photo-oxidation of ethiofencarb to its sulfoxide (4). The cyclic dione (3)
was a product of oxidation at the benzylic position. Ethiofencarb was
photo-oxidised in cyclohexane to the sulfoxide (4) and the sulfone (5) and
their corresponding phenols (8 and 9), the latter being a minor product.
Subsequently the cyclised dione (3) was formed. In isopropanol,
reaction with solvent gave addition products (6 and 7) and an unusual
bis-diethylthio compound (10) (Kopf and Schwack, 1995).
