Description
Cartap is a largely obsolete insecticide. It is highly soluble in water, has a low volatility and tends not to persist in soil systems. There are data gaps regarding its human health effects but is known to be moderately toxic. There are also data gaps regarding its ecotoxicity but is highly toxic to aquatic vertebrates and moderately toxic to fish.
Chemical Properties
Cartap is typically prepared as its hydrochloride salt, which appears as white crystals with a slightly pungent odor. Its melting point is 183-183.5°C (decomposition) (the original melting point is 179-181°C). It is slightly soluble in methanol, poorly soluble in ethanol, and insoluble in organic solvents such as acetone, ether, chloroform, hexane, and benzene. Its solubility in water at 25°C is 200g/L. It is stable in acidic media but unstable in alkaline media. It remains unchanged after storage at 40°C and 60°C for three months, and remains unchanged when stored sealed at room temperature. It is slightly hygroscopic and corrosive to metals such as iron. The melting point of its free base is 130.5-131°C.
Uses
Cartap hydrochloride is used to control sucking and chewing
insects (particularly Lepidoptera and Coleoptera), at almost all stages of
development, on many crops including rice, potatoes, cabbage and other
vegetables. It is also used on soya, peanuts, sunflower, maize, sugar beet,
wheat, pearl barley, pome, stone and citrus fruit, vines, tea, chestnuts,
ginger, cotton and sugar cane.
Production Methods
Cartap, commonly formulated as cartap hydrochloride, is produced through a multi-step chemical synthesis involving amination and thiocarbamate formation. The process begins with the reaction of propylene chloride with dimethylamine and an alkali solution at low temperatures, followed by heating to around 45 DegC to complete the amination step. This yields an intermediate compound that is further reacted to cartap hydrochloride.
Agricultural Uses
Insecticide: Cartap hydrochloride is used to control chewing and sucking insects on many crops, including rice, potatoes, cabbage and other vegetables, soy beans, peanuts, sunflowers, maize, sugar beet, wheat, pearl barley, pome fruit, stone fruit, citrus fruit, vines, chestnuts, ginger, tea, cotton, and sugar cane. Not currently registered in the U.S. or registered for use in EU countries. There are approximately 15 global suppliers.
Trade name
CADAN®; CALDAN®; KRITAP®; NTD 2®; PADAN®; PATAP®; SANVEX®; THIOBEL®; TI1258®; VEGETOX®
Mechanism of action
Phytotoxic. Nicotinic acetylcholine receptor (nAChR) channel blocker.
Safety Profile
Poison by ingestion andintravenous routes. An experimental teratogen. Aninsecticide. When heated to decomposition it emits verytoxic fumes of NOx, SOx, and HCl.
Metabolic pathway
Nereistoxin, 4-N,N-dimethylamino-1,2-dithiolane, is
produced from cartap hydrochloride as a main product
through photoreaction under UV irradiation in aqueous
and methanolic solutions, and on glass and silica gel
surfaces. Cartap hydrochloride is also oxidized with
N-bromosuccinimide (NBS) to give nereistoxin.
Degradation
Cartap hydrochloride was hydrolysed to dihydronereistoxin (2) when
automatically titrated with sodium hydroxide solution and subsequently
oxidised to nereistoxin (3) (see Scheme 1). The hydrolysis was a base
catalysed pseudo-first-order reaction with a half-life of 10 minutes at pH 7
and 25 °C. Nereistoxin was so stable that no degradation was observed
after 24 hours at 100 °C and with pH in the range 1-4. The DT50 s of nereistoxin at 100 °C and at the higher pH values of 7/10 and 12.3 were 26,20
and 7.9 hours, respectively. It was predicted that nereistoxin (3) would
be hydrolysed by alkali to the 3-mercaptopropanesulfenic acid (4) which
would be oxidised to the sulfinic acid (5) and thence to the sulfonic acid
(6) (Asahi and Yoshida, 1977).
An aqueous solution of unlabelled cartap hydrochloride was exposed
to sunlight for a period of 5 days. Analysis was by IR, UV and MS
methods. Three products were isolated after irradiation and the major
of these was identified as a polymer of nereistoxin (7) and represented 80% of applied dose. The polymer (7) was not toxic to fish (Oryzias latips).
Cartap was hydrolysed to nereistoxin (3) via dihydronereistoxin (2).
Nereistoxin (3) was converted into the polymer (7) probably after photolytic
formation of a nereistoxin diradical as shown in Scheme 1 (Obayashi
and Asaka, 1983).
Pesticide Type
Insecticide
