Chinomethionate

Description

Chinomethionate is a quinoxaline fungicide and acaricide introduced in 1968 to control powdery mildew and spider mites on fruits, ornamentals, cucurbits, cotton, coffee, tea, tobacco, walnuts, vegetables and glasshouse crops. It is nonsystemic, with contact activity only.

Chemical Properties

Chinomethionate is a tan to yellow crystals. Soluble in benzene, toluene, and dioxane; insoluble in water. It has been shown to have low toxicity to mammals, birds and bees, but is highly toxic to fish and some aquatic invertebrates.

Uses

Chinomethionat exhibits both acaricidal and fungicidal activities. It is a selective, non-systemic contact fungicide with both protective and eradicant control of powdery mildews on fruits, cucurbits, vegetables, ornamentals, tobacco and glasshouse crops.

Definition

ChEBI: A dithioloquinoxaline that results from the formal condensation of 6-methylquinoxaline-2,3-dithiol with phosgene. It has been used as a fungicide and acaricide for the control of mites and powdery mildew on citrus, vegetables, and walnuts, but is not appro ed for use in the EU.

General Description

Yellow crystals. Non-corrosive. Used as a selective fungicide.

Air & Water Reactions

Hydrolyzed in alkaline solution.

Reactivity Profile

A member of the quinoxaline, dithiolane family.

Hazard

Toxic by ingestion and inhalation.

Flammability and Explosibility

Not classified

Safety Profile

Moderately toxic by intraperitoneal, ingestion, and skin contact routes. A pesticide. When heated to decomposition it emits very toxic fumes of NOx and SOx.

Synthesis

Chinomethionate is synthesised from p-toluenamine as the starting material, via condensation of 6-methylquinoxaline-2,3-dithiol with phosgene, yielding a dithiol quinoxaline compound. The reaction formula is as follows:

Environmental Fate

Chemical/Physical. Reacts with ammonia forming 6-methyl-2,3-quinoxalinedithiol.

Metabolic pathway

Limited information is available to describe the degradation and metabolic fate of chinomethionat. Hydrolytic cleavage of the dithiocarbonate ring is the primary degradation reaction in water, plants and animals.

Degradation

Chinomethionat was degraded at pH 4,7 and 9 at 22 °C with DT₅₀ values of 10 days, 3.3 days and 3.6 hours, respectively. It is degraded under alkaline conditions to yield 6-methyl-2,3-quinoxalinedithiol (2) (PM) as shown in Scheme 1. Clark and Loeffler (1980) reported the extensive photodegradation of chinomethionat in benzene in a nitrogen atmosphere under UV light to yield dimeric condensation products and benzene insertion products.

Mode of action

Chinomethionate reacts with sulfur-containing amino acids in proteins, thereby disrupting the function of many enzymes and other proteins. Because there is no single target site, target site resistance is unlikely.

Pesticide Type

Fungicide; Acaricide; Miticide; Insecticide