Fenarimol

The Uses of Fenarimol

Fenarimol is a broad spectrum pyrimidine carbinol fungicide with protective, curative and eradicative activities against powdery mildew (Erysiphe spp., Pudusphaera leucutricha, Uncinula necatur, Sphaerutheca spp., Leveillula spp.) and scab (Venturia spp.) in many crops. It also controls powdery mildew (Sphaerutheca pannusa) in ornamentals and Fusarium patch (Micruduccium niuale), Take-all patch (Laefisaria fuciformis), Dollar spot (Sderutina humeucavpa) and red thread (Gaeumannumyces graminis) in turf and amenity grasses.

The Uses of Fenarimol

Plant fungicide.

The Uses of Fenarimol

Fenarimol is a pyrimidine based fungicide which acts against rusts, blackspot and mildew fungi and it works by inhibiting the fungus’s biosynthesis of important steroid molecules.

Definition

ChEBI: (2-chlorophenyl)(4-chlorophenyl)pyrimidin-5-ylmethanol is a member of the class of pyrimidines that is pyrimidin-5-ylmethanol in which one of the hydrogens attached to the carbon bearing the hydroxy group is replaced by a 2-chlorophenyl group while the other is replaced by a 4-chlorophenyl group. It is a tertiary alcohol, a member of monochlorobenzenes and a member of pyrimidines.

General Description

Pure white crystalline solid. Used as a fungicide. Irritates skin and mucous membranes.

Reactivity Profile

Fenarimol produces toxic gases when heated to decomposition.

Safety Profile

Moderately toxic by ingestion. Experimental reproductive effects. Mutation data reported. When heated to decomposition it emits toxic fumes of Cland NOx.

Metabolic pathway

The primary dissipation mechanism of fenarimol in the environment involves photolysis on plants/soil surfaces and water. More than 80 photoproducts have been observed, resulting from the reduction of the pyrimidine ring, hydrolysis, ring migration and cleavage of the phenyl and pyrimidine ring moieties. Under laboratory conditions in the dark, fenarimol is relatively persistent in soil, but a more rapid dissipation was observed under field conditions with DT₅₀ values of 18-140 days, attributed to photolysis of fenarimol on the soil surface. Fenarimol degrades in/on plant foliage/fruit surfaces mainly by photochemical processes. In animals, fenarimol is metabolised extensively to yield hydroxylated, cleavage and dechlorination products. The primary photolytic and metabolic pathways of fenarimol are presented in Schemes 1 and 2.

Degradation

Fenarimol(1) is stable in sterile buffered water in the dark at pH 3,6 and 9 at 25 °C, 37 °C and 52 °C for 28 days (Decker and Sullivan, 1975) but is readily degraded via photolysis. The photolytic DT₅₀ in distilled water under natural sunlight and clear sky conditions at 40°N in mid-summer was approximately 12 hours (Day, 1975). The primary aqueous photolysis reaction involved the migration of the pyrimidine ring to one of the chlorophenyl rings, followed by the oxidation of the carbinol moiety to the corresponding ketone to yield 4-chloro-2-(5-pyrimidyl)-2'-chlorobenzophenone (2).
Fenarimol was extensively photodegraded on solid surfaces. More than 80 photodegradation products were formed when fenarimol was exposed to sunlight on a stainless steel surface for up to 200 hours (Althaus and Bewley, 1978a). All photoproducts were formed at very low levels (less than 3% each) and 14 were identified. An abbreviated photogradation pathway of fenarimol is presented in Scheme 1. These products were generated from the following reactions: the migration of the pyrimidine ring to one of the chlorophenyl rings, followed by the oxidation of the carbinol moiety to yield compound 2; cleavage of either one of the chlorophenyl (to yield 3,4) or pyrimidine rings (5,6); aryl hydroxylation of one of the chlorophenyl rings (7); carbinol dehydroxylation reaction to yield 8 and a bridged fluorene product (9) from the dechlorination reaction. Various cleavage products (carboxylic acids) derived from the chlorophenyl (10-13) and the pyrimidine moieties (14) were also observed.