Degradation of Pesticides - Pesticides: Evaluation of Environmental Pollution - page 60

O

O

H
R

O

Cl Cl Cl O

O

C

O

Cl C C

NC C

Cl C

uv C

O O O

O

C

Cl CN Cl C C

Cl C

R

R

H

R

Cl R Cl

H H

Cl

H

Imidacloprid : Imidacloprid, 1-(6-chloro-3-pyridylmethyl) N-Nitroimidazolidin-2-ylideneamine,
an insecticide, on photodegradation (λ ~ 254 nm) in water, produces the following compounds
which might be formed via the bond cleavage of N-NO 2 to imine (=NH), followed by oxidation.

O

NH NH

CH 2 N N

CH 2

uv

N-NO 2 NH

uv

Cl Cl

N N

COOH

NH

N

CH 2

O

Cl

N

Cl

N

2,4-D : 2,4-Dichlorophenoxy acetic acid, a weedicide, on photodegradation by UV irradia-
tion, undergoes degradation as

OCH 2 COOH

Cl

Cl

•

CH 2 OH COOH

OH

OH

Cl

•

Cl

OH

Cl

Esters + Carboxylic acid
Aliphatic alcohol

(OH) n

Cl

3.3.2 Photodegradation of Organophosphate Pesticides

Most organophosphorus pesticides have the following general formula.

O or S

RO

P

RO

X

where X is aliphatic, homocyclic, or heterocyclic groups; R is alkyl group.
Organophosphorus pesticides undergo photochemical degradation mainly by ester
cleavage, reduction, oxidation of thio-ether group, isomerization, dehalogenation, dehy-
drohalogenation, dealkylation, cyclization, dimerization, etc.