alphamethrin mukesh research paper

This article was downloaded by:[Florida State University Libraries]
On: 15 April 2008
Access Details: [subscription number 789349894]
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Environmental Science
and Health, Part B
Pesticides, Food Contaminants, and Agricultural
Wastes
Publication details, including instructions for authors and subscription information:
http://www.informaworld.com/smpp/title~content=t713597269
Phototransformation of Alphacypermethrin as Thin Film
on Glass and Soil Surface
Mukesh Kumar Raikwar a
; Subir Kumar Nag a
a
Plant Animal Relationship Division, Indian Grassland and Fodder Research
Institute, U.P., India
Online Publication Date: 01 September 2006
To cite this Article: Raikwar, Mukesh Kumar and Nag, Subir Kumar (2006)
'Phototransformation of Alphacypermethrin as Thin Film on Glass and Soil Surface ', Journal of Environmental Science
and Health, Part B, 41:6, 973 - 988
To link to this article: DOI: 10.1080/03601230600806186
URL: http://dx.doi.org/10.1080/03601230600806186
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf
This article maybe used for research, teaching and private study purposes. Any substantial or systematic reproduction,
re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly
forbidden.
The publisher does not give any warranty express or implied or make any representation that the contents will be
complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be
independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings,
demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or
arising out of the use of this material.

DownloadedBy:[FloridaStateUniversityLibraries]At:14:1715April2008
Journal of Environmental Science and Health Part B, 41:973–988, 2006
Copyright C Taylor & Francis Group, LLC
ISSN: 0360-1234 (Print); 1532-4109 (Online)
DOI: 10.1080/03601230600806186
Phototransformation
of Alphacypermethrin as Thin
Film on Glass and Soil Surface*
Mukesh Kumar Raikwar and Subir Kumar Nag
Plant Animal Relationship Division, Indian Grassland and Fodder Research Institute,
U.P., India
Photodegradation of alphacypermethrin ((RS)-α cyano-3-phenoxy benzyl (1RS) cis-3-
(2,2,dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate) was studied as a thin film on
glass surface and on black and red soil surfaces. A number of photoproducts from glass
surfaces have been isolated, characterized and identified by gas chromatography-mass
spectroscopy (GC-MS). However, only two of them viz. 3-phenoxy benzyl alcohol and
[2,2-dichlorovinyl-3(2,2,dimethyl) cyclopropane carboxylate] could be identified from
both the soil. Rate of photodegradation on glass and soil surface under UV and
sunlight followed first order kinetics with significant correlation coefficients. The rate
of photodegradation was greater on black than on red soil.
KeyWords: Photodegradation; Black soil; Red soil; UV; Sunlight; Alphacypermethrin.
INTRODUCTION
Alphacypermethrin (1R cis, αS and 1S cis αR enantiomeric pair of
α-cyano-3-phenoxy benzyl-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane
carboxylate) is a synthetic pyrethroid insecticide having a broad spectrum
of activity. It is a stereo selective compound consisting of the mixture of
four stereoisomers owing to the presence of two chiral carbon atoms. The
stereo selectivity of alphacypermethrin is very high. It is effective against
a wide range of insect pests of agricultural importance, particularly of
Lepidoptera & Coleoptera order, in different crops at a very small dose
of 5–30 g a.i./ha.[1]
It is also used to protect seeds during storage, to
eradicate vectors of endemic diseases like malaria, and to fight household
insects.[2–4]
Its persistence and residues have been evaluated only on a few
∗
A part of Ph.D. thesis of the first author in the Department of Chemistry submitted to
the Bundelkhand University, Jhansi, U.P., India.
Address correspondence to Subir Kumar Nag, Senior Scientist, PAR Division, IGFRI,
Jhansi-284003, U.P., India. E-mail: subirknag@yahoo.com or nagsk 67@rediffmail.com
973

974 Raikwar and Nag
crops in Indian condition.[5–8]
From the view point of environmental safety
the metabolism of cypermethrin [(RS)-α-cyano-3-phenoxybenzyl (1RS)-Cis,
trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate] has been
studied in mammals,[9–11]
soils[12–14]
and plants.[8,15,16]
The photodegradation
of cypermethrin studied by Takahashi et al.[17]
in water and on soil surfaces
revealed that both cis and trans isomers rapidly degraded on soil with initial
half-life of 0.6–1.9 days. The main reactions involved in degradation were
cleavage of ester or diphenyl ether linkage, oxidation of –CHO, hydration of
–CN, oxidative cleavage, dehalogenation etc. As little published literature
about photodegradation of alphacypermethrin was available, the present
experiment was conducted to see the rate of photolysis and the nature of
photoproducts of alphacypermethrin formed when irradiated as thin film on
glass and soil surfaces under ultra-violet light (UV) and sunlight.
MATERIAL AND METHODS
Chemicals
Technical grade (99%) alphacypermethrin was obtained by courtsey of
M/s. Meghamani Organics Ltd. Ahmedabad, India. It was further purified by
repeated crystallization from hexane. The purity of the compound was checked
by m.p. (80◦
C), thin layer chromatography (solvent system, hexane: acetone
2:1 v/v, Rf 0.57) and gas liquid chromatography.
Solvents and Reagents
All the solvents used in the experiment were Laboratory Grade Regents
(LR) or commercial grade. Hexane was distilled over anhydrous sodium sulfate
in the boiling range 60–80◦
C before use. Acetone was refluxed over KMnO4 and
then distilled.
Soil Characteristics
Two types, black soil and red soil, were used in the experiment. Their
properties are given in Table 1.
Chromatography
Gas Liquid Chromatography (GLC)
Alphacypermethrin degradation rates were determined using a PC based
gas liquid chromatograph (Varian CP–3800) equipped with an electron capture
detector (ECD, Ni63
) and a capillary column (CP SIL 5CB, 30 m × 0.53 mm i.d.

Phototransformation of Alphacypermethrin 975
Table 1: Physicochemical properties of the soils used in the experiment.
Soil properties Black soil Red soil
pH (1:2.5) 7.62 6.72
EC (1:2.5) 0.87 dSm−1
0.76 dSm−1
Organic carbon 0.6 0.47
Soil order Inceptisol Alfisol
Particle size analysis
Silt (%) 49.5 30.0
Clay (%) 27.2 28.3
Sand (%) 23.3 41.7
Soil Texture Loam Clay loam
Available Nitrogen (Kg/ha) 288.24 185.02
Available P2O5(Kg/ha) 22.27 12.23
Available K2O (Kg/ha) 476 280
× 0.25 mm film thickness). The operating conditions were as follows: Column
temperature: 250◦
C for 1 min, then 5◦
C/min up to 280◦
C (5 min), Injection
port temperature: 280◦
C, Detector temperature: 300◦
C. Nitrogen was used as
the carrier gas with the flow rate of 1 mL/mins. through column and make up
30 mL/min.
Thin Layer Chromatography (TLC)
Thin layer chromatography plates were prepared by spreading a slurry of
silica gel G containing 10% gypsum (as binder) in water on 5 cm × 20 cm and
20 cm × 20 cm plates, maintaining a uniform thickness of 0.25 mm using a
TLC applicator. The mobile phase used for TLC were hexane + acetone (2:1,
4:1, 9:1 v/v), with iodine vapour used as the chromogenic reagent.
Column Chromatography (CC)
Photoproducts were separated by column chromatography (CC) using a
glass column of 75 cm × 2 cm id containing 500 g of 60–100 mesh silica gel for
column chromatography (preactivated at 120◦
C) in hexane. The column was
successively eluted with hexane, hexane and toluene and toluene and acetone
in different proportions. Different fractions (25 mL) were collected and distilled
on a rotary vacuum evaporator. The fractions containing same product were
combined and purified further.
Preparative TLC
Single or mixtures of a few compounds of different polarity, obtained earlier
through column chromatography, were spotted in 20 × 20 cm plates coated
with silica gel G and run in a suitable solvent system as mentioned above.
After running of plates and visualization, spots appearing at the same position
(i.e. same Rf value) were marked, scratched along with the coated silica gel

976 Raikwar and Nag
and put in a small conical flask. They were dissolved in a small quantity of
acetone, filtered and concentrated to get the pure isolated compound. A number
of plates was used to get the whole quantity obtained from the column isolated
and/or separated.
Spectroscopy
The ultraviolet and visible (UV-VIS) spectrum of alphacypermethrin was
recorded on a Perkin-Elmer Lambda UV/VIS spectrophotometer in methanol
and water, using a quartz cuvette (1 cm path length).
Gas Chromatography–Mass Spectroscopy (GC-MS)
The GC-MS spectra were performed on Fison gas chromatograph (trace
GC) connected with an electron impact mass detector (MD–800) and fitted with
a capillary Column (BD-17, J&W Scientific, 30 m × 0.32 mm i.d.× 0.25 µm
film). The conditions were as follows. Injection port temperature: 260◦
C (Split
1:10); Oven temperature: 150–250◦
C, 2◦
C/min, Helium was used as the carrier
gas.
Photolysis on Glass Surface
For studies on glass surface, a solution of alphacypermethrin in hexane (10
mL, 1000 mg/L) was applied uniformly on petriplates (20 cm diameter). The
solvent was allowed to evaporate off at room temperature leaving behind a thin
layer of alphacypermethrin on the surface of the petriplates which were then
exposed to UV light by placing them under the ultraviolet lamp (λ-254 nm) at
a distance of 30 cm for one hour. The temperature at the test surface varied
from 25–30◦
C. A set of petriplates was also exposed to sunlight in the months
of April-May for 7–8 hours (9.30 AM–5.30 PM). The temperature at the test
surface varied from 30–40◦
C. Sunlight intensity at wavelength between 300
and 400 nm was approximately 720, 780 and 350 m Wcm−2
at the beginning,
middle and end of the day, respectively.
To get a sufficient quantity of photoproducts a number of plates were
irradiated. After irradiation the plates were extracted with hexane (5 × 5 mL).
The combined hexane extracts from different plates were concentrated at a
low temperature under vacuum. Photoproducts thus formed were separated
by column chromatography, purified by preparative TLC, recrystallisation and
subsequently identified by GC-MS.
Photolysis on Soil Surface
Soil samples collected from the Central Research Farm of the Institute
were dried in air under shade. They were pulverized and passed through a
2 mm sieve. Soils were also sterilized in an autoclave for two hours at a

temperature of 121◦
C and pressure of 15 lb/sq inch. A slurry of soil (50 g)
was made with double distilled water and sprayed uniformly on to petri plates
(20 cm dia.) to give a layer of 2 mm thickness which was then dried in air.
Alphacypermethrin in hexane (10 ml, 1 mg/ml) was applied uniformly to the
surface of the soil using a pipette. The plates were again dried in air and
then irradiated under UV light for four hours and under sunlight for 18–
20 hours. After irradiation the soil was removed from the plates and extracted
with hexane (5 × 5 mL). The extracts from several plates were combined and
concentrated at low temperature. Photoproducts thus formed were separated
by column chromatography, preparative TLC and identiﬁed by GC-MS.
Rate of Photodegradation of Alphacypermethrin
on Glass Surface
A solution of alphacypermethrin (1 mL of 10 mg/L) in hexane was
uniformly applied on petriplates of 5 cm diameter, with a pipette. The solvent
from the petriplates was evaporated off at room temperature leaving behind
a thin ﬁlm of alphacypermethrin. Plates were exposed to UV Light (λ-254
nm) at a distance of 30 cm and also to sunlight for different durations. One
set of petriplates were covered with aluminum foil and kept in the dark as
control. Sample plates were withdrawn from the light source at random (three
replicates) at different intervals. Samples irradiated under UV light were
withdrawn at 0, 5, 10, 20, 30, 45 and 60 mins and those from sunlight were
withdrawn at 0, 15, 30, 45, 75, 90, 105 and 120 mins. The content of each
petriplate was extracted thoroughly with hexane (5 × 3 mL). The solvent was
evaporated to dryness and residues were diluted with hexane (1 mL) for GLC
analysis.
Rate of Photodegradation of Alphacypermethrin on Soil Surface
The rate of photodegradation of alphacypermethrin was studied on black
and red soil. Soil passed through a 2 mm sieve was suspended in distilled
water (1 g in 2 mL) and the suspension was used to prepare a thin layer on
the bottom of a petriplate (5 cm dia). Air drying of the plates resulted in a thin
uniform layer of soil on the glass surface. A solution of alphacypermethrin (10
mg/L, 1 mL) was uniformly applied on the petri plates and the solvent was
allowed to evaporate at room temperature. The plates were exposed to UV
light and sunlight for different durations. In case of UV irradiation, samples
were withdrawn at random in triplicate at intervals of 0, 30, 60, 90, 120, 150
and 180 mins (black soil) and 0, 30, 60, 90, 120, 180, 240 and 300 mins (red
soil). Samples irradiated under sunlight were withdrawn at 0, 1, 2, 3, 4, 5, 6
and 7 days (black soil) and 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 days (red soil).
After irradiation, soil was scraped from each plate and extracted with hexane

978 Raikwar and Nag
(5 × 3 mL). The combined extracts were then centrifuged. The supernatant
was then concentrated to 1 mL at a low temperature and analysed in GLC.
RESULTS
Rate of Photodegradation of Alphacypermethrin
The rate of photodegradation of alphacypermethrin was studied on a glass
surface and also on black and red soil surface under UV light as well as under
sunlight. Results showed that no degradation of alphacypermethrin occurred
in the dark, since more than 90 percent of the applied alphacypermethrin was
recovered unchanged during the time frame of the study which indicated that
alphacypermethrin was stable under these conditions and the degradation
observed in the study to the samples can be attributed to photolysis only.
The rate of photodegradation followed first order kinetics with significant
correlation coefficients (Figs. 1–4). The rate constant and half-life values are
given in Table 2.
Isolation and Identification of Photoproducts Formed
on Glass Surface
The UV spectrum of alphacypermethrin in methanol and water exhibited
bands at 245.6 nm ( = 24,560) for the allowed π-π∗
transition of the phenyl
rings and a band at 276 nm ( = 27,600), which is essentially n-π∗
in character
resulting from the combined transition of the carbonyl group and the lower
energy bond of the aromatic rings. These π-π∗
and n-π∗
transition can lead
to the production of either singlet or triplet excited states. So no unique
excited state can be invoked to explain the variety of photochemical reactions
Figure 1: Linear plot for first order kinetics of alphacypermethrin as thin film on glass surface
under ultraviolet light.

Figure 2: Linear plot for first order kinetics of alphacypermethrin as thin film on glass surface
under sunlight.
under gone by various functional groups of alphacypermethrin. The possible
photodegradation products of alphacypermethrin as thin film on glass surface
under UV light is shown in Figure 5.
Elution of column with hexane (fraction I–V) gave a viscous liquid, which
was further purified by preparative TLC (solvent system, hexane: acetone
Figure 3: Linear plot for first order kinetics of alphacypermethrin as thin film on black and red
soil under Ultraviolet light.

980 Raikwar and Nag
Figure 4: Linear plot for first order kinetics of alphacypermethrin as thin film on black and red
soil under sunlight.
9:1, Rf 0.65). The compound was eluted at 17.35 mins and gave a parent ion
peak at m/z 209, which was also the base peak, with fragment ion peaks at
183 (M+
-CN), 169 (M+
-CH2CN), 141, 133, 116 on the basis of which it was
identified as 2-(3 phenoxy)-benzyl cyanide (II). Further elution of column with
hexane and toluene (7:3 v/v, fractions I–VI) and distillation of the eluate gave
pale yellow viscous oil, which was further purified by short path distillation
under reduced pressure (120◦
C bath temperature). On TLC it gave a single
spot (solvent system hexane: acetone 9:1, Rf 0.51). It eluted at 14.83 mins and
Table 2: Rate constants and half-life values for alphacypermethrin on glass and
different soil surface under UV and sunlight.
Surface Source of irradiation Rate constant (k) Half-life R2
Glass UV 0.0486 min−1
14.26 min 0.95
Glass Sunlight 0.0191 min−1
36.26 min 0.95
Black soil UV 0.0122 min−1
56.8 min 0.98
Black soil Sunlight 0.3084 day−1
2.24 d 0.96
Red soil UV 0.0073 min−1
94.07 min 0.99
Red soil Sunlight 0.2181 day−1
3.17 d 0.99

Figure 5: Possible photodegradation products of alphacypermethrin on thin film on solid
surface under ultraviolet light.
gave a molecular ion peak at m/z 198 with the base peak at m/z 197 (M+
-1)
and a fragment peak m/z 169 (M+
-CHO), 141 (M+
-CHOCO), 115, 77 and on
the basis of it the compound was identified as 3-phenoxy-benzaldehyde (III).
Elution of column with toluene (fraction I–V) gave colorless viscous liquid
which was further purified by preparative TLC (solvent system hexane:
acetone 8.5: 1.5, Rf 0.73, It eluted at 8.89 mins and gave a parent ion peak
at m/z 225 with base peak at m/z 198 (M+
-HCN) and fragment ion peaks
at m/z 182 (M+ –
CNOH), 169, 141, 77, 55. The compound was identified as
α-cyano–3–phenoxy benzyl alcohol (IV).
Elution of column with toluene and acetone (99:1, v/v, fraction I–VII) gave a
solid, purified by preparative TLC (solvent system hexane: acetone 8.5: 1.5, Rf.
0.56). It eluted at 51.74 mins and gave the molecular ion peak at m/z 208 (M+
)
indicating the presence of chlorine atom. The fragment ion peaks appeared at

982 Raikwar and Nag
191 (M+
-OH), 180 (M+
-CO), 163, 140, 128, 123, 107 indicating the presence
of the chlorine atom. It was identified as 3-(2, 2–dichlorovinyl)-2, 2-dimethyl-
cyclopropane carboxylic acid (V).
Further elution of the column with toluene and acetone (98:2 v/v, fraction
I–VI) gave a white crystalline solid, which was further purified by preparative
TLC (solvent system, hexane: acetone 8:2, Rf 0.62). The compound was eluted
at 55.49 mins, showed the molecular ion peak at m/z 391 and other fragment
ion peaks at 315 (M+
-C6H5), 298, 207, 191, 183, 169, 123, 107. It was identified
as 3-phenoxy benzyl–3-(2, 2-dichlorovinyl)-2, 2-dimethyl cyclopropane carboxy-
late (VI).
Figure 6: Proposed photochemical pathways to accounts for the observed photoproducts.

Next few fractions (VI–XII) of the column eluted with toluene and acetone
(98:2 v/v) gave solid substance, puriﬁed by preparative TLC. The compound
was eluted at 16.05 mins. The mass spectrum of the compound showed
molecular ion peak at m/z 435 (M+
) and other fragment ion peaks at 391

984 Raikwar and Nag
(M+
-COO), 356, 207, 183, 169, 163, 127, 77, 51. The compound was identified as
α-carboxy-3phenoxybenzyl-3-(2,2-dichlororvinyl)-2, 2 dimethyl cyclopropane
carboxylate (VII).
Further elution of the column with toluene and acetone (97:3 v/v, fractions
I–V) gave a yellow liquid, purified by preparative TLC (solvent system hexane:
acetone 7.5: 2.5, Rf 0.48). The compound showed molecular ion peak at m/z
371(M+
) and eluted at 14.98 mins. The mass spectrum indicated the presence
of chlorine atom and fragment ions appeared at 300 (M+
-2Cl), 208, 169, 163,
127, 91, 77, 51. The compound was identified as 1-(α-cyano-3-phenoxy) benzyl-
3(2,2-dichlorovinyl)-2,2-dimethylcyclopropane (VIII).
I–IV) gave a colorless solid substance, purified by preparative TLC. The
compound was eluted at 59.55 mins and gave the molecular ion peak at m/z
381(M+
). The mass spectrum indicated the presence of chlorine atom. The
fragments appeared at 346 (M+
-Cl), 305 (M+
-C6H5), 298, 288, 227, 208, 173,
140, 129, 115. The compound was identified as α-cyano-3-phenoxy benzyl-3(2-
chloro vinyl)-2, 2-dimethyl cyclopropane carboxylate (IX).
I–V) yielded a compound, purified by preparative TLC. The compound was
eluted at 29.00 mins. and gave the molecular ion peak at m/z 339 (M+
) and
other fragments at 295 (M+
-COO), 269 (M+
-2Cl), 261, 245, 227, 207, 191, 149,
123, 107. It was identified as α-cyano-3-hydroxy benzyl 3-(2, 2-dichlorovinyl)-
2,2-dimethyl cyclopropane carboxylate (X).
Elution of the column with toluene and acetone (94:6 v/v, fractions I–III)
gave a yellowish liquid, which was further purified by preparative TLC. The
compound was eluted at 12.88 mins. and gave the molecular ion peak at m/z
223 (M+
) and others at 197 (M+
-CN), 169 (M+
-COCN), 149, 132, 123, 105, 77,
65 and identified as 3-phenoxy benzoyl cyanide (XI).
A few more compounds were also obtained as a result of photo irradiation
of alphacypermethrin under UV Light. However those compounds could not
be separated from the mixture through column chromatography. They were
identified in the mixture by GC-MS.
Photoproduct XII eluted at 9.42 mins and showed molecular ion peak at
m/z 200 (M+
) with base peak at 198 (M+
-2H) due to 3-phenoxy benzaldehyde,
169(M+
- CH2OH) due to formation of phenoxy phenyl cation, 141 due to C6H5-
C5H4
+
. From the mass fragmentation the compound was tentatively identified
on 3-phenoxy benzyl alcohol (XII).
Photoproduct XIII was eluted at 13.97 mins. Its mass spectrum showed
molecular ion peak at m/z 366 (M+
). Different mass fragments appeared at
m/z 183, 169, and 141. On the basis of molecular ion and mass fragmentation
pattern the molecule was tentatively identified as 1, 2-bis- (3-phenoxy phenyl)
ethane (XIII).

The mass spectrum of photoproduct XIV (Rt 25.369 min) showed molecular
ion peak at m/z 327 (M+
+1). Different mass fragments of the compound came
at 291, 256, 221, 190, 156, 163 and 129. The mass spectrum indicated the
presence of chlorine atoms in the molecule. On the basis of the mass spectrum
the compound was tentatively identified as bis-3 (2, 2-dichloro)-2, 2-dimethyl
cyclopropane (XIV).
Photoproduct (XV) was eluted at 72.44 mins and gave the molecular ion
peak at m/z 273. Different mass fragments of the photoproduct appeared at
m/z 246 (M+
- CH2·CH), 229 (M+
- CONH2), 202, 185, 151, 135 (base peak)
attributed to phenyl acetamide, 123, 111 and 107. On the basis of this
information the compound was tentatively identified as α-carbomoyl benzyl-
3-vinyl-2, 2-dimethyl cyclopropane carboxylate (XV).
The same compounds were also identified after sunlight irradiation of
alphacypermethrin. However, the rate of formation of these photoproducts was
slow a under sunlight than under UV light.
Identification of Photoproducts Formed on Soil Surface
Compounds III and V were detected in both types of soil i.e. black and red
soil under both UV and sunlight irradiation.
DISCUSSION
Photolysis on Glass and Soil Surface
The identification of photoproducts of alphacypermethrin formed as thin
film on glass surface can be rationalized as originating from any one of
the following photochemical processes like cleavage of ester linkage, cleav-
age of diphenyl ether linkage, hydration of CN group to CONH2 group,
hydrolysis of CONH2 group to COOH group, dehaloganation, decarboxylation,
self-coupling of fragment radicals, oxidation etc (Fig. 2). The photochemical
cleavage via pathway A involves bond breaking between carbonyl carbon and
oxygen atom of the ester group (Ia) leading to formation of two radicals
which can subsequently form product V [2,2-dichlorovinyl-3 (2,2-dimethyl)-
cyclopropane carboxylate] and IV (α-cyano-3-phenoxy benzyl alcohol). Product
III (3-phenoxy benzaldehyde) is formed by removal of HCN from photoproduct
IV. Photoproduct III is then reduced to give photoproduct XII (3-phenoxybenzyl
alcohol). Product III and V were also formed in both black and red soils under
both UV and sunlight.
Pathway B involved cleavage of ester oxygen and benzylic carbon bond
yielding (Ib). The discrete radical intermediate thus produced by scission
of the bond abstracts proton to yield photoproduct II [2(3-phenoxy)-benzyl
cyanide]. Self-coupling of the radicals following the removal of CN group,

986 Raikwar and Nag
on the other hand, resulted in the formation of product XIII [1,2-bis-3-
phenoxy phenyl ethane]. Photoproduct VIII [α-cyano-3-phenoxy benzyl-3(2,2-
dichlorovinyl)-2,2-dimethyl cyclopropane], which may also be called as de-
carboxylated alphacypermethrin, was formed from the intermediate Ib by
the loss of carbon dioxide via photo-induced decarboxylation. This involved
simple coupling of the discrete free radicals after loss of carbon dioxide from
intermediate Ib. Pathway A and B are the most important and dominant
photoreaction mechanisms of all ester group pyrethroids. Products II, III, IV
and V also obtained in photo and other degradation studies of cypermethrin
and other related pyrethroids.[16–21]
In pathway C intermediate Ic is formed by scission of diphenylether
linkage. Subsequent abstraction of proton from the medium resulted in the for-
mation of the photoproduct X [α-cyano-3-hydroxybenzyl-3(2,2-dichlorovinyl)-
2,2-dimethyl cyclopropane carboxylate]. Similar cleavage of diphenyl ether
linkage i.e. bond between phenyl ring attached is benzylic carbon atom and
ether oxygen result in the formation of intermediate stage Id (Pathway D).
The resultant fragment radical on abstraction of proton followed by photo
dehalogenation of vicinal dihalides by extrusion of two halogen atoms and
hydration of the CN group gave the product XV (α-carbomoyl benzyl-3-vinyl-2,
2-dimethyl cyclopropane carboxylate).
Photodehalogenation of I caused by homolytic cleavage of carbon-halogen
bond following n-σ∗
excitation yielded the photoproduct IX [α-cyano-3-phenoxy-
benzyl-3-(2-chlorovinyl)-2,2-dimethyl cyclopropane]. Reductive dehalogenation
is an important photochemical reaction and degradation mechanism and was
observed in case of other synthetic pyrethroids also.[17]
Hydration of CN group in 1 formed the carbamoyl derivative which
on hydrolysis gave the product VII [α-carboxy-3-phenoxy benzyl-3-(2,2-
dichlorovinyl)-2, 2-dimethylcyclopropane carboxylate]. On photo induced
decarboxylation of VII product VI [3-phenoxy benzyl-3-(2,2-dichlorovinyl)-2,
2-dimethyl cyclopropane carboxylate] was formed.
Cleavage of carbonyl carbon and C-1 of cyclopropane ring by homolytic
ﬁssion and subsequent self-coupling of the discrete radical intermediates
thus produced formed the product XIV [bis-3 (2,2-dichloro)-2, 2-dimethyl
cyclopropane].
Rate of Photodegradation
The rate of photodegradation was greater on glass than on soil surface.
This may be due to the fact that some pesticides get adsorbed on soil clays and
other colloidal substances and so become less available to light. The rate of
degradation was higher on black soil than red soil under both UV and sunlight
(Table 2). This may be due to difference in organic matter content and pH of
the soil (Table 1).

CONCLUSION
Irradiation of alphacypermethrin as a thin ﬁlm on glass surface under UV
and sunlight has given basic information about photoreactivity, photoproducts
and possible chemical pathways in the environment. Although, number of
photoproducts were formed on the glass surface, only two major products
could be identiﬁed in the soil surface. Hydrolysis of ester bond, cleavage of
diphenyl ether bond, dehalogenation, decarboxylation and hydration of CN
groups are some of the major process of formation of different products. It
may be concluded that in the environment there will be rapid breakdown of
alphacypermethrin on glass and also on soil surface.
ACKNOWLEDGMENT
The authors are grateful to the Head, PAR Division and the Director,
Indian Grassland and Fodder Research Institute, Jhansi, Uttar Pradesh,
India for providing necessary facilities to carry out the experiment, constant
encouragement and valuable suggestions.
REFERENCES
1. Anonymous. The Pesticide Manual A World Compendium, 8th edition. The British
Crop Protection Council (Editor-Charles R. Worthing) 1987; 3690–3692.
2. Demoute, J.P. A brief review of the environmental fate and metabolism by
pyrethroids. Pestic. Sci. 1989, 27, 375–385.
3. Hirano, M. Characteristic of pyrethroids for insect pest control in agriculture.
Pestic. Sci. 1989, 29, 353–360.
4. Gupta, P.K.; Bhumi, K.A. In Pyrethroids: their use in the control of animal
ectoparasites and impact on environment health; Gupta, P.K.; Ravi Prakash, V., Eds.;
Jagmandir Book Agency: New Delhi, India, 1988; 71–80.
5. Barooah, A.K.; Borthakur, M.C. Residues of alphacypermethrin in tea and its
potential daily intake. Pestic. Res. J. 1994, 6 (2), 161–166.
6. Tamilselva, C. Residues of alphacypermethrin and its metabolites in cotton. Indian
J. Environmental Toxicology 1995, 5, 71–72.
7. Pandit, G.K.; Bhattacharya, A.; Bose, A.K.; Bandyopadhyay, D.; Das, A.K.; Adity-
achaudhury, N. Persistence of alpha-cypermethrin in cabbage and monocrotophos in
three soils of West Bengal. Pestic. Res. J. 1996, 8 (2), 132–138.
8. Kumar, R.; Dixit, A.K. Study on the metabolism of alphacypermethrin, a pyrethroid
insecticide in mustard (Brassica camperstris Linn). Pestic. Res. J. 2002, 14 (2), 313–
318.
9. Hutson, D.H.; Gaughan, L.C.; Casida, J.E. Metabolism of cis and trans isomers of
cypermethrin in mice. Pestic. Sci. 1981, 12, 385–398.
10. Crawford, M.S.; Croucher, A.; Hutson, D.H. The metabolism of pyrethroid insecti-
cide cypermethrin in rats; excreted metabolites. Pestic. Sci. 1981, 12, 399–411.

988 Raikwar and Nag
11. Cole, L.M.; Ruzo, L.O.; Wood, E.J.; Casida, J.E. Pyrethroid metabolism: Compara-
tive fate in rats of tralomethrin, tralocythrin, deltamethrin and (1RS)-cis cypermethrin.
J. Agric. Food Chem. 1982, 30, 631–636.
12. Roberts, T.R.; Standen, M.E. Degradation of the pyrethroid cypermethrin, NRDC
149 and the respective Cis-(NRDC-160) and trans-(NRDC-159) isomers in soils. Pestic.
Sci. 1977, 8, 305–319.
13. Roberts, T.R.; Standen, M.E. Further studies of the degradation of pyrethroid
insecticide cypermethrin in soils. Pestic. Sci. 1981, 12, 285–296.
14. Sakata, S.; Mikami, N.; Matsuda, T.; Miyamoto, J. Degradation and leaching
behaviour of the pyrethroid insecticide cypermethrin in soils. J. Pestic. Sci. 1986, 11,
71–79.
15. Wright, A.N.; Roberts, T.R.; Dutton, A.J.; Doig, M.V. The metabolism of cyperme-
thrin in plants: the conjugation of cyclopropyl moiety. Pestic. Biochem. Physiol. 1980,
13, 71–80.
16. Furuzawa, K.; Nobuyoshi, M.; Yamada, H.; Miyamoto, J. Metabolism of
pyrethroids insecticide cypermethirn in cabbage. J. Pestic. Sci. 1986, 11, 253–260.
17. Takahashi, N.; Mikami, N.; Matsuda, T.; Miyamato, J. Photodegradation of the
pyrethroid insecticide cypermethrin in water, soil and plant foliage. Pestic. Sci. 1985a,
16, 119–131.
18. Ueda, K.; Loretta, C.; Gaughan, L.C.; Casida, J.E. Photochemistry of the
resmethrin and related pyrethroids. J. Agric. Food Chem. 1974, 22 (2), 212–220.
19. Mikami, N.; Takahashi, N.; Hayashi, K.; Miymato, J. Photodegradation of fen-
valerate in water and on soil surface. J. Pestic. Sci. 1980, 5, 225.
20. Chattopadhyaya, S.; Dureja, P. Photolysis of ﬂucythrinate. Pestic. Sci. 1991, 31,
163–173.
21. Katagi, T. Photodegradation of the pyrethroids insecticide Esfenvelarate on soil,
clay, minerals and humic acid surface. J. Agric. Food Chem. 1991, 39, 1351–1358.

alphamethrin mukesh research paper

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to alphamethrin mukesh research paper

Similar to alphamethrin mukesh research paper (20)

More from Dr. Mukesh Raikwar

More from Dr. Mukesh Raikwar (10)

alphamethrin mukesh research paper