This slide is my MS presentation on the course (Chem524F) of Agrochemicals.

1. Agrochemicals &
Pesticides
WELCOME TODAY..
MD: AHAD ALI
ORGANIC CHEMISTRY
UNIVERSITY OF RAJSHAHI
RAJSHAHI-6205, BANGLADESH

2. Pest & Pesticides
Pest:
An insect or small animal that is harmful or that damages plants, food,
and other crops.
Pesticides:
In general, a pesticide is a chemical or biological agent (such as a virus,
bacterium or disinfectant) that deters (Discourage), incapacitates
(injuries), or kills the pests. The term pesticide includes herbicide,
insecticide, nematicide, molluscicide, avicide, rodenticide, bactericide,
fungicide, growth regulator etc.
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3. Classifications
Example; herbicides,
insecticides
Target organism
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Chemical structure
Examples: organic,
inorganic, synthetic.
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Physical state
Examples: gaseous
03
Plant - derived pesticides
Examples: pyrethroids,
rotenoids, nicotinoids.
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4. Organochlorinated
Pesticides
Organochlorine (OC) pesticides are synthetic pesticides widely
used all over the world. They belong to the group of chlorinated
hydrocarbon derivatives, which have vast application in the
chemical industry and in agriculture. These compounds are
known for their high toxicity, slow degradation and
bioaccumulation.2 Representative compounds in this group
include DDT, methoxychlor, dieldrin, chlordane, toxaphene, and
benzene hexachloride

5. Action Mechanism of
Organochlorinated Pesticides
➢ The OP group of pesticides asserts its
effects through irreversible inactivation of
the enzyme acetylcholinesterase, which is
essential for nerve function in humans,
insects and many other animals. OP
samples degrade rapidly by hydrolysis on
exposure to light, air and soil, however
small amounts are detected in food and
drinking water
➢ The mechanism of action is the
insecticide binding at the GABAA site in
the gamma aminobutyric acid (GABA)
chloride ionophore complex, which inhibits
chloride flow into the nerve.

6. Organophosphorus
Pesticides
Organophosphates (also known as phosphate esters, or
OPEs) are a class of organophosphorus compounds
with the general structure O=P(OR)3, a central
phosphate molecule with alkyl or aromatic
substituents. They can be considered as esters of
phosphoric acid.
Where,
R1 and R2 may be alkoxy (methoxy, ethoxy, etc.)
X may be amino, p-nitrophenoxy group, etc.

7. Acetylcholine
What is the Action of Acetylcholine?
Acetylcholinesterase (AChE) is a cholinergic enzyme primarily found at
postsynaptic neuromuscular junctions, especially in muscles and nerves. It
immediately breaks down or hydrolyzes acetylcholine (ACh), a naturally
occurring neurotransmitter, into acetic acid and choline.

8. Acetylcholine is the chief neurotransmitter of the
parasympathetic nervous system, the part of the
automatic nervous system (a branch of the
peripheral nervous system) that contracts smooth
muscles, dilates blood vessels, increases bodily
secretions, and slows heart rate. Acetylcholine can
stimulate a response or block a response and thus
can have excitatory or inhibitory effects

9. Insect:
Insects are a class of invertebrates with a three-part body
(head, thorax and abdomen), three pairs of jointed legs, two
compound eyes and one pair of antennae. Insects usually
have wings.
Insecticides
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10. BHC
Benzene hexachloride is
a colorless solid with a
slight musty odor.
Some of Insecticides are…
DDT
It is exists as a colorless
and tasteless crystalline
solid
PARATHION
Organic phosphorus
compound well known
as an insecticide that is
extremely toxic to
humans.
PARAOXON
Saturn is a gas giant
and has several rings

11. Beta
Nearly about 5 to 14%
BHC (Benzene hexachloride)
Gamma
Nearly about 10 to 13%
Epsilon
About 3 to 4%
***The gamma BHC is
usually known as
Gammaxene or
Lindane
Alpha
About 55 to 70%
Delta
About 6 to 8%
The commercial BHC possesses 5
isomers. They are….

12. Chlorine combines with benzene, in the
presence of sunlight and in the absence of
oxygen as well as substitution catalysts, to
form hexachlorocyclohexane
Preparation of BHC

13. The insects that are not killed by DDT are killed by
Gammaxene (BHC). And also….
• Benzene hexachloride is used as an insecticide
on crops, in forestry, for seed treatment.
• It is used in the treatment of head and body
lice.
• It is used in pharmaceuticals.
• It is used to treat scabies.
• It is used in shampoo
Uses of BHC (C6H6Cl6)

14. TOXICITY
It has no contact action on human
system and so it is safe insecticide
for domestic use.

15. DDT is Dichloro-Diphenyl Trichloroethane. DDT is a
chemical compound with the formula C14H9Cl5. Under
standard conditions for temperature and pressure (STP),
this chemical compound exists as a colorless and tasteless
crystalline solid.
Dichloro Diphenyl trichloro ethane
DDT

16. Preparation of DDT
DDT is manufactured by exothermic condensation
of chlorobenzene with chloral at about 300C in
presence of oleum or 95-99% sulphuric acid.

17. TOXICITY:
DDT is transmitted to human body when people eat
the meat of birds and fishes that are injured by
eating DDT affected insecticides. Thus, the
DDT dissolved in fat harms human body.
However, the pests that were controlled / killed
using DDT, now a days they have developed
their resistance against DDT. It was proved in
1962. Since then, the use of DDT has been
limited

18. Uses of DDT:
Between the 1950s and the 1980s, DDT was widely
used in the agricultural industry as an
insecticide. The use of DDT to control diseases
like typhus and malaria was not uncommon in
the early 1940s.

19. Parathion
Among the most widely used pesticides is
parathion, an organophosphate. It is a
combustible liquid that is pale yellow to dark
brown in color and is not easily
combustible. Parathion is usually dissolved
in flammable hydrocarbon solvents such as
toluene or xylene in commercial products.

20. Preparation of Parathion:
Parathion is prepared by treating
diethylchlorothiophosphate with
sodium p-nitrophenate. Ther reaction
is carried out in chlorobenzene or in
aqueous medium in the presence of
emulsifier

21. Parathion is a restricted use organophosphate
insecticide/miticide used to control a broad
spectrum of pests on alfalfa, barley, canola,
corn, cotton, sorghum, soybeans, sunflowers,
and wheat. It is formulated as a liquid and
may be applied only using aerial equipment
Uses Of
Parathion:

22. Effects of Parathion:
Parathion, an organic phosphorus compound well known as an
insecticide that is extremely toxic to humans. The compound acts
in mammals, as in insects, as a cholinesterase inhibitor
(cholinesterase being the enzyme that controls the normal
functioning of the nervous system), causing death by inducing
respiratory failure. The specific antidote for poisoning by parathion
and other organophosphorus insecticides is atropine. Parathion
and similar insecticides must be handled with great care because
the substance is toxic if swallowed, inhaled, or absorbed through
the skin.

23. Paraoxon
Paraoxon is a parasympathomimetic which acts as a
cholinesterase inhibitor. It is an organophosphate
Oxon, and the active metabolite of the insecticide
parathion.
Paraoxon

24. Preparation Of Paraoxon:
Paraoxon is prepared by treating sodium-p-
nitrophenoxide with diethylchlorophosphate using
xylene as solvent.

25. Uses Of Paraoxon:
used as an ophthalmological drug against glaucoma. Paraoxon is one of
the most potent acetylcholinesterase-inhibiting insecticides available,
around 70% as potent as the nerve agent sarin, and so is now rarely used
as an insecticide due to the risk of poisoning to humans and other
animals.
It is easily absorbed through skin, and was allegedly used as an
assassination weapon by the apartheid-era South African chemical
weapons program Project Coast.

26. Toxicity & Effects:
Acute and chronic exposure to compounds like Pxn can lead to
neurotoxic effects associated with the human conditions called
cholinergic syndrome, intermediate syndrome, organophosphate-
induced delayed polyneuropathy, and chronic organophosphate-induced
neuropsychiatric disorder. The brain’s susceptibility to
anticholinesterase toxins and the distinct effects on synapses can leave
exposed individuals vulnerable to symptoms and neurological problems
for the rest of their lives

27. Herbicieds
03
The chemicals that are widely used in
the agricultural fields to control the
growth of herbs, weeds and bushes
which are called herbicides.

28. 2,4,5-trichlorophenoxy acetic acid is manufactured by
chlorinating 1,2,4-trichloro benzene in presence of
aluminum-mercury amalgam
2,4,5-trichlorophenoxy
acetic acid

29. ● 2,4,5-trichlorophenoxy acetic acid is manufactured by chlorinating 1,2,4-trichloro
benzene in presence of aluminum-mercury amalgam. 1,2,4,5-tetrachloro benzene thus
formed is treated with NaOH in methanol to form a mixture of 2,4,5-trichlorophenol
and 2,4,5-trichloromethoxy benzene. 2,4,5-trichloromethoxy benzene is separated
from the mixture by solvent extraction method. The left 2,4,5-trichlorophenol is
neutralized with caustic soda to produce 2,4,5-trichloro sodium phenate. Then the
product is reacted with sodium mono chloroacetic acid to form sodium salt of 2,4,5-
trichlorophenoxy acetic acid
Preparation Of 2,4,5-T:

31. Use of 2,4,5-T:
2,4,5-Trichlorophenoxyacetic acid (also known as 2,4,5-T), a synthetic
auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-
leafed plants. It was developed in the late 1940s and was widely used in
the agricultural industry until being phased out, starting in the late 1970s
due to toxicity concerns

32. Mode of Action:
2,4-T is a synthetic auxin, which is a class of plant growth regulators. It is
absorbed through the leaves and is translocated to the meristems of the
plant. Uncontrolled, unsustainable growth ensues causing stem curl-over,
leaf withering, and eventual plant death. 2,4-T is typically applied as an
amine salt, but more potent ester versions exist as well.

33. Effect of 2,4,5-T:
Human health effects from 2,4,5-T at low environmental doses or at bio-
monitored levels from low environmental exposures are unknown.
Intentional overdoses and unintentional high dose occupational exposures
to chlorophenoxy acid herbicides have resulted in weakness, headache,
dizziness, nausea, abdominal pain, myotonia, hypotension, renal and
hepatic injury, and delayed neuropathy. Co-metabolism of 2,4,5-T is
possible to produce 3,5-dichlorocatechol11 which, in turn, can be degraded
by Pseudomonas bacteria.

34. Thank You....