Agriculture Chemicals

1. Diels–Alder reaction
The Diels–Alder reaction is an organic chemical reaction between a conjugated
diene and a substituted alkene, commonly termed the dienophile, to form a
substituted cyclohexene system. It was first described by Otto Diels and Kurt Alder
in 1928, for which work they were awarded the Nobel Prize in Chemistry in 1950.[1][2]
The Diels–Alder reaction is particularly useful in synthetic organic chemistry as a
reliable method for forming 6-membered systems with good control over regio- and
stereochemical properties.
Mechanism of the Diels-Alder Reaction
Overlap between the highest occupied MO of the diene (HOMO) and the lowest
unoccupied MO of the dienophile (LUMO) is thermally allowed in the Diels Alder
Reaction, provided the orbitals are of similar energy. The reaction is facilitated by
electron-withdrawing groups on the dienophile, since this will lower the energy of
the LUMO. Good dienophiles often bear one or two of the following substituents:
CHO, COR, COOR, CN, C=C, Ph, or halogen. The diene component should be as
electron-rich as possible.
Endosulfan, also spelled Endosulphan, is a highly persistent and toxic crystalline
insecticide. Endosulfan is under the Cyclodiene subgroup of the of the
organochloringe group of pesticides.
Other Names: Benzoepin, Endocel, Parrysulfan, Phaser, Thiodan, Thionexv
IUPAC Name: 1,4,5,6,7,7-hexachloro-8,9,10-trinorborn-5-en-2,3-ylenebismethylene
sulfite OR 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-
benzodioxathiepine-3-oxide
Formula: C9H6Cl6O3S
Mechanism-The organochlorine pesticide endosulfan (ES) is used in several
countries as a wide spectrum insecticide on crops with high commercial value. Due
to its high toxicity to non-target animals, its persistence in the environment and its
ability to act as an endocrine disrupting compound in fish, ES use is currently
banned or restricted in many other countries.
Process for the preparation of malathion

2. Process for the preparation of malathion by reacting O,O-dimethyl-dithiophosphoric acid with
ethyl maleate in the presence of a solvent which forms a heterogeneous azeotrope with the O,O-
dimethyl-dithiophosphoric acid.
Use in crop protection-Malathion is a pesticide that is used to kill insects on
agricultural crops, on stored products, on golf courses, in home gardens, and in
outdoor sites where trees and shrubs are grown at home; it is also used to kill
mosquitoes and Mediterranean fruit flies (medflies) in large outdoor areas.
Physical / Chemical Properties of malahion
 Malathion is a colorless to amber liquid with a skunk- or garlic-like odor.
 Vapor pressure 1.78 x 10-4
mmHg at 25 °C or 5.3 mPa at 30 °C; also 1.2 x 10-4
to 8 x 10-6
mmHg at 20 °C
 Octanol-Water Partition Coefficient (log Kow) 2.75, 2.36-2.89
 Henry's constant may be estimated or derived experimentally. An
experimental value of 2.0 (± 1.2) x 10-7
(n = 6 experimental values,
dimensionless units) is reported based on a wetted-wall column,
concentration/concentration method.7
This value has been cited elsewhere as
4.9 x 10-9
atm·m3
/mol .Additional estimated values range from 2.4 x 10-7
to
1.0 x 10-6
at varying temperatures. An additional value of 5.68 x 10-8
mmHg
has been reported.
 Molecular weight 330.4 g/mol
 Solubility (water) 145 mg/L
 Soil Sorption Coefficient (Koc) 30, 93-1800 depending on soil type and
environmental conditions.
preparation-Liquid Dimethoate formulations comprising a solvent chosen among
liquids comprised of a compound having a ethylenglycol-propylenglycol co-
polymeric chain as well as mixtures thereof. These solvents diminish the use of VOC
solvents while still providing storage stable formulations.
used cropDimethoate is used against a broad range of insects such as thrips,
aphids, mites, and whiteflies(4), and on a number of crops including citrus, cotton,
fruit, olives, potatoes, tea, tobacco and vegetables
Physical and Chemical Properties
Pure dimethoate is a colourless crystalline solid with an odour of
mercaptan. Technical dimethoate (about 93% pure) varies from
off-white crystals to a grey semi-crystalline material. Some physical
and chemical properties of dimethoate are given in the International
Chemical Safety Card (pages 18-21).

3. Dimethoate is highly soluble in chloroform, methylene chloride,
benzene, toluene, alcohols, esters, and ketones, slightly soluble in
xylene, carbon tetrachloride, and aliphatic hydrocarbons, and partly
soluble in water.
Dimethoate is fairly stable in water and acid solution at room
temperature, and unstable in alkaline solution. On heating, it is
converted to O,S-dimethyl phosphorodithioate.
Pyrethroid insecticides are a special chemical class of active ingredients found in
many of the modern insecticides found on store shelves and used by pest
management professionals. The name pyrethroid means “pyrethrum-like” and
refers to the origin of this class of pesticides.
Characteristics of pyrethroids
Not all pesticides in the same class are equally toxic, or equally effective the same pests.
Nevertheless, most pyrethroid insecticides share the following characteristics:
 Low in toxicity to mammals and birds;
 High in toxicity to fish if applied directly to water;
 Require very low doses to kill insects (high arthropod toxicity);
 Fast-acting;
 Especially effective against chewing insects, though many pyrethroid
insecticides can be absorbed by the insect pest when it merely walks over the
dry residue;
 Bind tightly to soil and organic matter (therefore not as effective in
penetrating soil to kill underground pests);
 Dissolve very poorly in water.
Pyrethroids became popular as consumer insecticides in the 1990s as replacements for older
pesticides, like diazinon and Dursban® that were phased out for environmental and human
health reasons. Some pyrethroid insecticides last a long time in the environment (days or
weeks), especially when protected from sunlight. Others, such as allethrin and resmethrin, break
down within a few minutes to a few hours after application.
ex. of pyrethroid insecticides
Class Examples Area of Effect
Organochlorines DDT, toxaphene, dieldrin, aldrin
Reproductive, nervous, endocrine, and
immune system

4. Organophosphates Diazinon, glyphosate, malathion Central nervous system
Carbamates Carbofuran, aldicarb, carbaryl Central nervous system
Pyrethroids
Fenpropanthrin, deltamethrin,
cypermethrin
Poorly understood
Crop protection is the science and practice of managing, plant diseases, weeds and other pests
(both vertebrate and invertebrate)that damage agricultural crops and forestry. Agricultural crops
include field crops (maize, wheat, rice, etc.), vegetable crops (potatoes, cabbages, etc.) and fruits.
The crops in field are exposed to many factor. The crop plants may be damaged by insects, birds,
rodents, bacteria, etc. Crop protection encompasses:
 Pesticide-based approaches such as herbicides, insecticides and fungicides
 Biological pest control approaches such as cover crops, trap crops and beetle banks
 Barrier-based approaches such as agrotextiles and bird netting
 Animal psychology-based approaches such as bird scarers
 Biotechnology-based approaches such as plant breeding and genetic modification
Mancozeb-Manganese ethylene bisdithiocarbamte(FULL NAME)
 Molecular Formula-C8H12MnN4S8Zn
Usage
Mancozeb is a mixture of Maneb (M163500) and Zineb, a manganese and
zinc (1:1) complex mixture with the ethylene bis(dithiocarbamate) anionic
ligand. Mancozeb is a foliate fungicide used to protect cr ops in agriculture.
Mancozeb has a broader and more effective fungacidal activity than either of
its component on their own. Mancozeb also significantly enhances the copper
activity against several ba cteriosis.
prepn of mancozeb- firstly, for preparing mancozeb, mixing an organic
solvent with the wet product of mancozeb for dehydration by distillation;
secondly, with the solvent as a carrier, performing distilling dehydration by
virtue of jet heating or heating by use of a membrane type evaporator, and
realizing continuous operations of the dehydration step, and the steps of wet
pulverization, blending and packaging;
thirdly, performing simultaneous complexing, dehydration and crystal
transformation on maneb and zinc in the organic solvent; the third step is

5. capable of reducing the decomposition of the product, and therefore, the
pollution of harmful impurities and dust is reduced and fire accidents in the
product drying process is avoided. ex. Potato blight; Leaf spot; Scab;
Rust
Chemical and Physical Properties of mancozeb
1. Computed Properties
Molecular Weight
541.045725
g/mol
Hydrogen Bond Donor
Count
4
Hydrogen Bond Acceptor
Count
8
Rotatable Bond Count 6
Exact Mass
538.749952
g/mol
Monoisotopic Mass
538.749952
g/mol
Heavy Atom Count 22
Chlorothalonil
Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile)
Molecular Formula: C8Cl4N2
Uses
n the US, chlorothalonil is used predominantly on peanuts (about 34% of usage),
potatoes (about 12%), and tomatoes (about 7%), though the EPA recognizes its use

6. on many other crops. It is also used on golf courses and lawns (about 10%) and as a
preservative additive in some paints (about 13%), resins, emulsions, and coatings.
Physical Properties:
Physical Properties:
Chemical
name:
tetrachloroisophthalonitrile
Solubility
in water:
0.6 mg/l @ 25 degrees C (Considered insoluble).
Solubility
in solvents:
Soluble in acetone, butanone, dimethyl formamide, and dimethyl
sulfoxide (20 g/kg); cyclohexanone (30 g/kg); kerosene (< 10g/kg);
xylene (80 g/kg); methyl ethyl ketone; mineral seal oil (ALL @ 25
degrees C) (6).
Melting
point:
250-251 degrees C
Boiling
point:
350 degrees C
Vapor
pressure:
1.3 Pa @ 40 degrees C
Adsorption
Coefficient:
1,300 - 14,000 (calculated
Chemical organochlorine/fungicide
1st and 2nd Generation Pesticides
 1st Generation pesticides are simple, usually very toxic chemicals which harm
almost everything they come into contact with
 Considered to be any type of pesticide used large-scale before 1950's both
inorganic compounds and botanical pesticides
 Inorganic compounds include sulfur, arsenic, calcium arsenate, copper
acetoarsenite, hydrogen cyanide, mercury, lead,
 Highly toxic
 Persistent
 Accumulate

7.  Non-specific
 Botanical compounds include nicotine sulfate, rotenone, pyrethrum, and
chlordecone
o Usually non-persistent
o Highly toxic
Example- 1st Generation Pesticides:
 2500 BC- farmers began using the toxic chemical sulfur to kill off pests from
their crops
 15th century AD -a variety of chemicals such as, arsenic, hydrogen cyanide,
mercury and lead were put to use
 17th century -nicotine sulfate, derived from tobacco leaves was discovered as an
effective pesticide and ants were controlled with mixtures of honey and arsenic
 Other 1st generation pesticides such as chlordecone have only recently been
banned, and are only used infrequently in developing countries
 2nd Generation pesticides are synthetic compounds created for the intentional
use as a pesticide
o Persistent
o Toxic
o Short lived
o Result in biomagnification (chlorinated hydrocarbons like DDT)
o Water Soluble
However can also be helpful
 Organism specific (to a point)
 Less harmful to humans
2nd Generation-ex.
1874- DDT was first synthesized

8. 1939- Paul Hermann Müller discovered the insecticidal properties of DDT
1941- Aerosols developed in US
After WW2 BHC, aldrin, dieldrin, endrin, DDT and 2,4-D were introduced
and became immensly popular, cheap, and widespread
1958- Carbamates developed and put to use
1962- Silent Spring
1970's- organophosphates and carbamates dominate the pesticide market
1972- DDT usage is banned in the Federal Environmental Pesticide Control
Act
 1984- Methyl isocyanate industrial accident in Bhopal, India
no-observed-adverse-effect-level (NOAEL) is an important part of
the non-clinical risk assessment. It is a professional opinion based on
the design of the study, indication of the drug, expected
pharmacology, and spectrum of off-target effects. There is no
consistent standard definition of NOAEL.
Pesticide residues on crops are monitored through the use of
Maximum Residue Limits (MRL), which are based on the analysis of
the quantity of a given chemical remaining on food product samples.
Acceptable daily intake or ADI is a measure of the amount of a
specific substance (originally applied for a food additive, later also for a
residue of a veterinary drug or pesticide) in food or drinking water that
can be ingested (orally) on a daily basis over a lifetime without an
appreciable health risk. ADIs are expressed usually in milligrams (of the
substance) per kilograms of body weight per day.
The most important parameter is the matching of the Pre Harvest
Interval (PHI) (in days) of the chemical with the Natural Harvest
Interval (NHI) of the crop. Where, PHI is also known as the Waiting
Period, which is the period after the spray chemical residue remains on
the crop/fruit.
Pesticide residue refers to the pesticides that may remain on or in
food after they are applied to food crops. The levels of these residues
in foods are often stipulated by regulatory bodies in many countries.
Food and Pesticides safe use-Pesticides are widely used in
producing food to control pests such as insects, rodents,

9. weeds, bacteria, mold and fungus.Under the Food Quality
Protection Act (FQPA), EPA must ensure that all pesticides used
on food in the United States meet FQPA's stringent safety
standard. FQPA requires an explicit determination that a
pesticide’s use on food is safe for children and includes an
additional safety factor, up to tenfold if necessary, toaccount
for uncertainty in data relative to children.
Advantages of Chemical Pest Control
Effective when sudden outbreak occurs.
Sure method of control of pests.
Large areas could be covered in short period.
Selective application is possible.
Convenient to use.
Less manpower required.
Migration of insect is checked.
Limitation of Chemical Pest Control
Equipment needed for application.
Special expertise is necessary.
nontarget beneficial insects are affected.
Toxic residues in crops, soil, water and environment
Chemicals for Insect Control
-Pesticides include both the synthetic pesticides and plantderived pesticides.
-Synthetic pesticides includes a wide range of man made chemicals. These are
easy to use, fastacting and relatively inexpensive.
-Ideally, pesticides should be used as a last resort in IPM programs because of
their potential negative effect on theenvironment.
-Pesticides with the least negative impacts on nontarget organisms and the
environment are most usefu.
The Insecticide Act, 1968
-The Act is aimed to protect human life and environment.
-Prior to this Act, there were many accidental food poisoning cases in town of Kerala,
Tamil Nadu, West Bengal, Assam, Utter Pradesh and
Maharashtra.
-Thus to regulate manufacture, sale, distribution and use of pesticides, the insecticides
Act was enacted in 1968.
The Salient Features of InsecticideAct for goi-

10. -Establishment of a Central Insecticide Board and the Registration Committee for
granting certificates of registration to import or manufacture insecticides.
-License for manufacture, sell or exhibit for sale or distribute any insecticide.
-Establishment of a Central Insecticide laboratory.
-Regulation of transport and storage of insecticide.
-Provision for taking immediate action where risk to human being or vertebrate animals
is involved.
Pesticide Review by Govt of india Chlorothalonil, Iprodione, Propineb,
Thiodicarb, Thiophanate Methyle, Oxyfluorfen, Mancozeb, Malathion,
Diuron, 2, 4-D and Butachlor
SYNTHETIC PYRETHROIDS
SYMPTOMS OF POISONING
-Headache, fever
- wheezing, coughing
- sensation of swelling or tightness in the chest
- tremors
- irregular heartbeat
- extreme weakness
- nausea
antidote-Calcium gluconate and vitamins of the B complex can be used to protect the liver.
DITHIOCARBAMATES
SYMPTOMS OF POISONING
- itching
- cough
- scratchy throat
- inflammation of nose or throat
- sneezing
antidote- carbofuron, pirimicarb, propoxur, carbaryl
Symptoms of Anticoagulant Rodenticide Ingestion
 Bleeding is a common symptom of exposure to anticoagulant rodenticides. ...
 Bruising may occur as blood leaks into the skin.
 Blood loss often leads to weakness, lethargy, and decreased appetite.
 Bleeding into the lungs may lead to coughing (cats, dogs) or trouble breathing
 antidote- Coumarins, 1,3-Indandiones, Chlorophacinone, Pindone ,Diphacinone.

11. Using pesticides safely depends on many things. Some of the most
important factors include selecting the appropriate product, and using that
product according to the label directions. The label directions are written to
minimize the risk of problems and to define the legal uses for the product.
Pesticide application refers to the practical way in which pesticides,
(including herbicides, fungicides, insecticides, or nematode control agents)
are delivered to their biological targets (e.g. pest organism, crop or other
plant).
Health hazards due to pesticides
The many chemical substances that are collectively referred to as pesticides in
tervene in different vital metabolic processes in various organisms. The effects of
insecticides range from damage to the transmission of nerve impulses and inhibition
of blood clotting to paralysis of the respiratory and circulatory centers. Besides the
target organisms such as insects, fungi, or weeds, non-targeted organisms are also
always affected by pesticide use. These include wild animals and plants, domestic
animals and crops, and human beings. In humans, exposure to pesticides can lead
to unspecific adverse health effects that will be referred to here as poisonings