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6-23-1969

THE CHEMISTRY OF PESTICIDES

Walter R. Benson
Food and Drug Administration

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 Reproduced by the
U. S. DEPARTME",T OF HEAL TI!, EDUCATION, AND WELFARE
Fc·od and Drug Admilri.stration

THE CHEMISTRY OF PESTICIDES

Walter R. Benson
Pesticide Branch, Division of Food Chemistry, Bureau of Science
Food and Drug Administration, Washington, D. C.

Reprinted from
ANNALS OF THE NEW YORK ACADEMY OF SCIENCES
Volume 160, Article 1, Pages 7-29
June 23, 1969
This document is a U.S. government work and
is not subject to copyright in the United States.
 THE CHEMISTRY OF PESTICIDES

WaIter R. Benson
Pesticide.f Brallch, DivisiO/l of Food Chemistr}" Bureall of Science
"-ood and Drug Administration! Washingtoll, D. C.

INTRODUCTION
This review is limited to the structures ana a few reactions of the pesticides-
mainly in~ecticides-that affect mammalian systems and that are the subject of
papers by other authors in this monograph. There is no attempt to give a com-
plete review of the chemistry of pesticides. It is intended only to show the breadth
and depth of pesticide chemistry through the use of examples. With proper usc
of the references, and of the papers by Crosby, Freed and Montgomery, and
Owens in this monograph, the reader will be able to find information for other
chemicals.
NOMENCLATURE
Pesticides or economic poisons are defined in the Federal Insecticide, Fungi~
cide, and Rodenticide Act as " ... any substance or mixture of substances intended
for preventing, destroying, repelling or mitigating any insects, rodents. nema-
todes, fungi or weeds or any other forms of life declared to be pests; any substance
or mixture of substances intended for use as a plant regulator, defoliant or desic-
cant." Thus, the classification of a pesticide could be made by first naming the
living system that it controls and then listing functional groups wherever possible.
This is generally the form that we have used, as shown in TABLE ::.
However, this is not the only system used. For example, the U. S. Tariff Com-
mission first classifies synthetic organic chemicals according to whether they are
cyclic. Pesticides are classified further by the living system controlled, and finally
by categories containing similar organic functional groups.SJme authorities
classify pesticides alphabetically and then give the crops upon which they can
be used. Another arrangement is to list, first, the crop or livestock to be protected;
second, the pest that usually attacks it: and third, several pesticides for the con-
trol of each pest. In one classification, pesticides arc listed in the chronological
order in which their tolerances were cstablished. They have also been grouped
according to their pharmacologic action (e.g .. cholinesterase-inhibiting pesti-
cides) or by the way they can be analyzed (e.g., gas chromatography). These
classifications arc summarized in TABLF. 2. Recognition of the classification
sy~tems used by various groups is the first step toward understanding the complex
chemical reactions involved.
In any list of pesticides, a name must be used for each agent. However, many
mimes arc used today for the individual chemical or the mixture of chemicals.
The chemical name usually describes one compound and, if general enough, sev-
eral isomers, as well. However, this name is often cumbersome and awkward for
discussions and reports. Therefore, abbreviations and common names have been
adopted. Agreement to use one name is not always unanimous.
There is another nomenclature problem, since very few chemicals are prepared
and used in their pure state. When chemicals are diluted with materials to increase
their effectiveness, they are said to be formulatcd, and their names change once
more. The new name depends on such factors as the concentration, the diluent,
7
8 Annals New York Academy of Sciences
TABLE 1
CLASSIFICATION or PESTICIDE CHEMICALS"l1
_ _ _ • _ _ • _ _ _ _ _ _ .~_ -'0- _...,... _ _ _ _ _ _ _ _ _ _ •

. -----,--- -,-~ --- .-~.

I. Fungicides III. Insecticides (see TAllIE) for specifics)

A. Inorganic compounds containing A. Inorganic
1. Copper 1. Arsenicals·- Paris green
2. Others - NaAIF. (cryolite)
2. Mercury
B. Botanicals and derivatives
3. Chromium 1. Nicotine
4. Zinc 2. Pyrethrum
5. Other metallic compounds C. Biologicals
B. thllringlensis
6. Sulfur
D. Petroleum
B. Organic compounds
r:. Synthetic organic compounds
1. Dithiocarbamates I. Chlorinated
2. Phthalimides a. aldrin-toxaphene group
b. lindane and isomers (BHC)
3. Karathane c. DDT group
4. Dodine 2. Phosphorus (with and without sulfur)
5. Quinones a. aliphatic phosphates and
phosphonates
6. Pentachlorophenol b. vinyl phosphates
7. Others c. aromatic phosphates and
phosphonatcs
1I. Herbicides d. pyrophosphates
A. Inorganic compounds - NaCIO" 3. Carhamate
B. Organic compounds a. N-methy1carbamates - Sevin@, Buxop
b. N,N-dimcthylcarbamatc-Dimetilan®
I. Petroleum fractions
4. Others
2. Arsenicals
3. Phenoxy type IV. Miticides (see TABLE 3 for specifics)
a. 2,4-D A. Sulfites, sulfones. sulfides. sulfonates
b. 2,4,5-T B. Dinitropheno)s
c. other phenoxy and related C. Kelthane®
4. Phenylureas D. Others
5. Carbamate (thiol, N-phenyl)
V. Fumigants
6. Dinitrophenols A. Space and product - HCN, CHaBr
7. Triazines B. Soil type - CH"NCS, BrCH,CH.Br
R. Benzoic acids
VI. Defoliants and desiccants
9. High bromine content Phosphites, H.SO,
10. Phosphorus (aliphatic
V II. Rodent icides
phosphites, phosphates)
A. Anticoagulants
11. Amides Coumarins
12. Quaternary salts B. Other
13. Other organics I. Fluoroacetamide
2. I-Naphthyl thiourea
VIII. Other
A. Plant growth regulators - I-naphthylncetic
acid
B. Repcllents (insects, birds) - ally)
isothiocyanate
 Benson: Chemistry of Pesticides 9
TABLE 2
CLASSIFICATION OF PESTICIDES WITIJ EXAMPLES

Classification System Example

1. Plant or animal controlled Broad leaf plant. Norway rat

2. Functional chemical group C-CI, ArO-C-N-CH.
II I
OH
3. Alphabeticailisting by name Aldrin to zineb
4. Crop, livestock, or surface usually protected Potatoes, cattle, or freight cars
S. Pharmacological action Inhibition of cholinesterase
6. Others
a. Systemic or non systemic Insecticide
or Fumil!ant
b. Method of analysis Gas chromatography
7. Combinations of 1 through 6
Crop protected hystem 4) Potatoes
Animal controlled (system 1 ) Flea beetles (Epilrix species)
Systemic (system 6a) Insecticides found effective:
carbaryl, DDT. dieldrin. endosulfan,
and endrin

and combinations with other pesticides. These products have trade names. The
large number of names used for one chemical is a barrier to communication,
making international committees on nomenclature to establish standards for
adopting common names a necessity. It is essential that all interested groups parti-
cipate in the naming and in the use of the names agreed upon. In particular, the
cooperation of journal editors and authors is needed. . .
The rules for naming and indexing chemical compounds1. 2 help the reader to
find references to the pure chemical in Chemical Abstracts and elsewhere. The
rules are revised periodically to meet the demands of a changing scientific com-
munity. Nevertheless, TDE, ODD. Rhothane®, p,p'-DOD and l,l-dichloro-2,2-
bis(p-chlorophenyl)ethane, for example, all stand for essentially the same chemi-
cal. although one may be mOre specific than another. They are all used in the
pesticide literature.!! TOE is the approved name in the United States, although
DOD and p,p'-DDD are often used. Rhothanc"O is the registered name for a com-
mercial product. whereas the last name in the series above is the IUPAC· or
Chemical Ahslracl.\· name; it refers to the main isomer in the mixture.
The names listed in the U. S. Department of Agriculture "Summary of Regis-
tered Agricultural Pesticide Chemical Uses" and tf.ose used in the pesticide
regulations of the Food and Drug Administration are usually the best names
selected from a number of possibilities. Commercial names are not usually pub-
lished in government regulations. Other Iists:l may be consulted. If much greater
accuracy in naming is desired, it may be necessary to turn to laboratory research
because a great deal more work, for example, to establish spatial relationships
and purity, is needed before naming can be unambiguous.

INORGANIC CHEMISTRY

Inorganic compounds constitute about 10 per cent of the dollar value of the
total United States market. 4 One of the common inorganic chemicals is copper
• International Union of Pure and Applied Chemistry ..
10 Annals New York Academy of Sciences
sulfate; It IS used both as a pesticide and as a reagent for the andly,>is of other
pe\ticide\. In these u,es ,ome of the chemi'itry involved may be similar; for ex-
ample, copper (II) probably forms bonds with sulfhydryl group,> and perhaps
with other sulfur groups.
This is a quantitative reaction,5 as shown in REACTION 1.

(1)

A ma~" 435 mf1-

CClzH z
CuSo1·5H~O is thus incompatible with some of the dithiocarhamatcs. some
dithiophosphates, and some other sy\tems involving slilfllf groupings.
As seen in TABLE 1, other heavy metals are used as salts or in conjunction with
organic groups, as in phenylmercuric acetate. Daum ll has recently reviewed
the application of organometallics to agriculture.
Some non heavy metal pesticides (NaCIO a ) are used widely in the control of
plants. Sulfur in its many oxidation states will be covered under the head, "Or-
ganic Chemistry," although sulfur has long been used as free sulfur and with lime.

ORGANIC CHEMISTRY
The chemistry of organic pesticide compounds is scattered throughout the
literature,:l depending on the discipline studied or the emphasis given. These
organic pesticides are arranged in TABLE 1 by their action on living systems and
later by their chemical functional groups. Even with these groupings, it is not
easy to draw hard and fast rules about the chemical behavior of a particular
substance from its position in TABLE 1.
One of the important groups of chlorinated hydrocarbon inscctieides is the
aldrin-Toxaphene grQup (TABLE 3a). The chemistry of part of this group-the
diene group-was reviewed by Riclllschneider. 7 He lists the chemical evidence
for the ~tructure of aldrin, dieldrin, chlordane, heptachlor, Telodrin"", and scveral
other relatcd compounds; side products from the difh::rcnt manufacturing
processes are also discussed. The\e compounds resulting from sidc react ions may
be found as re,idues. This, of course, applies to all the approximately HOO chemi-
cals registered for usc in the United Slates and to other compounds not registcrcd.
but used abroad. Thus, it is important to know how a pesticidc is manufactured
and what its side products are. Somc of the reactions of aldrin aId dieldrin are
given in FIGURE I. Similar structures and reactions are given in FIGURE 2 for
isodrin and endrin.
Photodieldrin is several times more toxic than dieldrin (sec Crosby's puper in
this monograph.) In considering pesticide toxicity. much nwre work is needed in
the area of i..,o!ation and evaluation of photolytic products. since almost all
applied pesticides arc exposed to the Sllll \, rays before harvest. The conversions
in FIGURE I and FIGURE 2 illustrate the reactive portions of the molecules. The
chlorine atoms in aldrin. dieldrin, isodrin, and endrin arc relatively unreactive
toward base because ( 1) by elimination reactions, they would form double bonds
at bridge-head carbon atoms, in violation of Bredt's rule; (2) for low-energy
elimination reactions, the hydrogen and chlorine atoms are not in the proper
 Bcn~on: Chellli~,try'of Pcsticidc~ 11
il"ampiallar /1O\ill"I1S: and (j) iur displdcel:H:nt n':<lctiol1s it is ddJicuit for hase
10 allad the had,side of lhe i'd:li- ci"dolinc; ;,iOill;, attaehed to :,jipilatil' positions
hecalhc they are proin:ted ily itw bi..:yclic hridgc,ysiClll. '1 ile two chlorine atom,
:ltlached 10 olefins are known to Ie: liiln:,H:llw toward h:tse. This general
reaetlon wit Ii base has eXccptions, ilOWe'/Ci'. Adamllvic K review, and extends the
reaction of aromallc amines and light wilh chlorinated organic pesticides. Here
the bases do react to give colored materials, but the chemistry is as yet unknown.
Toxaphene and StrobaneQ" each contain many compounds, as shown by thin
layer chromatography (TLC) and gas-liquid chromatography (OLC). When
one examines the results of the chlorination of camphene, using 1: 1 molar ratios
of chlorine and camphene,H it is clear why so many compounds exist. The reaction
involves rearrangement, elimination, and addition. In the case of Toxaphene,
KOH reacts to dehydrochlorinate some or all of the compounds, in contrast to no
reaction with the aldrin group.
With the chlordane family, the principles of elimination and displacement
reactions still apply to the six CI atoms located in positions related to aldrin.
However, an allyilc chlorine atom i'i available in pure heptachlor that can give
the displacement reaction. and the eJiminatioi] reaction can occur with some
facility in chlordane and its i"liTJer~. i\ilyiic halogens arc geIler,llly displaced
with greater ease than chlorine in .,aturatcd compounds (FlGIJRE 3). The reactions
of aldrin and dieldrin apply equ;dly wl'll to the chlordane family of compounds.
with the exception of the extra chlorine atol1l~.
At this point It should be made dear that pesticides are llsu;llIy impure; for
example, technical chlordane contains 25--40 percent of compounds that arc not
the ~ub,tance shown in FIGURE 3 as chlordane. These other compounds arise [rom
the manufacturing process. Raw agricultural products may contain pesticides
from a previous spraying program. Thus, care must be exercised in attributing
chemical or biological reactions to allY one substance, unless the sample or
chemical has been thoroughly identified.
The DDT group (TABLE 3a) generally can lose HCI to form an olefin (DDE)
with base_ It can also lose a chlorine atom through chemical reduction to form
TDE (FIGURE 4). Castro reported 10 that, in a model system for biological de-
halogenation, iron (II) deuteroporphyrin was found to convert DDT to TOE. In
other studies,l1 chromium (fI) sulfate also reduced trihalomethyl groups in
varying degrees. depending on the concentration of chromium (II). The CCl 3
group is found in many pesticide~. in addition to DDT, such as captan and
trichloroacetic acid. Therefore, this reduction reaction might be expected in the~e
compounds, as well.
When dicofol (Kelthane ",) I, healed in a gas chromatographic column, it often
fragmenh into CHCl:: and a dlchlorohcnl.Ophenone. Sillce often only olle peak is
~een in addition to the solvent peak, this peak might he ca,iiy mi,taken for dicofol;
thu~, it might he a"umed to have chromatographed intact. This mistake is more
likely to he made,~ince dicofol can be chromatographed intact under proper
column condition.'" Caution i, therefore necessary in order "ot to attrihute a peak
in a gas chromatogram to a particular intact compound unless further data are
available (FIGURE 5).
Dilan{'" has an acidic hydrogen. This chemical property is used in the analysis 12
for at least two compounds found in Dilan('\l. The aei-form is dominant on the
basic side, and this form can react with ferric chloride to give a unique color for
Dilan'k!. The question should always be raised: How many compounds might one
encounter here that would react in a similar manner (FIGURE 5)? This must be
12 Annals New York Academy of Sciences
TABLL 3a
INSECTICIDES: HnOGENA1ED HYDROCARBONS (I'HIMARILY CHLOROHAU)(d·.NS)

Alphabetical Listing GroupcJ by Similarity of ~truclure

aldrin I) Aldrin-Toxaphene group

ben7ene hexachloride (BHC) aldrin
chlordane chlordane
Chlorobenzilate dieldrin
chloroform endosulfan (Thiodan)
chloropicrin endIin
dichloropropene heptachlor
DDD (see TDE) -di,;lil'HQPwp8R8
DDT Kepone
dicofol mirex
dieldrin Strobane®
Dilan~Y Toxaphene
cndo,ulian (Thiodan)
endrin 2) BHC group
ethylene dibromidc benzene hexachloride
ethylene dichloride (also a fungicide)
heptachlor lindane
Kclthanc('!l (sec (\icoiol)
Kcpone :1) DDT group
lindane (part of BHC) Chlnrohen7.ilate
methoxychlor DDT
methyl hromide dieofol (Kellhanc"")
mirex Dilan'«'
methyl chloride mcthoxyehlor
orthodichlorobcnzcnc nrthodich lorohenlcnc
paradichlorobenzene ra radichlorohenzcne
Pcrthanc~J!.! Penhane
Propylene dichloride TOE (DOD) (saturated)
Rhothanc'1li hec TDE)
Strobane'" 4) Aliphatic halides (low carbon chain)
TOE (DOD) (Rhothane O,) chloroform
Telone chloropicrin
Tetrachloroethylene Dichloropropene
Thiodan@ (,ee endosulfan) ethylene dibromide
Toxaphene ethylene dichloride
Trichloroethylene (trichloroethene) methyl bromide
methyl chloride
Propylene dichloride
Tclone
Tet rachloroethylenc
Trichloroethylene

kept in mind for all of the pesticides and the naturally occurring compounds
that remain after a pre<tnalytical clean lip procedure and that may be present in
relatively high concentrations along with the pesticide.
Methoxychlor and PcrthaneC,v can lose Hel with base, as docs DDT. How-
ever this ahility to lose Hel is apparently not important in the toxicity to insects.
It appears that the shape or size of the DDT group of compounds is an important
factor, since model compounds containing no chlorine have biological activity. \:I
Cristol el al. 14 and Hine et a/.'" have studied the loss of Hel from benzene
hexachloride (HHC) isomers in base. It appears that the f:Hsomer is about 10,000
times more stahle in nature and toward base than the other isomers tested. With
an electron capture detector in G Le, the f3-isomer is also about half as sensitive
in response as an equivalent amollnt of the other SHe isomers. Although no
 Benson: Chemistry of Pc~ticides 13
TAIH E:ln

Abatc(ilj 1) Aliphatic phosphates (trialkyl)

azinph",methyl (Guthion'I<-) dcmcton
Baytex V" -- (sec Fenthion) dimcthoatc
Bidrin 00 dioxathion
Birlane',1) Di-Syston
carbophenothion (Trithion r",) ethion
Ciodrin® malathion
Co-Ral (see coumaphos) phorate (Thimet)
coumaphos (Co-Ral) TEPP (Pyro Phosphate)
ODVP (sec dichlorvos)
demcton 2) Vinyl phosphate or similar
diazinon Bidrin®
Dibrom (sec nalecl) Birlanc@
clichlorvos (DDVP, Vapona) Ciodrin@
dimcthoate dichlol'vos (DDVP)
dio;(alhion (DelnavO,,) mcvinphos
Diptcrex (<,ce trichlorofon) nalcd (Dibl'om)
disulfoton (Di-Syston~") phosphamidon
Di-Syston (see dislilfoton) trichlorfon (phosphonatc)
Dylox (see trichlorfon)
EPN 3) Aromatic phosphates
ethion Abate
fenthion (Baytex 00 ) azinphosmelhyl (Glithion)
Glithion® (sec azinphosmethyl) carbophcnllthion (Trithion)
malathion diazinon
methyl parathion EPN (phosphonate)
Methyl Trithion"" fcnthion (Baytex)
mcvinphos (Phosdrin@) methyl parathion
naled (Dibrom"") Methyl Trithion
Ncmacidc® (V-C Ll) Nemacide® (V-C 13)
parathion parathion
phorate (Thimct <0) ronnel
Phosclrin® (see mcvinphos) Ruelene®
phosphamidon
ronnel
Ruelene®
TEPP
trichlorfon IDylox, Oipterex)
Trithion'ilI (sec Carbophcnothion)

connection has been shown bctw.:.:n th.:s.: two fach. th.: d.:hydrochlorination
work ha~ produced a fundamental tnlth: initial tranI' confonnat:'ln of th.: Hand
CI in the dehydrohalogenation f.:action apparently doe~ not OC,llr readily in the
,B-isomer, and trans elimination i, favor.:d for this and other systems. Other
configuration'., "uch as cis that might lead to elimination require great.::!" energies
of activation, This Irans dehydrochlorination is th.::rdor.:: fundamental to all
chlorinated hydrocarbon systems (REACTION 2).

H 0 A 0
:--E base~
~(,:-c-
/1. ~ (2)
Ii. • CI B E
B
The main product of dehydrohalogenation of BHe is 1,2,4-trichlorobenzene.
14 Annals New York Academy of Sciences
TABU'. ,c
Alphahclir.:;dly LI'tlcd Similar rUlH:lionai (Jr(H.~ps

Banol 1) -N-mcthylcarbamates
carbaryl (Sevin"') Banol
Bayer 37344 Bayer 37344
Bayer 39007 Bayer 39007
Bayer 44646 Bayer 44646
Dessin® carbaryl
Isolan® NIA 10242
Dimetan Tranid
Dimctilan(<9 Temik
MCA -- 600 MC-A-600
NIA 10242 RE-5353
Pyranlat0v U. C. 10854 (H-H757)
Pyrolan@ Zectran
RE-5353 (Bux(W)
SevinQO (sec carbaryl) 2) N,N-dimethylcMbamate
Temik@ Dimetan
Tranid® Dimctilan
U. C. 10854 (H-8757) Isolan
Zectran@ Pyramat
Pyrolan

1) Carbonate
Dcssin

CIli$DHCI
CI

==
~CICI
CI
[0)
~
CO CO :: 00"0'"
D

q~H
CI CI .
CI CI
o H H

j H2S~40
CI H
ALDRIN ALDRIN

HzO

~ ~
CI~:

co4~"
CI~II h.v

CI CI

H CI 0H CI CI 0

H OH
CROSBY, 1966 PHOTODIELDRIN KORTE,I965
IN SOLUTION ROSEN,I966 IN SOLUTION
IN SOLID STATE AND IN RABBITS

FIGURE I. Aldrin-dieldrin reactions.

 Benson: Chemistry of Pesticides 15
TABLE 3d
INSECTICIDES: OTHER CHEMICALS

Alphabetically U,\cd By Similar Structure of Compounds

-------
acrylonitrile 1) Sulfides, Sulfones, Sulfites, and Sulfonates
allethrin (aluminum phosphide) Aramite®
Aramite® chlorbenside
Binapacryl fenson
calcium arsenate Genite 923
calcium cyanide ovex
carbon disulfide Sulphenone
Chlorbenside tetradifon (Tedion)
Cryolite Thanite
dinitrobutylphcnol
dinitrocrcsol 2) Dinitrophenols
dinitrocyclohexylphenol binapacryl
diphenylamine (\initrobutylphenol
ethyl formate (\initrocresol
ethylene oxide dinitrocyclohcxylphenol
fenson
hydrogen cyanide 1) Inorganic
Genite 923® aluminum phosphide
lead arsenate calcium arsenate
Lethane 384(iy calcium cyanide
lime sulfur cryolite
MetaldchYdc hydrogen cyanide
methyl formate lead arsenate
Morestan® lime sulfur
naphthalene Paris green (copper acetoarsenite)
nicotine sulfate Sulfur
ovex
paris green (copper 4) Other 'Synthetic Organic
acetoarsenite) acrylonitrile Lethane 384
piperonyl butoxide allethrin metaldehyde
propylene oxide carbon disulfide methyl formate
pyrethrins (active cpd) diphenylamine Morestan
pyrethrum (whole-dried ethyl formate naphthalene
flower) ethylene oxide piperonyl butoxide
rotenone hydrogen cyanide propylene oxide
ryania
Sabadilla 5) Natural Occurring
Sulfur nicotine sulfate
Sulphen()ncQ~ pyrelhrins (active compounds)
Tcdion"v (see tctradifon) pyrethrum <whole-dried flower)
tctradifon (Tedion('"") rotenone
Thanite® ryania
sabadilla

Once the first HCl molecule is eliminated, the other two Hel molecules are lost
so rapidly that the bracketed species havc not been isolated (FIGURE 6).
Reports on phosphorus chemistry have greatly increased in recent years, due
in part to the rapid growth in phosphate pesticides research. Some of the general
reactions they can undergo are pyrolysis, hydrolysis and oxidation (FIGURE 7).
NUcleophiles, such as NH~OH, oximate anions, hydrogen peroxide ions, and
O-Cl, which show the common structural features of an electronegative atom
with unshared electrons (X to the attacking atom, all exhibit reactivity toward
phosphoryl phosphorus. much greater than would be predicted from their
basicities 1fi (REACTION 3).
16 Annals New York Academy of Sciences

x=leaving group

[0]
CI
-=_t CI

h.v.
or
heat

CI

FIGURE 2. Isodrin-endrin reactions.

CI~
CI~ S02CI2
PEROXIDl
o
Xb Atb
CI

CI
CI

H
~I H

-
[0]

0
CI

CI
CI

H
~II· H
H
0

H CI H CI H
CHLORDENE
6 CI HEPTACHLOR HEPTACHLOR EPOXIDE
-7 CI 7 CI

1
CI2 1 CI 2

CI
~ ' CI~:H
CI H
CI

HH CI
CI

I H
CI H~

H CI
'¥;)I
CI

I H
H

CI
H CI Cf H-O H
CHLORDANE ENNEACHLOR
8 CI 9 CI 6 CI

l'I<aIRL 1. Chlnnlane family H·aelions.

 Bcnson: Chcm istry of Pesticides 17

FIGURE 4. DDT family reactions.

~C13
~
Ca,'-O-"----=.;..:t:::.-.. . CI~
~~
~CI
+ HCCI3

OICOFOL P. p'- OICHLOROBENZOPHENONE

(KELTHANE ®)

~",-oqt"" ~"'-''''-Q-tJ-,.
METHOXYCHLOR PERTHANE ®

~,-< ~t+"O, BASE,

OILAN ® ACI-rORM GIVES A COLOR

WITH r.CIJ
FIGURE S. DDT analogues.

It is well documented that phosphate insecticides can phosphorylate enzymes

and other parts of living systems because they have good leaving groups. However.
the herhicidal aliphatic phosphates have poor leaving groups and. relatively
speaking, do not inhibit cholinesterase. With heating under macro conditions,
aliphatic phosphates can alkylate ar.1ines. 16 Aliphatic amines should be even
easier to alkyl ate than aromatic amines, or anilines (FIGURE 8).
18 Annals New York Academy of Sciences
Pho\phonatl:\ arc lrul: I:xamplcs of organophosphorlls COl1lp(Jllnds. th;!t is.
compounds containing a direc: carhon-phosphorus bond. FPN and trichlorfon
servl: as examples of pilosphollate pesticide~ presently in Il.se (H(;I;RF 'J).
Trichlorfon not only rearranges. hut also ioses, Hel to give DDVP. The driving
force for the rl:aclion may he the fonnaticn of a new phosphorus-oxygen hondo
The relation hetwel:n the two hydrolysis products is given for trichlorfon and
DDVP. The rearrangement of trichlorfon in 'water can he followed by gas chrom-
atography.17 The products are extracted periodically into a solvent that can be
injected directly into a gas chromatograph and followed as long as phosphorus
is present in the molecule.

CI
" e, ~ IICllJc,i
Q erxYl ~ ,"ce'
10
" l
cli
CI L~CI J L
Cl CI CI J
1
BHC I-HCI
BASE
h.v. 't'

3CI2 + 01 ~
I
1.2.4- TRICHLORO-
BENZENE
(11
~
CI

CI
CI

MAIN PRODUCT
h(;URL 6. BRC dchydrohalogenation.

/,'S

6°")'~
NO z
PARATHION

j~'p
o~::: +
o
t
H-S-P(O-Etlz

NOz

S-ETHYL ISOMER
FI(dJRL 7. Parathion It'at.:tions.
 Benson: Chemistry of Pesticides 19
/,0 /0
(RO)2 P'o/Ar + R~0-H~(RO)2 P"'--o/R'

P,o CLEAVAGE
+ArOH

PHOSHORYLATION

C .... O CLEAVAGE

ALKYLATION
F1GURE 8. Phosphate reactions,

FIGURE 9. Phosphonate reactions.

Heterocyclic aromatic groups and aromatic carbocyclic groups behave similarly

in phosphate peslicides. Guthion® is hydrolyzed to three products, all of which
have been used to determine the amount of Guthion® present (FIGURE 10). Ana-
lytical methods based upon these hydrolysis products illustrate the interferences in
a "valid" analysis. In an impure sample. low or high yields can be obtained for
either the parent or the metabolites, depending upon which method is used-that
is, which compounu is being detcrmined-unless the analyticCiI method is specific
for the intact compound.
Dimcthoatc can be hydrolyzed at the amide Imkage as well as the P-O
(phosphate) bond. This is true for other phosphate pesticides. as well. Malathion
also can hydrolyze at the C-S linkage. leaving the two sulfur atoms with the
phosphorus atom, as shown (FIGURE 11). Elimination appears to be the cause of
20 Annals New York Academy of Sciences

DIAZINON AZiNOPHOSMETHYL
(GUTHION®) g
E )1.
{CHJ O)2 P\JJ:U c.,++ (CH'OI'<-~ ~ '-o/H +CH,O
5! 5 V N H2
~2
_ dio.ot ....
(I)
Amax -420 m~ DYE 12) coupl.
FIGURE 10. Heterocyclic pho..,phute rcactHlns.

MALATHION

FIGURE 11. Hydrolysis of phosphates,

.... s
(CH3 CHZ-OI2 P "'-. ~ /'... ./
S S..... "-.../

PHORATE (THIMET ®) i •• i ..il .. ,

FIGURE 12, Oxidation of disulfoton,

 Benson: Chemistry of Pesticides 21
the formation of thi~ dimethyl dithiophosphoric acid and fumaric acid. Other
products can form. with the u\ual displacement reaction.
An isolated sulfide group can form sulfoxides and sulfones. These oxidation
products, at least in the phosphate ~eries, arc usually hetter cholinesterase inhibi-
tors than the parent compound (fIGURE 12). '
In general, phosphate pesticides inhibit acetylcholinestera~,e irreversibly.
whereas N-methyl- and N,N-dimethylearbamate pesticides inhibit reversibly. This
first reaction is said to be a transphosphorylation process and the second a
transcarbamylation 1M process (sec Wil,on's paper and O'Brien's paper in this
monograph). More work is needed on these reactions in plants and animals, since
the,e two processes may form compounds that would lead to aliphatic phosphate
and carbamate residues th,it may be neither extractable nor rapidly degraded. This
type of reaction with natural products could apply to many pesticides other than
carbamates and phosphates.
The carhamate group is found in a large variety of pesticides-in\ecticides,
herhicide,>. and flillgicide,--and in drugs. Typical of the insect icidal carhamates
(FIGlJRE 13) (ary 1 N-mcthylcarbamates) used in this country is carbaryl
(Sevin"). The,e carhamate imecticide" can he hydrolyzed with various bases!"
within minute,. whereas the herbicidal N-phl~llylcarhal11ates require much longer
period~ of hydroly~i~ under the same conditions. The N-mcthylcarhamates can
be nitro~ated quantitatively. or nearly quantitatively, on the ring. with the nitrogen
replacing the hydrogen.l!I When carharyl and other N-melhylcarhamate in-
secticides arc heated 20 or bombarded with an electron heam 21 or whcn carbaryl
is photolyzed. 22 ,2:S I-naphthol or the corresponding phenol <1nd methyl isocyanate
are formed. Some new cholinesterase-inhibiting compounds were also reported.
Since methyl isocyanate appears to form easily, its chemistry was studied. Methyl
isocyanate was found to he selective in reacting with various hydroxyJ24.2G and
other groups after reaction. The N,N-dimethylearbamates from NMR studies
have a planar carbam<1te group.26 These carbamate insecticides have a very
narrow band in the infrared, attributed to the Cc.{) absorption. 27
Eptam (ethyl di-n-propylthiolcarhamate), a herbicide. is hydrolyzed by watcr
in a first-order reaction at 20" C, yielding ethyl mercaptan, carbon dioxide and
dipropylamine (REACTION 4) .
II
o . H 0
CH3 CH2 -S-C-N (CH2 CH 2 CH3 )2..:..:z.::; CH3 CH2 SH+ CO2 +H-N(CH2 CH2 CH3 )2
(4)
Eptam
Ferbam i~ a dithioearbamatc and a fungicide (RFIIC'lION 5).

Fe
ls~ S
)C~N(CH3J --=-=-+
[0]
CH33
~
(CH3 )2 N c;-S-S
~
C;-N(CH3 )Z
(5)
TilJram
+ other pro due t 5
It reacts with air and light to give decompo~ition products of unknown
\tructure~; however, thiram is probably one of them." V<1parn'''', a soil fumigant,
decompose~ to a to.{ic, gaseou~ sub\tancc. methyl isothiocyanate (REliCTiON 6).
Clearly, the carbamates arc a versatile group of pesticides.
H 5
I /I 51
CH3 -N-C-5- No+ ~CH3-N=C=S (6)
Methyl Isocyanate
22 Annals New York Academy of Sciences
2-Cyclohexyl-4,6-dinitrophenol (DNOCHP) is acidic and can also form mol-
ecular compounds (i.e., addition complexes) with aromatic and aliphatic hydro-
carbons, amines, phenols, and other compounds similar to picric acid.
Karathane®, an ester of a similar dinitrophenol, would be expected to behave in
a manner similar to DNOCHP, since it is a mixed acid anhydride and thus is
easily hydrolyzed to another dinitro alkylated phenol (FIGURE 14).
Sulfonates are generally difficult to hydrolyze; ovex is no exception. As with
most sulfonates the 0-0 bond (not the S-O bond) is cleaved during hydrolysis.
When an aliphatic alcohol is a part of the sulfonate, c-o bond cleavage would
be expected to give alkylation.

O-H

~
VJ
+R-X H
1 I
O-C-N-'- CH3

o . . . .NO
~N-CH'
VJ
FIGURE 13. Aryl N-mdhycarbamatc (carbaryl) rt·actiuns.

0-~-CH-CHCH3
rHl
o,NO~-C,H.

N~ N~ ®
DINITROCYCLOHEXYLPHENOL KARATHANE
(ACIDIC) (DNOCHPI_______ (Tre or anhydride)
- - - - - MOLECULAR

Clo-~
- ~-0-O~
~ -
CI COMPOUNDS c
AMINES, HC,
PHENOLS•• tc:.

OVEX

~=a=:~o~o~
PIPEROi-JYL BUTOXIDE
hGURE 14. Other in,ccliciocs.
 Bcnson: (,hcm istry of Pesticides 23
HI H
I ./

('(' + A-iI'l-'
AMlNOTRIAZOLE 'GLUCOSIDE

FiGURE 15. Heterocyclic herbidde,.

There arc many more miticidcs and insecticides (Sec list in TABLE 3). For
further information, consult the work of scientists in thi~ monograph. and that of
\cienti\ts associated with the manufacturer of the particular product.
Piperonyl butoxide (FIGURE 14) is not in itself an insecticide. but it acts as a
powerful ~ynergist for many of the phosphate, carbamate. pyrethrin. and other
types of insecticides. The methylenedioxy group is fairly stable~ but this ring
system can be opened with acid to form formaldehyde and the dihydroxy alkyl
benzene.
Like other amines. aminotriazole, or amitrol forms derivatives with carbonyl
compounds, which may account for the ease of formation of glucosides
and other metabolites (FIGURE 15). Free aniines, like amitrol and anilines, are in
general easily oxidized. Coupling would bE' expected from such an oxidation.
among other rewlts (Sec the paper by Freed ~ Montgomery on herbicidal chem-
istry in this monograph).
One of the reactive sites of simazine is at the chlorine-carbon bond. This
position appears to be generally reactive for all the triazine chemicals (FIG-
llln: 15). Free radical intermolecular alkylation may hc another type of reaction
involving the melhylthio- and methoxy triazine chemical,.
Captan is one of several phthalimide-type fungicides u\ed in the United States.

.
The reactive portion appcar~ to be in the S-C-Cl: l group (sec IO'.ACTlON 7) but.

oJ q

~
/CI
N-~-C,CC,'---- l5'-C-C~ ~
rr a
ThlOphosgene
;l Cysteine ~C02H
I
S'-.,./'NH
~
I (7)

a~ with aldrin. the double bond also forms cpoxides (Sec the paper by Owens on
fungicidal chcmi~try in this monograph).
There is a large group of fumigant chemicals that generally alkylate various
24 Annals New York Academy of Sciences
amine~. mereaptans. and alcohols. both in and outside of the living "y,tem (REAC-
TION H). CH3
R-:-S-H R-S-CH3 CH3Br jJ R-~-CH3
+
CH3 -Br + HBr ... R N-CH (8)
z/ 3
H
R-O-H
Methyl bromide is a primary example. Using radiolabelcd CIHa-Br under
conditions simulating the fumigation of wheat. Winteringham et a/. 2M and
Bridges 2H reported that the histidine and lysine components in wheat were
methylated on the basie amino groupings. Alkylation took place. as well. on
the S-H and O-H groups in other naturally occurring compounds.
When used as a fumigant of spices, ethylene oxide has been reported!lO to give
ethylene chlorohydrin, ethylene glycol. and hydroxyethyl ethers of carbohydrates
(REACTION 9).
R 0 H-O R!...O
t
'c/ "-cH I
z+ CI- or R'OH ----? R-C-CHZ and R-C-CHZ I
H
./'
~ tl O-H (9)
H O-H H-OI
I ./
R-C-CHZ R-C-CHZ
I
CI O-R'
Propylene oxide·1o behaves similarly. If these relatively unstrained epoxides
are opened by chloride ion, carbohydrates, and wattr, should other epoxides be
expected to behave similarly?
Acrylonitrile, another fumigant, is known to add rapidly to mercaptans and
certain amines a1 , as seen in REACTION 10.
R-~' + CHz=CH-C=N ~R-X-CHz-'fH' C=.N (10)
H H
Crosby discusses some other aspects of the organic chemistry of pesticides
in this monograph.
ANALYTICAL CHEMISTRY
Burchfield discusses instrumentation in pesticide analyses in this mono-
graph. However, the chemical bases for some analytical procedures have been
given as chemical reactions in previous sections of this paper. A recent survey
(November. I 964-0ctober, 1966) of the latest developments in pesticide resi-
due analysis was reported by Williams and Cook.:12 Where possible, this report
devoted attention to the chemistry involved in the analysis. These three sources.
together with their ~eferences, will cover analytical chemistry adequately.
PHYSICAL CHEMISTRY
The physicochemical properties of pesticides are often utilized to obtain
an ... wers to questions about such factors as purity. volatility. therm;\1 stability.
polarity, and partition values. For example. phase changes arc used to determine
purity (cryoscopic measurements, m.p., etc.). Beroza and associates. among
many investigators, have been particularly active with physicochemical pl,lra-
meters involving partition values for many pesticides. reaction-gas chromatog-
raphy, etc. They also reported that DDT (m.p. 108.5, with a vapor pressure of
1.9 X 10. 7 mm Hg at 20°C) is rapidly co-distilled with water at room and higher
 Benson: Chemistry of Pesticides 25
tl'lllpcr'ltlircs."" This may he what is expected for highly divided DOT. From the
data it appears th,li DDT i, not ';oluhle in waler, even at p,lrl'> per hill ion (pph)
lewis, ,11)(1 i, 1,,,1 at a constant rate from Ihe pi;Jcid water's 'lIrLI('e. Samples con-
lainlng [)/)"/, or DDT wmhined with other pesti\:ides. and wate' mllst therefore
he protected from this kind of lo,s if the analysis is to reflect the DDT content
at the t i Ille the sample is \:ollected.
Another lise of physicochemical properties of pesti\:ides is (0 he found in their
chromatographic hehavior. The Food and Drug Administratiol1 develops and
uses methods of analysis that can separate and quantitatively determine a large
numher of pesticides on an individual basis in one analysisa4~7 These are
multiple detection system~; they must determine many pesticides with the same
analysis. Several reports have appeared on TLC and GLC, hut a great deal more
work is needed on the general physicochemical properties of pesticides and their
metabolites. Nuclear magnetic resonance. 2 (; infrared spectromet ry 27 and mass
spectrometry have already been mentioned as techniques that show how car-
hamates behave. Insight into the penetration, adsorption, translocation, and
activation of pesticides has been obtained and can be further explored through
the physicochemical approach.
BIOCHEMISTRY
A fairly complete review through Decemher 31, 1965 was compiled hy
Menzie"" on the metabolism of pesticides. Current reviews arc availahle in reports
by working committees of the Food and Agriculture Organization (FAO) and
IUPAC. Much of the work on metaholism has heen done or is being done hy the
companies that market or that arc hoping to market a particular pesticide. These
data gradually arc reported in the literature. Some government and university
\cientists are studying metabolism; e.g. Baron and Doherty:19 at the Food and Drug
Administration studied the metabolism of Banol® (3.4-dimethyl-6-chlorophenyl
N-methylcarhamate). an experimental carbamate insecticide. and Korte and
Arent40 at the University of Bonn reported the metabolism of dieldrin in rabbits.
Korte also synthesized the metabolic product (See diol in FIGURE 2). Refer to
Fukuto and Metcalf's paper in this monograph for a summary of this rapidly
expanding field.
PESTlCmE CHEMISTRY WITHIN OTHER DISCIPI.INES
The for<~g()ing are the acknowledged suhdivisions of chemistry. How are
pe,ticide\ heing studied in other disciplines where chemistry plays a minor role?
Ben\on and lone,:1 have cited ~ome of the outstanding references :Ind sources
of information in the literature of pesticide chemistry. Any research program
depends upon the informar;on sciences. Shepard has prepared an economic re-
view11 of the pe\ticide.s (pounds produced, total sales. pounds sold, cost per
unit, etc.) for many years. Some of his data come from the Tariff Commission
Report on Pesticides. Plimmer, Rosen, Roburn, Crosby. Gunther. Slade. Casida,
and others with their associates arc gradually reporting on the photochemistry of
pesticides. Soil hiochemi\try is a complex area discussed in compendia and
several forthcomin,b hooks:l~ Jacobson 1:1 has reviewed the isolation. identification.
and ~ynthe~is of insect sex attractants. Insect chemosterilants have been reviewed
hy Borkovec. 14 There is no single book on the chemical manufacture of pesti-
cides; however, the palent literature for each individual pesticide would be the
place to begin. The American Chemical Society has sponsored a symposium
on the chemistry of organophosphate pesticides. 45
26 Annals New York Academy of Science~

CONCLUSIONS

Chemical studics on the behavior of pe,ticides have contributed greatly to our

understanding of the biological behavior of pesticides. Some outstanding studies
of the chemical reactions of pesticides have heen presented. The chemical re-
actions, physical behavior, and ideas for one pesticide apply to many other com-
pounds. Some precautions and several inherent problems have been raised. No
one as yet, however, has a foolproof method for predicting the biological activity
of a pesticide under t~e conditions found in the cornfield, for dample. This may
come eventually when we learn much more about the behavior of the chemicals
and the biological system, to he controlled. In achieving this method of prediction,
man will learn more a10ut his own life and ways of protecting it 'rom the inherent
risk of using the\e reactive chemicals. '

[NOTE ADDED IN PROOF: Between the time that this manuscript was pre-
pared and the actual time of pllhlication. a numher of outstanding technical books
and articles have appeared which would bring the reader closer to covering the
litcrature of pesticide chemi\try and its principles.
The National Academy of Sciences 11i is publishing a series of six volumes on
the Principles 0/ Plant I1nd Animal Pe.l"( Control. most of which have already
appeared in print. This set should prove invaluahle as a supplement to this mono-
graph. In the area of pesticide analysis. the Pesticide A Ill/lyrical MUllllal of the
Food and Drug Administration has been expanded to cover all pesticides that have
been approved for use on raw agricultural products:17 This manual was revised
and corrected in 1968. and periodic updatings are distributed. In the area of
metabolism, two books have appeared since Menzie's review::lH the book by
O'Brien"] covers the insecticides well; Hodgson's book,48 although using the word
"pesticide." actually deals mainly with the enzymatic oxidation of insecticides
together with metabolites, their synergists, model compounds, and some drugs.
Herbicidal degradations are covered by the treatise by Kearney and Kaufman 42
and the fungicides hy an advanced treatise in two volumes edited by Torgeson. 52
A numher of important specific reference, have also appeared. hut only those
which reflect in a major way on work presented here have heen included. Although
HHC docs in general hreak down with ha<,c a\ shown in j'J(;{JlH' (,. the bracketed
pentachlof(Jcyclohexene compound has recently heen fOllnd in soil and has been
o,ynthe\ized independently.1H
A recent review of the alkylating properties of alkyl thiophosphatesr,o showed
that this properly could be a major mode of reaction of this type of pesticide with
amines and mercaptans, (See FIGURE X where X is nitrogen, sulfur. or oxygen.)
A major examination of the N M R properties of pesticides is in progress for the
organophosphorus pesticides.,,:1 chlorinated hydrocarhon pesticides 54 and carba-
mate pesticides,';'; and is expected to he continued for other classes of pesticides.
Summary reports of the Commission of the Pesticides Section. Applied Chem-
istry Division, International Union of Pure and Applied Chemistry have also
been pub] i.shed."'; J
REFERENCES

I. Till NAMIN(; AND INIH'X ING Of· Cfll.MICAL COMPOllNDS FROM CIIEMICAL AIlSI RACfS. Chemi-
cal Ahstracts 5(,: January-Junc. 1962. Suhjcd Indcx.
2. KFNA<;A. E. E. 1966. Commercial and cxrerimental organic insecticides. Bull. Entomol.
Soc. Am. 12: 161.
1. IlI·NSON, W. K. & II. A. ,1ONI.S. 1967. The literature of pesticide chcmistry. J. Assoc. Offic.
Anal. Chemists 51: 22.
 Benson: Chcmi'>try of Pc'>ticidc'> 27
4. SIIII'AI<II. II. II. & .I. N. MAHAN. 1966. U,e of Ag. chemical; continue; to rise. Chern.
and I.n~. New, ;,: X2A.
'). ill NSON. W. R .. N. J. I'AI.MI.~ & T. MORRi·s. Unpublished data on dithiocarbamate pesti-
cide rc~earL'h. ".
6. DAUM. R. J. 1\165. Agricultural and biocidal applications of organometallics. Ann. N. Y.
Acad. Sci. 125: 229.
7. RIEMSCHNEIDER. R. 1963. The chemistry' of the insecticides of the diene group. World
Review of Pest Control 2: 29.
X. ADAMOYIC, V. M. 1966. Aromatic amines as spray reagents in TLC of chlorinated or-
ganic pesticides. J. Chromatog. 2;{: 274.
9a. Ji.NNINGS. B. H. & G. B. HERSCHBACK. 1965. Thc chlorination of camphene. J. ·Org.
Chem. 30: 3'.102.
9b. RICHLY, II. G. JR .. J. E. GRANT. T. J. GARBAClK & D. L. DUll.. 1965. Chlorination
products of camphene. J. Org. Chcm. ;~O: 3909.
10. CAS'I RO, C. E. 1464. The r,'pid oxidation o( porphyrins by alkyl halides. J. An. Chem.
Soc. 116: 2310.
II. CA.S·IRO, E. C. & W. C. KRAY, JR. 1966. The hOlllogeneous reduction or geminal halidt's
by chromous sulfate. J. Am. Chcl1l. '>oc. 1111: 4447.
12. ilANSI.N, K. A. ,9(,'i. Evaluation of wlOlimctric procedure for Dilan. J. Assoc. 0111.:.
Anal. Chemists 411: 774.
13. BROWN, ;1. D. & E. F. ROGLRS. 1950. Insecticidal activity of l,l-dianisylncopcntane.
J. Am. Chcm. Soc. 72: X64.
14. CRISTOI., S. J., N. L. HAUSE & .I. S. MFEK. 1951. Mechanisms of elimination ITaclions.
III. The kinetics of the alkaline dehydrochlorination of BHC i,,'mcrs. J. Am. Chem. Soc.
n: 674.
15. HINI', J., Ie D. WI·.IMA~, JR., P. B. J.AN(;J'(lRD & O. B. RAMSAY. 1966. The mechanisms
of the dehydrochlorination of {j-benzcne hexalhloride. J. Am. Chem. St'C 88: 5522.
16. Cox, J. R. & O. B. RAMSAY. 1964. Mechanisms of nucleophilic substitution in phosphate
esters. Chem. Rev. 64: 317.
17. EI.-RI·I AI, A. R. & I.. GILI'FRIDA. 1965. Separalion and micro quantitative determination
of Dipterex and ODVP by GLC. J. Assoc. Offic. Anal. Chemists ·18: 374.
IX. BI.Ns(JN, W. R. & E. PAPPAS. 1967. Carbamylation with carbamate insecticides and methyl
isocyanate. Sixth Intcrnational Plant Protection Congl",s. Vienna, Austria.
19. BFI';SON, W. R. & R. GAlAN. 1966. Nitrosation of I-naphthyl-N-methylcarbamate and re-
lated compounds as it was followed by oscillopolarography. J. Org. Chem. 31: 2498.
20. 'KRISHNA, J. G., H. W. DOROUGH & J. E. CASIDA. 1962. Radinlabellcd insecticides, syn-
thesis of N-methylcarbamates via methyl isocyanate C'" and chromatographic purifica-
tion. J. Agr. Food Chem. 10: 462.
21. DAMICO, J. & W .. R. BI·N50N. 1965. Mass spectra of some carbamate pe'iticides. J. Assoc.
Ollic. Anal. Chemists 48: 344.
22. CROSIlY, O. G., E. Lr.rns & W. L. WINTERLlN(;. 1965. The photodecomposition of car-
hamate inseclicides. J. Agr. Food Chcm. 13: 204.
23. CHieN, J. T., W. R. 1.l1·.NS()N & N. J. PALMER. 1967. Unpuhlisht'd data on solid slate
photolysis.
24. BI,NSON, W. R., B. KA<;AN, E. LUSHI;, J. T. CllFN & J. SHIJI MAN. 1967. Selective car-
bamylati"'l wilh methyl isocyanate . .I. Org. Chelll. ;~2: 3635.
25. 1l()IHJWSKI. G. & l. SIIAYII., ll!. 1967. The reaction of isocyanates with o-hydroxy aro-
matic aldehyd(,s. J. Org. Chem. ;~2: 953.
26. I.IIS·II(" E., W. R. IlI'NS()N & N. Duy. 1967. Hindered rotation ir N,N-dimcthylcar·
hamates. J. Org. Chcm. ;~2: !l51.
27. CIII·.N, J. T. & W. R. IlI-.Nsfl/<. 1966. Characteristic infrarcd absorption spectra and fre-
quencies of carb~mate pc,ticides. J. Assoc. Ollie. Anal. Chemists ,l9: 412.
2M. WINH.RINIOIIAM, F. 1'. W., A. HARRISON, R. (j. IlRIIl(;I'S & P. M. BRlI>l;I'S. 1955. The fatt'
of lahellcd illsecti~ide rcsidues in food products. I I. The nalure Lf methyl bromide
residucs in fumigated whe'll. J. Sci. Food and Agr. (" 251.
24. BRlIlld,S, R. (j. 14'iS. N-melhylation as a result of fumigating whcat with mcthyl bro-
midc. J. Sci. hlOd and Agr. (" 261. .
30. RAI;U.IS, E. 1' .. B. S. l-'iSHLR & B. A. KI.IMI'CK. 1966. Notc on detcrmination of chloro-
hy·Jrins in food fumigated with ethylene oxide and propylcne oxide. J. Assoc. Offic.
An~1. Chemists 49: '163'.
31. I·RII·.IlMAN, M., J. F. CAY INS & J. S. WALl .. 1965. Relative nucleophilic rcactivities of
amino grollps and mer~"ptide ions in addition reactions with IX, l"i-unsaturated com-
pounds. J. Am. Chem. Soc. 117: 3672.
32. WII.I.IAMS, S. & J. W. COOK. 1967. Pe,ticide rc,idues. Anal. Chern. 39: 142R.
28 Annals New York Academy of Sciences
13. ACRFE, F. JR., M. C. BOWMAN & M. BEROZA. 1963. Co-distillation of DDT with water.
J. Agr. Food Chem. ]]: 278.
14. B.JRKE, J. A. & W. HOLSWADE. 1966. A gas chromatographic column for pesticide resi-
due analysis: Retention times and response data. J. Assoc. Ollic. Anal. Che:11ists 49: 374.
"15. SnlRHERR, R. W., M. E. GETZ, R. R. W~TTS, S. J. ['RIEDMAN, F. ERWIN, L. GIUFFRIDA &
F. IVES. 1964. Identification and analyses of five organophosphatc pcsticides: Recov-
eries from crops fortified at different levels. J. Assoc. Offic. Anal. Chemists 47: 1087.
36. YIP, G. 1964. Paper chromatographic analysis of chlorophenoxy acids and esters in whea;.
J. Assoc. Offic. Anal. Chemists 47: 343.
37. FINOCCHIARO, J. M. & W. R. BENSON. 1967. TLC for some carbamate and phenylurea
pesticides. J. Assoc. Offic. Anal. Chemi,ts 50: 888.
38. MENZIE, C. 1966. Metabolism of pesticides. Special Sci. Report, Wildlife No. 96. U.S.
Dept. of Interior, Washington. D. C.
39. BARON, R. L. & J. DOHERTV. 1967. Metabolism and excretion of an insecticide (6-chloro-
3.4-dimethylphenyl N-methylcarbamate) in the rat. J. Agr. Food Chem. IS: 830.
40. KORTE. F. & H. ARENT. 1965. Metabolism of in,ecticldes. IX. holation and identiflcation
of dieldrin after oral administration of dic1drin-C". Life Sciences 4: 2017.
41. SHEPARD, H. H. 1966. Thc Pesticide Review. U.S. Dept. of Agriculture, Washington,
D.C.
42. KEARNFV. P. & D. KAUFMAN. 1969. Degradation of Herbicides. : 400. M. Dekker, Inc.,
New York, N. Y.
43. JACOBSON, M. 1965. Insect Sex Attractants. lnter-,cience Publi,he", Inc. New York,
N.Y.
44. BORKOVEC, A. B. 1966. Insect chemosterilants. Tn Advances in Pest Control Research,
Vol. VII. E. L. Metcalf, Ed. Interscience Puhlishers. Inc. New York, N. Y.
45. Symposium on Organophosphorus Pe,ticides. American Chemical Society. 153rd Meeting.
Miami, Fla. April 10- 14, 1967.
46. NAIIONAI. ACADEMV OF S('IENCES. Principles of Plant and Animal Pest Control. Vol. 1-6.
I (196R), Il (1968), III (1969), IV (196H), V (not yet scheduled) VI (196H). U. S.
Gov'!. Printing Office. Washington, D. C. )
47. FOOD AND DRUG ADMINISTRAIION. Pe,ticide Analytical Manual. 1968. (Revised) Vol. I.
Method, Which Detect Multiple Residues. Vol. II. Methods Which Detect Individual
Pe'iticide Re .. idues. U. S. Gov't. Printing Office. Washington, D. C.
4~. HODGSON. E., Ed. 1968. Enzymatic Oxidations of Toxicants: 229. North Carolina State
University, Raleigh, N. C.
49. YUI.[, W. N., M. CH!BA & H. V. MORLEV. 1967. Fate of insecticide residues. Decom-
po .. ition of lindane in soil. J. Agr. Food Chem. 15: 1000.
50. H.LGEIA(i. G, & H. TEICHMANN. 1965. The alkylating properties of alkyl thiophosphates.
Angew. Chern. Intern. Edit. 4: 914.
51. O·BRIEN. R. D. 1967. Insecticides: 332. Academic Press. Inc. New York, N. Y.
52. TORGESON, D. C. 1967. Fungicides. Vol. I: Agricultural and Industrial Applications;
Environmental Interactions. Vol. Ii: Chemistry and Physiology. Academic Press, Inc.
New York, N. Y.
5:1. KEITH, L. II .. A. W. GARRISON & A. L. ALfORD. 196M. The high resolution NMR
spectra of pesticides. I. Organophosphorus pesticides. J. Assoc. omc. Anal. Chemists
51: 1063.
54. KU'JIf, L. H. 19"H. High resolution NMR spectra of pC'itiddcs. II. The DDT clas •.
Ah,t.ract of paper No. 49. A",,~iati()n of ()lIidal Anlllytical Chcmi'ito;. 82n<1 Annual
Mcetin/.(. Oct. 14-17. Washlllj.(ton, 1>. C.
<5 KI llH, CII. 1<)6'1. Privale UlmllHJnicatioll.
~Ii. E(;AN, H. 1967, IlJ6H, II}(,<). IUI'AC COlllmi"i{)f1 011 the dcv<,lopnwl1t. improvement. and
,tandardintion of methods of pcsti~ide lc,idllC analysi-; IUPAC ('ull1missioll on ter-
minal residues. J. A"oc. Ollie. Anal. Chemists 50: 1067· 1071; 51: .165 .172; 52: 299-306.

DISCUSSION OF THE PAPER

D. MACDOUGALL (Chemagro Corp., Kansas City, Mo.): I hope that in the

total discussion of pe,ticides this week you will bear in mind that chlorinated
hydrocarbon insecticides represent about 30 per cent of the total amount of the
pesticides used in this country. Some people are very inclined to forget this and
indict all pesticides on the basis of evidence based only on the chlorinated hydro-
carbon in,ecticides.
 Benson: Chemistry of Pesticides 29
Dlt. BIN..,ON: Dr. MacDougall j~ "IN)lulcly (';orrc(';\. However, Dr. Kraybill
wrolc "II of lite ... peaker, a,king whal (,;ol11pound, would be covered at this par-
ticular (;onfcrem:e, and Iho~e people who replied had their particular compounds
mentioned in my paper and the handouts, with the exception of chemicals not
used commercially as pe,ticides.