Chemical Properties
yellow to off-white powder
Definition
ChEBI: A dicarboximide that captan in which the trichloromethyl group is replaced by a 1,1,2,2-tetrachloroethyl group. A broad-spectrum fungicide used to control diseases in fruit and potatoes, it is no longer approved for use in the European Community.
Uses
Agricultural fungicide, especially for potatoes.
General Description
White crystalline solid with a slight, but pungent odor. Mp: 162°C. Practically insoluble in water. Only slightly soluble in organic solvents. Technical CAPTAFOL is a wettable light tan powder that is used as a fungicide. Inhaled dust irritates the respiratory tract. Irritates skin and damages eyes. Acute oral toxicity in humans is low. Not persistent in the environment (decomposes with a half-life of 11 days in the soil). Highly toxic to fish and other aquatic organisms.
Reactivity Profile
CAPTAFOL is non-flammable but, on heating, may decompose to generate toxic fumes, such as sulfur oxides, hydrogen sulfide, hydrochloric acid, and phosgene. Stable at room temperature when dry but readily hydrolysed, especially in an alkaline environment. CAPTAFOL and mixtures containing high concentrations of CAPTAFOL may react violently with alkali. Incompatible with acids, acid chlorides, acid anhydrides, and strong oxidizing agents. Sulfhydryl compounds such as glutathione and cysteine cause a rapid chemical decomposition.
Potential Exposure
Captafol is a thiophthalimide fungicide. Those engaged in the manufacture, formulation, and
application of this fungicide. Captafol is not currently registered for use on field crops or stored produce in the
United States.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth method if victim
ingested or inhaled the substance; give artificial respiration with the aid of a pocket mask equipped with a one-way
valve or other proper respiratory medical device.
Administer oxygen if breathing is difficult. Remove and
isolate contaminated clothing and shoes. In case of contact
with substance, immediately flush skin or eyes with running water for at least 20 minutes. For minor skin contact,
avoid spreading material on unaffected skin. Keep victim
warm and quiet. Effects of exposure (inhalation, ingestion,
or skin contact) to substance may be delayed. Ensure that
medical personnel are aware of the material(s) involved
and take precautions to protect themselves. Medical observation is recommended for 24 to 48 hours after breathingoverexposure, as pulmonary edema may be delayed. As
first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a drug or other inhalation therapy.
Shipping
UN2811 Toxic solids, organic, n.o.s., Hazard
Class: 6.1; Labels: 6.1-Poisonous materials, Technical
Name Required. UN 2773 Phthalimide derivative pesticides, solid, toxic, Hazard Class: 6.1; Labels: 6.1-Poisonous
materials, Technical Name Required.
Incompatibilities
Reacts violently with bases, causing fire
and explosion hazard. Not compatible with strong acids or
acid vapor, oxidizers. Strong alkaline conditions contribute
to instability. Attacks some metals.
Waste Disposal
Hydrolysis.
Hazard
Absorbed by skin. Probable carcinogen.
Agricultural Uses
Fungicide: Captafol is a General Use Pesticide and used for the control of practically all forms of fungal diseases except powdery mildew. It is also used as a seed protectorant on cotton, rice and peanut crops. Not registered for use in the U.S. or in EU countries. There are 20 global suppliers.
Trade name
CAPTATOL®; CAPTOFOL®; CRISFOLATAN®; DIFOLATAN®[C]; DIFOCAP®[C]; DIFOSAN®; FOLCID®; HAIPEN®; KENOFOL®; MERPAFOL®; ORTHO® 5865[C]; PILLARTAN®; SANSEAL®; SANSPOR®; SANTAR-SM®; SULFONIMIDE®; SULPHEIMIDE®
Carcinogenicity
Captafol is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals and supporting data on mechanisms of carcinogenesis.
Environmental Fate
The primary toxicity following captafol exposure probably
occurs through a hypersensitivity mechanism. Most experiments
suggest captafol to be DNA active.
Metabolic pathway
Captafol contains an unstable tetrachloroethylthio (sulfenyl) moiety that
has been shown to undergo rapid hydrolytic and metabolic degradation
to tetrahydrophthalimide (2). By analogy with captan, presumably the
tetrachloroethylthio moiety can be transferred to the sulfur atoms of
thiols such as cysteine and glutathone. Thus in the presence of thiols
such as glutathione, captafol is probably cleaved at the N-S bond to
form thiophosgene (3) and other gaseous products such as hydrogen
sulfide, hydrogen chloride and carbonyl sulfide. Thiophosgene is rapidly
hydrolysed by water. The tetrachloroethylthio group and thiophosgene
are believed to be intermediates in the formation of thiazolidine-2-
thione-6carboxylic acid (4) which is an addition product with cysteine. A
thiazolidine derivative of glutathione is also formed (5). Biotransformation
of captafol in mammals generates primarily thiophosgene (3)
and tetrahydrophthalimide (2). Tetrahydrophthalimide (2) and various
of its derivatives are excreted in the urine. There were no reports of
2-thiazolidinethione-4-carboxylic acid (4) in the urine.
storage
Color Code—Green: General storage may be used.Prior to working with captafol you should be trained on itsproper handling and storage. Store in tightly closed containers in a cool, well-ventilated area away from heat, acids,acid fumes, or strong oxidizers (such as peroxides, chlorates, perchlorates, nitrates and permanganates), since violent reactions occur. A regulated, marked area should beestablished where this chemical is handled, used, or storedin compliance with OSHA Standard 1910.1045.
Degradation
Captafol is hydrolysed rapidly in acidic and alkaline conditions. It
decomposes slowly at its melting point of 161 °C (PM). Captafol is
decomposed by base-catalysed hydrolysis with half-lives of 77.8, 6.54 and
0.72 hours at pH 3,7 and 8, respectively (Kim et al., 1997)
In a study of aqueous photodegradation, a solution (MeCN/H2O 9:l)
of unlabelled captafol (10 g l-1) was exposed to UV light for 4 days. The
reaction tube was encircled by low pressure Hg lamps giving more than
85% of total radiation at 253.7 nm. Pure nitrogen was bubbled through the
solutions. Photo-oxidation studies were done similarly except that oxygen
was bubbled through the solution. In further experiments, irradiation was
by visible light from a tungsten lamp and again oxygen was bubbled
through the solution. The outlet gases from the UV study were trapped in
sodium hydroxide solution and analysed by GC-MS. The main photoproduct
was usually tetrahydrophthalimide (2). Analysis was by chromatography
and IR and NMR spectroscopy. Photolysis under nitrogen gave
2 in 72% yield with elemental sulfur and HCl as the only products other
than some parent captafol. Photooxidation of captafol gave tetrahydrophthalimide
(2) in 78% yield together with sulfur dioxide, carbon dioxide,
hydrogen chloride and some unreacted captafol. Oxidation of captafol
in the presence of visible light together with Rose Bengal as a photosensitiser
also gave a high yield of tetrahydrophthalimide (2) and the
other products obtained from photo-oxidation. Although the mechanisms
of reaction were not studied, it is possible that sulfoxidised intermediates
could be involved in reactions with singlet oxygen. It was surprising that the cyclohexene moiety did not react with singlet oxygen and that
products of ring oxidation were not observed (Crank and Mursyidi, 1992).
Toxicity evaluation
Captafol is not persistent in the environment. Captafol is stable
under ordinary environmental conditions and rapidly degrades
in soil, the rate of degradation being a function of soil type and
pesticide concentration. It does not leach from basic soils and is
unlikely to contaminate groundwater. Captafol sprayed on
most crops has a half-life of less than 5 days. Captafol and/or its
metabolites and degradation products are readily absorbed by
roots and shoots of plants. If released to air, an extrapolated
vapor pressure of 8.27×10-9 mm Hg at 25°C indicates
captafol will exist solely in the particulate phase in the ambient
atmosphere. Particulate-phase captafol will be removed from
the atmosphere by wet and dry deposition. If released to soil,
captafol is expected to have slight mobility based on Koc values
of 2073 and 2120. Volatilization from moist soil surfaces is not
expected to be an important fate process based on a Henry’s
Law constant of 2.7×10-9 atm-cu m mol-1. In a laboratory
setting, the biodegradation half-life of captafol in three soils
was found in the range of 23–55 days. The overall half-life of
captafol in soil is about 11 days, independent of soil type or
initial concentration. If released into water, captafol is expected
to adsorb to suspended solids and sediment based on the Koc.
Volatilization from water surfaces is not expected to be an
important fate process based on this compound’s estimated
Henry’s Law constant. An estimated bioconcentration factor of
170 suggests the potential for bioconcentration in aquatic
organisms is high, provided the compound is not altered
physically or chemically after being released to the environment. The half-lives for the hydrolysis of Difolatan at
pH 3.0, 7.0, and 8.0 were 77.8, 6.54, and 0.72 h, respectively.
Hydrolysis is likely to be the predominant pathway of degradation
in the aquatic environment.
