Cycluron

Herbicides

Active substance -> EU Pesticides database: Not approved

Pesticides -> Herbicides, Urea Derivative

SOLUBILITY @ 20 °C: 1.1 G/L WATER, 67 G/KG ACETONE, 55 G/KG BENZENE, 500 G/KG METHANOL

In water at 20 °C, 0.11%. In acetone 6.7%, benzene 5.5%, methanol 50%, ethyl acetate 4.4 g/100g, diethyl ether 1.6g/100g (all at 20 °C).

In water 1.2X10+3 mg/l at 20 °C

138 °C (PURE)

MP: 134-138 °C /Technical/

0.0000667 [mmHg]

1X10-7 MM HG @ 20 °C

Warning

H302 (100%): Harmful if swallowed [Warning Acute toxicity, oral]

P264, P270, P301+P317, P330, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 39 reports by companies from 1 notifications to the ECHA C&L Inventory.

SRP: At the time of review, criteria for land treatment or burial (sanitary landfill) disposal practices are subject to significant revision. Prior to implementing land disposal of waste residue (including waste sludge), consult with environmental regulatory agencies for guidance on acceptable disposal practices.

TERRESTRIAL FATE: In soil ... demethylation of the nitrogen atom, hydrolytic cleavage, and liberation of carbon dioxide and ammonia /occurs/.

TERRESTRIAL FATE: Based on a recommended classification scheme(1), estimated Koc values ranging from 88 to 160(SRC), determined from an experimental water solubility of 1200 mg/l(2) and a structure estimation method(3), indicate that cycluron is expected to have moderate to high mobility in soil(SRC). Volatilization of cycluron from moist soil surfaces is not expected given an estimated Henry's Law constant of 1.2X10-8 atm-cu m/mole(SRC), using a fragment constant estimation method(4). Cycluron is not expected to volatilize from dry soil surfaces based on an estimated vapor pressure of 2.6X10-5 mm Hg(SRC), determined from a fragment constant method(5). Cycluron had a mobility factor of 3.8 in Hagerstown silty clay loam(4.3% organic matter, 30% clay, pH 5.5) and 4.3 in Lakeland sandy loam(3.3% organic matter, 10% clay, pH 6.2) soil columns(6). Mobility factors of 1 and 6 indicate no movement and maximum movement in the soil column, respectively(6). A 50% decrease in degradation of the urea herbicide, diuron, after soil sterilization(7) indicates that microorganisms may be important in the transformation of cycluron(SRC). The soil persistence of cycluron was reported as 4.5 to 60 weeks at doses of 0.125 to 2.0 lb/acre, based on the time taken for its activity to decrease below levels giving 50% and 20% growth inhibition in Italian ryegrass(8).

AQUATIC FATE: Based on a recommended classification scheme(1), estimated Koc values ranging from 88 to 160(SRC), determined from an experimental water solubility of 1200 mg/l(2) and a structure estimation method(3), indicate that little adsorption to suspended solids and sediment in water is expected for cycluron(SRC). Cycluron is not expected to volatilize from water surfaces based on an estimated Henry's Law constant of 1.2X10-8 atm-cu m/mole(SRC), developed using a fragment constant estimation method(5). According to a classification scheme(6), estimated BCF values ranging from 11 to 79(4,SRC), determined from an experimental water solubility of 1200 mg/l(2) and an estimated log Kow of 2.8(7,SRC), suggest that bioconcentration in aquatic organisms is low to moderate, not high(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), cycluron, which has a vapor pressure of 1X10-7 mm Hg at 20 °C(2), is expected to exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase cycluron is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be about 15 hours(3,SRC). Particulate-phase cycluron may be physically removed from the air by wet and dry deposition(SRC).

Koc = 93 (calculated from water solubility by regression equations). /From table/

Using a structure estimation method based on molecular connectivity indices(1), the Koc for cycluron can be estimated to be about 160(SRC). According to a recommended classification scheme(2), this estimated Koc value suggests that cycluron is expected to have moderate mobility in soil(SRC). An estimated Koc value of 88(3,SRC) was calculated from a measured water solubility of 1200 mg/l at 20 °C(4). According to a recommended classification scheme(2), this estimated Koc value suggests that cycluron is expected to have high mobility in soil(SRC).

... Some plants such as cotton are able to degrade herbicidal ureas relatively rapidly to nonphytotoxic compounds. /Ureas/

Urea herbicides readily undergo photolysis. /Urea herbicides/

A decrease in degradation of urea herbicides after soil sterilization was observed; approx. 30% of diuron was degraded after 4 weeks in nonsterilized soil samples, <15% of diuron was degraded after 4 weeks in sterile soil(1). The soil persistence of cycluron was reported as 4.5 to 60 weeks at doses of 0.125 to 2.0 lb/acre, based on the time taken for its activity to decrease below levels giving 50% and 20% growth inhibition in Italian ryegrass(2).

Bioconcentration factor = 12 (calculated from water solubility by regression equations). /From table/

An estimated BCF value of 79 was calculated for cycluron(SRC), using an estimated log Kow of 2.8(1,SRC) and a recommended regression-derived equation(2). According to a classification scheme(3), this BCF value suggests that bioconcentration in aquatic organisms is moderate, not high(SRC). An estimated BCF value of 11 was calculated for cycluron(SRC), using an experimental water solubility of 1200 mg/l at 20 °C(4,SRC) and a recommended regression-derived equation(2). According to a classification scheme(3), this BCF value suggests that bioconcentration in aquatic organisms is low(SRC).

The Henry's Law constant for cycluron is estimated as 1.2X10-8 atm-cu m/mole(SRC) using a fragment constant estimation method(1). This value indicates that cycluron will be essentially nonvolatile from water surfaces(2,SRC). Cycluron's Henry's Law constant(1,SRC) indicates that volatilization from moist soil surfaces is not expected (SRC). Cycluron is not expected to volatilize from dry soil surfaces based on an estimated vapor pressure of 2.6X10-5 mm Hg(SRC), determined from a fragment constant method(3).

... THERE WAS NO LOCAL IRRITATION TO THE BACKS AND EARS OF WHITE RABBITS TREATED FOR 24 HR WITH 50% AQ FORMULATION.

Not toxic to bees.

...UREA HERBICIDES /INCL CYCLOURON/ ARE OF VERY LOW TOXICITY TO WARM-BLOODED ANIMALS. ... /UREA HERBICIDES/

The rate constant for the vapor-phase reaction of cycluron with photochemically-produced hydroxyl radicals has been estimated as 2.5X10-11 cu cm/molecule-sec at 25 °C(SRC) using a structure estimation method(1,SRC). This corresponds to an atmospheric half-life of about 15 hours at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1,SRC).

Cycluron's former use as a pre-emergence herbicide will have resulted in its release to the environment. If released to the atmosphere, cycluron is expected to exist in both the vapor and particulate phases in the ambient atmosphere based on vapor pressure of 1X10-7 mm Hg. Vapor-phase cycluron is expected to be degraded by reaction with photochemically produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 15 hours. Particulate-phase cycluron will be removed from the atmosphere by wet and dry deposition. If released to soil, cycluron is expected to have moderate to high mobility based on estimated Koc values ranging from 88 to 160. Volatilization from wet and dry soil surfaces is not expected given an estimated Henry's Law constant of 1.2X10-8 atm-cu m/mole and an estimated vapor pressure of 2.6X10-5 mm Hg, respectively. Degradation in soil is expected to occur(persistence of 4.5 to 60 weeks). If released into water, cycluron is expected to adsorb very little to suspended solids and sediments in water, based on estimated Koc values ranging from 88 to 160. Low to moderate bioconcentration in aquatic organisms is expected based on estimated BCF values ranging from 11 to 79. Volatilization from water surfaces is not expected based on an estimated Henry's Law constant of 1.2X10-8 atm-cu m/mole. Occupational exposure to cycluron may have occurred through inhalation of dusts and dermal contact with this herbicide during its application or at workplaces where cycluron was produced. (SRC)

Their herbicidal activity depends on inhibition of photosynthesis by blocking of electron transport in Photosystem II. /Ureas/

/In photosynthesis/ ... The urea herbicides interfere with the mechanism of oxygen evolution ... A flavin-containing enzyme may be involved in the photosynthetic reaction sequence in which oxygen is produced. Blocking this enzyme by urea results in the destruction of the plant by starvation or as a result of accumulation of a phytotoxic product. /Urea herbicides/

Used formerly as pre-emergence herbicide for onions, spinach, sugar beets, forestry, and other crops; Formerly used in 3:2 formulation with Chlorbufam; Discontinued by BASF sometime before 1985; [HSDB]

Farming (Pesticides) [Category: Industry]

PRE-EMERGENCE HERBICIDE /SRP: FORMER USE/

In combination (3:2) with chlorbufam, pre-emergence herbicidal control of annual weeds in onions, peas, beans, and spinach. Also used in forestry, on seed beds before planting out and on beds for transplanting vegetables (restricted use). /SRP: Former use/

Use ... for pre-emergence weed control in ... spinach. /SRP: Former use/

CYCLURON IS USED IN 3:2 MIXTURE WITH CHLORBUFAM AS A PRE-EMERGENCE HERBICIDE @ 3-6 L 'ALIPUR'/HECTARE FOR CONTROL OF ANNUAL WEEDS IN SUGAR BEET AND SEVERAL VEGETABLE CROPS. /SRP: FORMER USE/

BY REACTION OF CYCLO-OCTYLAMINE WITH DIMETHYLCARBAMOYL CHLORIDE

Dry hydrogen chloride is led into a solution of 127 parts of cyclooctylamine in 410 parts of dry dioxane at room temperature until the whole of the amine has been converted into the hydrochloride. Then dry phosgene is led into the solution kept at 90 °C until the color of the solution has changed to yellow-brown, which requires about 2 to 3 hr. After distilling off about 100 parts of dioxane (whereby the excess of phosgene and hydrogen chloride are removed), dimethylamine is led into the solution of the cyclooctyl isocyanate formed at room temperature until it is saturated and the reaction mixture kept at 50 °C for 1 hr after the end of the introduction; it is then allowed to cool and the precipitated 1-cyclooctyl-3,3-dimethylurea is filtered off by suction, suspended in water and after repeated filtration by suction dried in a vacuum drying cabinet at 60 °C. If necessary the compound can be recrystallized from cyclohexane. 168 parts of 1-cyclooctyl-3,3-dimethylurea ... are obtained.

ALIPUR, AN EMULSIFIABLE CONCENTRATE (150 G CYCLURON AND 100 G CHLORBUFAM/L).

... /TRIXABON IS/ COMBINATION OF DIMEXAN, CYCLURON (OMU), AND CHLORBUFAM (BIPC) AS AN EMULSIFIABLE CONCENTRATE, 73.2% WEIGHT/VOLUME ACTIVE INGREDIENTS. /TRIXABON/

HS 61

ALIPUR-O

CYCLURON WAS INTRODUCED IN 1958 BY BASF AG AS COMPONENT OF THEIR HERBICIDE 'ALIPUR', PROTECTED BY DBP (WEST GERMAN PATENT) 1027930; 1062482.

Product discontinued by BASF Aktiengesellschaft.

NITROSATION OF CYCLURON WAS INVESTIGATED IN PRESENCE OF 6 N HCL OR ACETIC ACID @ PH 1 & EXCESS SODIUM NITRITE FOR 4 HR @ 37 °C AND FOUND TO FORM A 7% YIELD OF DIMETHYLNITROSAMINE.

Discontinued name: Alipur (with chlorbufam) (BASF AG)

NITROSATION OF CYCLURON WAS INVESTIGATED IN PRESENCE OF 6 N HCL OR ACETIC ACID @ PH 1 & EXCESS SODIUM NITRITE FOR 4 HR @ 37 °C AND FOUND TO FORM A 7% YIELD OF DIMETHYLNITROSAMINE.