2,6-Dichlorobenzonitrile

Chemical properties

2,6-Dichlorobenzonitrile [1194-65-6], 1- cyano-2,6-dichlorobenzene, Mr 172.02, mp 144.5 –146.5 ℃, is a colorless, crystalline substance. Its solubility in water is 10 ppm at 25℃. 2,6-Dichlorobenzonitrile is produced industrially by the ammoxidation of 2,6-dichlorotoluene. In addition the nitrile is obtained by oxidation or side-chain-chlorination of 2,6-dichlorotoluene via 2,6-dichlorobenzoic acid and 2,6-dichlorobenzaldehyde, respectively. 2,6-Dichlorobenzonitrile shows herbicidal activity (Casoron, Duphar) and is used in fruit and vine cultivation. It is also used as an intermediate in the production of 2,6-difluorobenzonitrile and of 2,6-dichlorothiobenzamide (Prefix, Shell) which shows herbicidal activity.

The Uses of 2,6-Dichlorobenzonitrile

2,6-dichlorobenzonitrile in which Q-amino-G- chlorobenzonitrile is used as starting material. And it is used for the synthesis of diclofenac sodium oxacillin and guanabenz acetate.

The Uses of 2,6-Dichlorobenzonitrile

Herbicide.

The Uses of 2,6-Dichlorobenzonitrile

Soil-applied herbicide used to control many annual and perennial broad-leaved weeds.

Definition

ChEBI: A nitrile that is benzonitrile which is substituted by chlorines at positions 2 and 6. A cellulose synthesis inhibitor, it is used as a pre-emergent and early post-emergent herbicide.

Synthesis Reference(s)

Synthetic Communications, 20, p. 2785, 1990 DOI: 10.1080/00397919008051490
Synthesis, p. 943, 1992 DOI: 10.1055/s-1992-26271

General Description

2,6-Dichlorobenzonitrile is a white solid dissolved or suspended in a water-emulsifiable liquid carrier. The primary hazard is the threat to the environment. Immediate steps should be taken to limit spread to the environment. Can easily penetrate the soil and contaminate groundwater and nearby streams. Can cause illness by inhalation, skin absorption and/or ingestion. Used as a herbicide.

Air & Water Reactions

Not soluble in water.

Reactivity Profile

A halogenated nitrile. Nitriles may polymerize in the presence of metals and some metal compounds. They are incompatible with acids; mixing nitriles with strong oxidizing acids can lead to extremely violent reactions. Nitriles are generally incompatible with other oxidizing agents such as peroxides and epoxides. The combination of bases and nitriles can produce hydrogen cyanide. Nitriles are hydrolyzed in both aqueous acid and base to give carboxylic acids (or salts of carboxylic acids). These reactions generate heat. Peroxides convert nitriles to amides. Nitriles can react vigorously with reducing agents. Acetonitrile and propionitrile are soluble in water, but nitriles higher than propionitrile have low aqueous solubility. They are also insoluble in aqueous acids.

Health Hazard

SOLID: Harmful if swallowed.

Fire Hazard

Not flammable.

Flammability and Explosibility

Non flammable

Agricultural Uses

Herbicide: Dichlobenil is a herbicide used on cranberry bogs, dichondra, ornamentals, blackberry, raspberry, and blueberry fields, apple, pear, filbert and cherry orchards, vineyards, hybrid poplar-cottonwood plantations, and rights-of-way to control weeds; and sewers to remove roots. It acts on dandelion, prickly oxtongue (pre-emergence), and tree roots. Not approved for use in EU countries. Actively registered in the U.S.

Trade name

BARRIER®; BH Prefix D®; CARSORON®; CASORON® 133; CARSORON® G; CARSORON® G4; CARSORON® G20-SR; CODE H 133®; DECABANE®; DU-SPREX®; DYCLOMEC®; FYDULAN; FYDUMAS; FYDUSIT; H 133®; H 1313®; NIA 5996®; NIAGARA® 5006; NIAGARA 5,996; NOROSAC®; PREFIX D®

Environmental Fate

Biological. A cell suspension of Arthrobacter sp., isolated from a hydrosol, degraded dichlobenil to 2,6-dichlorobenzamide (71% yield) and several unidentified water soluble metabolites (Miyazaki et al., 1975). This microorganism was capable of rapidly degrading dichlobenil in aerobic sediment-water suspensions and in enrichment cultures (Miyazaki et al., 1975).
Soil. The major soil metabolite is 2,6-dichlorobenzamide which undergoes further degradation to form 2,6-dichlorobenzoic acid. The estimated half-lives ranged from 1 to 12 months (Hartley and Kidd, 1987). Under field conditions, dichlobenil persists from 2 to 12 months (Ashton and Monaco, 1991). The disappearance of dichlobenil from a hydrosol and pond water was primarily due to volatilization and biodegradation. The time required for 50 and 90% dissipation of the herbicide from a hydrosol were approximately 20 and 50 days, respectively (Rice et al., 1974). Dichlobenil has a high vapor pressure and volatilization should be an important process. Williams and Eagle (1979) found that the half-life of dichlobenil was 4 weeks in soil 4–8 weeks after application. After 1 year following application, the half-life increased to 1 year.
Plant. In plants, dichlobenil is transformed into glucose conjugates, insoluble residues and hydroxy products that are phytotoxic (Ashton and Monaco, 1991). These include three phytotoxic compounds, namely 2,6-dichlorobenzonitrile, 3-hydroxy-2,6-dichlorobenzonitrile and 4-hydroxy-2,6-dichlorobenzonitrile (Duke et al., 1991). Massini (1961) provided some evidence that dichlobenil is metabolized by plants. French dwarf beans, tomatoes, gherkin and oat plants were all exposed to a saturated atmosphere of dichlobenil at room temperature for 4 days. Most of the herbicide was absorbed and translocated by the plants in 3 days. After 6 days of exposure, bean seedlings were analyzed for residues using thinlayer plate chromatography. In addition to dichlobenil, another compound was found but it was not 2,6-dichlorobenzoic acid (Massini, 1963).
Surface Water. The time required for 50 and 90% dissipation of the herbicide from New York pond water was approximately 21 and 60 days, respectively (Rice et al., 1974).
Photolytic. When dichlobenil was irradiated in methanol with a 450-W mercury lamp and a Corex filter for 8 hours, o-chlorobenzonitrile and benzonitrile formed as the major and minor products, respectively (Plimmer, 1970).
Chemical/Physical. Dichlobenil is hydrolyzed, especially in the presence of alkali, to 2,6-dichlorobenzamide (Briggs and Dawson, 1970; Worthing and Hance, 1991). Emits toxic fumes of nitrogen oxides and chlorine when heated to decomposition (Sax and Lewis, 1987).

Metabolic pathway

Twelve metabolites are isolated from either urine or bile from either rats (11 metabolites) or goats (seven metabolites) given single oral doses of 14C-labeled 2,6-dichlorobenzonitrile (DCBN). Five of these metabolites are also excreted in urine from rats dosed orally with 2,6-dichlorothiobenzamide (DCTBA) which is an acid amide analog. All metabolites from either DCBN or DCTBA are benzonitriles with the following ring substituents: Cl2, OH (three isomers); Cl2, (OH)2; Cl, (OH)2; Cl, OH, SH; Cl, OH, SCH3; SOCH3, OH; Cl2, S-(N-acetyl)cysteine; Cl, S-(N-acetyl)cysteine; Cl, OH, S-(N-acetyl)cysteine.
The thiobenzamide moiety of DCTBA is converted to the nitrile in all extracted urinary metabolites. No hydrolysis of the nitrile in DCBN to either amide or an acid is detected. Urine is the major route for excretion; however, enterohepatic circulation occurs.

Purification Methods

Crystallise the nitrile from acetone. [Beilstein 9 IV 1006.]