Dichlorprop

Dichlorprop is a chlorophenoxy herbicide similar in structure to 2,4-D that is used to kill annual and perennial broadleaf weeds. It is a component of many common weedkillers. About 4 million pounds of dichlorprop are used annually in the United States.

Dichlorprop

Names
IUPAC name (R)-2-(2,4-dichlorophenoxy)propanoic acid
Other names 2,4-DP
Identifiers
CAS Number	120-36-5 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:75375 Y
ChEMBL	ChEMBL573221 Y
ChemSpider	8120 Y
ECHA InfoCard	100.003.991
EC Number	204-390-5
KEGG	C11020 Y
PubChem CID	8427
RTECS number	UF1050000
UNII	J7YV2RKO6Q Y
UN number	3077 2765
CompTox Dashboard (EPA)	DTXSID0020440
InChI InChI=1S/C9H8Cl2O3/c1-5(9(12)13)14-8-3-2-6(10)4-7(8)11/h2-5H,1H3,(H,12,13) Y Key: MZHCENGPTKEIGP-UHFFFAOYSA-N Y InChI=1/C9H8Cl2O3/c1-5(9(12)13)14-8-3-2-6(10)4-7(8)11/h2-5H,1H3,(H,12,13) Key: MZHCENGPTKEIGP-UHFFFAOYAD
SMILES Clc1cc(Cl)ccc1OC(C(=O)O)C
Properties
Chemical formula	C9H8Cl2O3
Molar mass	235.064 g/mol
Appearance	white solid
Melting point	116 to 120 °C (241 to 248 °F; 389 to 393 K) R-isomer
Boiling point	215 °C
Solubility in water	720 mg/L at 20 °C (R-isomer)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H312, H315, H318
Precautionary statements	P264, P270, P280, P301+P312, P302+P352, P305+P351+P338, P310, P312, P321, P322, P330, P332+P313, P362, P363, P501
Flash point	204 °C (399 °F; 477 K)
Related compounds
Related compounds	2,4-D
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Chemistry

R-dichlorprop (dichlorprop-p)

Dichlorprop possesses a single asymmetric carbon and is therefore a chiral molecule, however only the R-isomer is active as an herbicide. When dichlorprop was first marketed in the 1960s, it was sold as racemic mixture of stereoisomers, but since then advances in asymmetric synthesis have made possible the production of the enantiopure compound. Today, only R-dichlorprop (also called dichlorprop-p or 2,4-DP-p) and its derivatives are sold as pesticides in the United States.

Dichlorprop is a carboxylic acid, and like related herbicides with free acid groups, it is often sold as a salt or ester. Currently, the 2-ethylhexyl ester is used commercially. The butoxyethyl and isooctyl esters were once popular, but are no longer approved for agricultural use. For the salts, the dimethylamine salt is still available, while the diethanolamine salt is no longer used.

According to the United States Environmental Protection Agency (EPA), "2,4-DP-p is thought to increase cell wall plasticity, biosynthesis of proteins, and the production of ethylene. The abnormal increase in these processes result in abnormal and excessive cell division and growth, damaging vascular tissue. The most susceptible tissues are those that are undergoing active cell division and growth."

Health effects

The EPA rates the oral acute toxicity of dichlorprop as "slight" based on a rat LD₅₀ of 537 mg/kg, and its derivatives are even less toxic. It is, however, considered to be a severe eye irritant. There has been concern that chlorophenoxy herbicides including dichlorprop may cause cancer, and in 1987 the International Agency for Research on Cancer (IARC) ranked this class of compounds as group 2B "possibly carcinogenic to humans". The EPA classifies the R-isomer as “Not Likely to be Carcinogenic to Humans.”