2,4,5-Trichlorophenoxyacetic acid

2,4,5-Trichlorophenoxyacetic acid (also known as 2,4,5-T), a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants. It was developed in the late 1940s and was widely used in the agricultural industry until being phased out, starting in the late 1970s due to toxicity concerns. Agent Orange, a defoliant used by the British in the Malayan Emergency and the U.S. in the Vietnam War, was equal parts 2,4,5-T and 2,4-D (2,4-dichlorophenoxyacetic acid). 2,4,5-T itself is toxic with a NOAEL of 3 mg/kg/day and a LOAEL of 10 mg/kg/day.[3] Additionally, the manufacturing process for 2,4,5-T contaminates this chemical with trace amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a carcinogenic persistent organic pollutant with long-term effects on the environment. With proper temperature control during production of 2,4,5-T, TCDD levels can be held to about .005 ppm. Before the TCDD risk was well understood, early production facilities lacked proper temperature controls and individual batches tested later were found to have as much as 60 ppm of TCDD.

2,4,5-Trichlorophenoxyacetic acid

Names
Preferred IUPAC name (2,4,5-Trichlorophenoxy)acetic acid
Other names 2,4,5-Trichlorophenoxyacetic acid 2,4,5-T Trioxone
Identifiers
CAS Number	93-76-5 Y
3D model (JSmol)	Interactive image
Beilstein Reference	2055620
ChEBI	CHEBI:27903 Y
ChEMBL	ChEMBL194458 Y
ChemSpider	1435 Y
ECHA InfoCard	100.002.068
EC Number	202-273-3
Gmelin Reference	434052
KEGG	C07100 Y
PubChem CID	1480
RTECS number	AJ8400000
UNII	9Q963S4YMX Y
UN number	2811 3345 3348 2765
CompTox Dashboard (EPA)	DTXSID5021388
InChI InChI=1S/C8H5Cl3O3/c9-4-1-6(11)7(2-5(4)10)14-3-8(12)13/h1-2H,3H2,(H,12,13) Y Key: SMYMJHWAQXWPDB-UHFFFAOYSA-N Y InChI=1/C8H5Cl3O3/c9-4-1-6(11)7(2-5(4)10)14-3-8(12)13/h1-2H,3H2,(H,12,13) Key: SMYMJHWAQXWPDB-UHFFFAOYAR
SMILES Clc1cc(OCC(=O)O)c(Cl)cc1Cl
Properties
Chemical formula	C8H5Cl3O3
Molar mass	255.48 g/mol
Appearance	Off-white to yellow crystalline solid
Odor	odorless
Density	1.80 g/cm3, 20 °C
Melting point	154 to 158 °C (309 to 316 °F; 427 to 431 K)
Boiling point	decomposes[1]
Solubility in water	238 mg/kg (30 °C)
Vapor pressure	1×10−7 mmHg[1]
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H315, H319, H335, H410
Precautionary statements	P261, P264, P270, P271, P273, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P330, P332+P313, P337+P313, P362, P391, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
LD50 (median dose)	381 mg/kg (guinea pig, oral) 300 mg/kg (rat, oral) 425 mg/kg (hamster, oral) 242 mg/kg (mouse, oral)[2]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 10 mg/m3[1]
REL (Recommended)	TWA 10 mg/m3[1]
IDLH (Immediate danger)	250 mg/m3[1]
Related compounds
Related compounds	2,4-D auxin
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

In 1970, the United States Department of Agriculture halted the use of 2,4,5-T on all food crops except rice, and in 1985, the EPA terminated all remaining uses in the U.S. of this herbicide. In Canada, the use and sale of 2,4,5-T was prohibited after 1985.[4] The international trade of 2,4,5-T is restricted by the Rotterdam Convention. 2,4,5-T has since largely been replaced by dicamba and triclopyr.

Human health effects from 2,4,5-T at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Intentional overdoses and unintentional high dose occupational exposures to chlorophenoxy acid herbicides have resulted in weakness, headache, dizziness, nausea, abdominal pain, myotonia, hypotension, renal and hepatic injury, and delayed neuropathy. Cometabolism of 2,4,5-T is possible to produce 3,5-dichlorocatechol[5] which, in turn, can be degraded by Pseudomonas bacteria.[6] IARC considers the chlorophenoxyacetic acids group of chemicals as possibly carcinogenic to humans.[7] In 1963 a production vessel for 2,4,5-T exploded in the Philips-Duphar plant in the Netherlands.[8] Six workers that cleaned up afterwards got seriously intoxicated and developed chloracne.[8] After twelve years, four of the six cleaners had died.