| 2,4,5-Trichlorophenoxyacetic acid | |
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(2,4,5-Trichlorophenoxy)acetic acid |
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Other names
2,4,5-Trichlorophenoxyacetic acid |
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| Identifiers | |
| CAS number | 93-76-5 |
| ChemSpider | 1435 |
| UNII | 9Q963S4YMX |
| KEGG | C07100 |
| ChEBI | CHEBI:27903 |
| ChEMBL | CHEMBL194458 |
| RTECS number | AJ8400000 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C8H5Cl3O3 |
| Molar mass | 255.48 g mol−1 |
| Appearance | Off-white to yellow crystalline solid |
| Density | 1.80 g/cm³, 20 °C |
| Melting point |
154-158 °C |
| Solubility in water | 238 mg/kg (30 °C) |
| Hazards | |
| R-phrases | 22-36/37/38-50/53 |
| S-phrases | 24-60-61 |
| Related compounds | |
| Related compounds | 2,4-D auxin |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
2,4,5-Trichlorophenoxyacetic acid (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 U.S. in the Vietnam War, was equal parts 2,4,5-T and 2,4-D.
2,4,5-T itself is of only moderate toxicity, with oral LD50 of 389 mg/kg in mice and 500 mg/kg in rats. However, 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 extremely toxic to humans. 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.
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 US of this herbicide. The international trade of 2,4,5-T is restricted by the Rotterdam Convention. 2,4,5-T has since largely been replaced by dicamba and triclopyr.
Apart from agricultural uses, 2,4,5-T was also a major ingredient in Agent Orange, a herbicide blend used by the U.S. military in Vietnam between January 1965 and April 1970 as a defoliant. Because of TCDD contamination in the 2,4,5-T component, it has been blamed for serious illnesses in many veterans who were exposed to it. Agent Orange often had much higher levels of TCDD than 2,4,5-T used in the US.
1. Tschirley FH. Defoliation in Vietnam. Science. 1969;163:779-786.
2. Orians GH, Pfeiffer EW. Ecological effects of the war in Vietnam. Science. 1970;168:544-554.
3. Neilands JB, Orians GH, Pfeiffer EW, Vennema A, Westing AH. Harvest of Death: Chemical Warfare in Vietnam and Cambodia. New York: Free Press; 1972.
4. Gochfeld M. The other victims of the Vietnam war. BioScience. 1975;25:540-541.
5. Westing AH, ed. Herbicides in War. The Long Term Ecological and Human Consequences. London: Taylor and Francis; 1984.
6. Schecter AJ, Tong HY, Monson SJ, Goss ML. Levels of 2,3,7,8-TCDD in silt samples collected between 1985-86 from rivers in the North and South of Vietnam. Chemosphere. 1989;19:547-550.
7. Schecter AJM, Dai LC, Thuy LTB, et al. Agent Orange and the Vietnamese: the persistence of elevated dioxin levels in human tissues. Am J Public Health. 1995;85:516-522.
8. Kahn PC, Gochfeld M, Nyugen M, Hansson M, Rappe C, Velez H. Dioxins and dibenzofurans in blood and adipose tissue of Agent Orange-exposed Vietnam veterans and matched controls. JAMA. 1988;259:1661-1667.
9. Fingerhut MA, Halperin WE, Marlow DA, et al. Cancer mortality in workers exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin. N Engl J Med. 1991;324:212-218.
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