2,4-Dichlorophenoxyacetic acid

August 27, 2012
Image of 2,4-Dichlorophenoxyacetic acid 3D Image of 2,4-Dichlorophenoxyacetic acid

2,4-Dichlorophenoxyacetic acid—“2,4-D” to millions of farmers—is one of the most widely used broadleaf herbicides in the world. Its preparation from 2,4-dichlorophenol and chloroacetic acid was reported by R. Pokorny in 1941, and it was developed as a major herbicide during World War II. Recently, EPA, in response to a petition from the Natural Resources Defense Council to ban 2-4D, declared that its approved uses are safe.

MOTW Update

Herbicides glyphosate and 2,4-dichlorophenoxyacetic acid were Molecules of the Week on October 5, 2009, and August 12, 2012, respectively. In October 2014, the US Environmental Protection Agency (EPA) awarded a registration to Dow AgroSciences for Enlist Duo, a combination of these chemicals. But last month the EPA asked a federal court to rescind its approval on the basis that Dow may have understated its toxicity to nontarget plants. Dow believes that EPA’s concerns can be overcome before the start of the 2016 growing season.

The September 9, 2012, molecule was the kinase inhibitor bosutinib. It was notorious at the time because researchers were unwittingly performing studies on a compound labeled as bosutinib, which was in fact one of its isomers. Now Pfizer chemists have developed simple analytical methods that distinguish the drug from its isomers.

MOTW update:
March 7, 2022

Herbicides atrazine1, the Molecule of the Week for May 10, 2010, and 2,4-dichlorophenoxyacetic acid2 both have been heavily used in commercial agriculture for decades and have increasingly come under environmental restrictions.

Now, after many years of neglect, the US Environmental Protection Agency is reassessing the use of these and many other pesticides in terms of their compliance under the Endangered Species Act of 1973. In response, manufacturers and farmers’ groups have complained that the new mitigation measures make it difficult to find alternative products so close to this year’s growing season.

1. CAS Reg. No. 1912-24-9.
2. CAS Reg. No. 94-57-5.

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