4.1. CHEMICAL IDENTITY

2,4-D is a free acid, phenoxy herbicide belonging to the phenoxyacetic acid chemical family, which is widely used in the United States. While the free acid is itself used as an herbicide, there are nine forms of 2,4-D registered as active ingredients in end use products. These include salts, amines, and esters of 2,4-D (EPA 2005a). Derivatives include the sodium salt, diethanolamine salt, dimethyl amine salt, isopropylamine salt, triisopropanolamine salt, butoxyethyl ester, ethylhexyl ester, and isopropyl ester. Almost 90–95% of total 2,4-D global use is accounted for by the dimethyl amine salt and ethylhexyl ester (Charles et al. 2001).

Formulations of 2,4-D and its derivatives vary in their chemical properties and behavior in the environment. However, most quantified analyses of 2,4-D and its derivatives are expressed in terms of the free acid (EPA 2005a).

Information regarding the chemical identity of 2,4-D and its derivatives are provided in Tables 4-1 and 4-2, respectively.

Table 4-1

Chemical Identity of 2,4-D.

Table 4-2

Chemical Identity of 2,4-D Derivatives.

4.2. PHYSICAL AND CHEMICAL PROPERTIES

Information regarding the physical and chemical properties of 2,4-D and its derivatives are provided in Tables 4-3 and 4-4, respectively.

Table 4-3

Physical and Chemical Properties of 2,4-D.

Table 4-4

Physical and Chemical Properties of 2,4-D Derivatives.