IUPAC name:2,4-dichlorophenoxy acetic acid
ISO name (common): 2,4-D
Molecular Formula:C8H6Cl2O3
Structural Formula:

      H        H
       \      /
        C == C     H OH
       /      \    | |  
   Cl-C        C-O-C-C=O
       \\    //    |
        C -- C     H
       /      \
      H       Cl

Molecular Mass: 221.0
CAS number: 94-75-7
Melting point:139.25°C
Appearance: Off-white crystalline powder, slight phenolic odour

Rat LD50oral: 425-764mg/kg
Rat LD50dermal: >2000mg/kg
Rat LD50inhalation: 1.79mg/l (4 hour exposure)

Carcinogenicity: No evidence of carcinogenic properties
Neurotoxicity: Neurotoxic at high concentrations (reversible)

2,4-D was the first successful selective herbicide to be developed. First marketed in 1946 it quickly became the most widely used agricultural herbicide. Even 56 years after its introduction it is still the third most widely used herbicide in the US and Canada.

When mixed in a 50:50 ratio with 2,4,5-T it forms Agent Orange the infamous defoliant used in the Vietnam conflict by the US military.

It is used to control weeds on wheat and small grains, sorghum, corn, rice, sugar cane, low-till soybeans, rangeland, and pasture. It is also used on rights-of-way, roadsides, non-crop areas, forestry, lawn and turf care, and on aquatic weeds.

The widespread usage of 2,4-D can be demonstrated by sampling soil bacteria from almost anywhere. A number of organisms will grow in 2,4-D enriched media, and HPLC of the spent media shows that these organisms breakdown 2,4-D as a carbon source.

Development of bioremediation techniques including the refinement of Burkholderia cepacia strain H1 are ongoing. The aim is to be able to remove 2,4-D from contaminated water and soil.

Review report for the active substance 2,4-D. European Commission, Health and Consumer Protection Directorate, Oct 2001