4-Chlorophenoxyacetic acid (syn: p-Chlorophenoxyacetic acid; 4-CPA) is a chlorophenoxyacetic acid and synthetic plant growth regulator used to mimic the physiological effects of auxin, thus influencing root and fruit growth. It can also be used as a herbicide at high dosage. 4-CPA was registered in the United States in 1969 for use a plant growth regulator for mung beans and later as a fruiting bloom set for tomatoes. 4-CPA has been used in the para-chlorophenoxyacetic acid (p-CPA) residue assay.
4-CPA is soluble in ethanol, KOH and most organic solvents. It is slightly soluble in water but degradation in aqueous medium has been reported. According to the EPA, it also degrades if exposed to sunlight (30% loss in 24 hours).
| Mechanism of Action |
4-CPA mimics the endogenous plant growth regulator auxin thus it can regulate plant cell division, differentiation and gene expression. |
| Microbiology Applications |
4-CPA is metabolized by soil microorganisms into 2-hydroxy-4-chlorophenoxyacetic acid. Additional aromatic intermediates include, 4-Chlorophenol, 4-chlorocatechol, and hydroquinone. Further oxidation of these chloroderivatives then yields stable chloride ions. |
| Plant Biology Applications |
4-CPA is used as a plant growth regulator to improve fruit set in tomatoes, berries, and other fruit. It can also be used for weed control. According to the Environmental Protection Agency, pesticide products containing this compound as an active ingredient and labeled as specified in the Reregistration Eligibility Decision document released in (1997) this compound will not cause unreasonable risk to humans or the environment. 4-CPA can also be used as a plant growth regulator to restrict root growth during mung bean seed germination. |
| References |
Environmental Protection Agency (1997) Reregistration Eligibility Decision (RED) 4-Chlorophenoxy-acetic Acid (4-CPA) EPA 738-R-97-001 Han Y, Yang C, Zhou Y, Han D, Yan H (2017) Ionic liquid-hybrid molecularly imprinted material-filter solid-phase extraction coupled with HPLC for determination of 6-Benzyladenine and 4-Chlorophenoxyacetic acid in bean sprouts. J Agric Food Chem. 65(8):1750-1757 PMID 28147482 Krzysztof Kuśmierek K, Lidia Dąbek L and Andrzej Świątkowski A (2022) Removal of phenoxy herbicides from aqueous solutions using lignite as a low-cost adsorbent. Desalination and Water Treatment, 260:111-118 Liu Z et al (2021) 4-CPA (4-Chlorophenoxyacetic Acid) Induces the Formation and Development of Defective "Fenghou" (Vitis vinifera × V. labrusca) Grape Seeds. Biomolecules. 2021 Mar 30;11(4):515. PMID: 33808413 Moran O, Traverso S, Elia L and Pusch M (2003) Molecular modeling of p-chlorophenoxyacetic acid binding to the CLC-0 channel. Biochem. 42(18):5176-5185 Pernak J et al (2022) Dicationic herbicidal ionic liquids comprising two active ingredients exhibiting different modes of action. J. Agric. Food Chem 70(8):2545-2553 Sidahmed OA and Kliewer WM (1980). Effects of defoliation, gibberellic acid and 4-Chlorophenoxyacetic acid on growth and composition of Thompson seedless grape berries. Am. J. Enol. and Viticult. 31(2):149-153 |
