Title: Maleic Hydrazide
CAS Registry Number: 123-33-1
CAS Name: 1,2-Dihydro-3,6-pyridazinedione
Additional Names: maleic acid hydrazide; MH
Trademarks: Fazor; Malazide; Regulox
Molecular Formula: C4H4N2O2
Molecular Weight: 112.09
Percent Composition: C 42.86%, H 3.60%, N 24.99%, O 28.55%
Literature References: Prepd by treating maleic anhydride with hydrazine hydrate in alcohol: Arndt et al., C.A. 43, 579 (1949); see also Curtius, Foerstinger, J. Prakt. Chem.  51, 391 (1895). From maleic acid and a hydrazine salt of a strong inorganic acid: Harris, Schoene, US 2575954 (1951 to U.S. Rubber). Alternate prepn from hydrazine sulfate and maleic anhydride in aqueous NaOH: Amatsu, Karasawa, C.A. 51, 18014c (1957); from hydrazine hydrate and maleic anhydride in glacial acetic acid: Feuer et al., J. Am. Chem. Soc. 80, 3790 (1958). Has the ability to inhibit growth of plants without killing them: Schoene, Hoffmann, Science 109, 588 (1949). Toxicity data: R. Ben-Dyke et al., World Rev. Pest Control 9, 119 (1970). Review: Massey, Manuf. Chem. 26, 197-200 (1955). Review and chromatographic studies: Fishbein, Chromatography of Environmental Hazards (Elsevier, New York, 1972) pp 161-166. Review of toxicology: R. Ponnampalam et al., Regul. Toxicol. Pharmacol. 3, 38-47 (1983).
Properties: Crystals from water, dec 260°. Also reported as mp >300° (Feuery). Slightly sol in hot alcohol, more sol in hot water. LD50 orally in rats: 3800-6800 mg/kg; dermally in rabbits: >4000 mg/kg (Ben-Dyke).
Melting point: mp >300° (Feuery)
Toxicity data: LD50 orally in rats: 3800-6800 mg/kg; dermally in rabbits: >4000 mg/kg (Ben-Dyke)
Use: Experimentally in horticulture and agriculture. To control suckering of tobacco. In the synthesis of pyridazine.