Preparation, Analytical, IR Spectral, and Thermal Studies of Some New Hydrazinium Carboxylates

Hydrazinium salts of 2,4-dichlorophenylacetic acid, phenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, diphenylacetic acid, cinnamic acid, and picolinic and nicotinic acids have been prepared by accomplishing neutralization of aqueous hydrazine hydrate with the respective acids. Formation of these hydrazinium salts has been confirmed by analytical, IR spectral, and thermal studies. IR spectra of the salts register N–N stretching frequencies of ion in the region 963–951？cm？1 and the frequencies of ion in the region 1047–1026？cm？1. Thermal decomposition studies show that the hydrazinium salts undergo melting followed by endothermic decomposition into carbon residue as the endproduct. 1. Introduction Hydrazine is the simplest diamine and forms salt with mineral and carboxylic acids [1–5]. The monoprotonated hydrazine, the hydrazinium cation still retains a basic site and hence capable of coordination with various metal ions. However, many hydrazinium complexes reported in the literature contain hydrazinium ion as a mere charge neutralizing species [6, 7]. The complexes containing coordinated hydrazinium ion are used as very good precursor for the preparation of nanoparticles [8] with nearly uniform particle size. Some of these salts are used as flame-retardants [9, 10] and proton conductors [11]. Preparation and thermal behaviour of some salts from few aliphatic acid [12, 13] and aromatic carboxylic acids [14, 15] have been reported. There is no literature citation about hydrazinium salt of aromatic substituted acetic acids, aromatic unsaturated acids, and heteroacids except hydrazinium salt of pyrazine mono and dicarboxylic acids [16, 17]. It is therefore, considered interesting to prepare hydrazinium salt of aromatic-substituted acetic acids. 2. Experimental All the salts reported have been prepared by the neutralization of the respective acids in aqueous medium with hydrazine hydrate (99–100%) in appropriate molar ratios. 2.1. Preparation 2.1.1. Hydrazinium Salts of 2,4-Dichlorophenylacetate, Phenoxyacetate, 2,4-Dichlorophenoxyacetate, and Diphenylacetate These are prepared by mixing hydrazine hydrate and acids in 2？:？3 molar ratio in 50？mL of distilled water. The resulting turbid solution is heated over water bath to obtain clear solution and concentrated to nearly 20？mL. Then it was allowed to crystallize at room temperature. The crystals are filtered off and washed by using benzene and dried in air. 2.1.2. Hydrazinium Cinnamate Hydrate These are prepared by mixing hydrazine hydrate and diphenylacetic acid or cinnamic acid in 1？:？1 molar ratio in