Preparation and Thermodynamic Characterization of Some Hydroxamic Acids and Their Complexes

Abstract

Benzohydroxamic acid(BHA) and Salicylohydroxamic acid (SHA)were prepared by reacting Benzoic and salicylic acids esters withfree hydroxylamine and recrystallizing them using hot water/acetic acid.characterized by their standard color test with vanadium (V)and iron (III) solution, themelting point resultswere128C , and 169C for BHA and SHA respectively. The IR. spectra show characteristic stretching frequencies of acid functional groups, OH (BHA 3065,SHA 3288.), C=O (BHA 1687.38SHA 1614.64),C-N (BHA 1289, SHA 1353) N-O (BHA 903, SHA 907) cm-1 . H1 NMR spectra shows an(Ar-H's) band at(7.4-7.7) ᵟ (ppm) for BHA and 6.83 –7.832 ᵟ (ppm) for SHA. An NH absorption at 3.1 , 3.3 for BHA and 3.1-3.9 for SHA and an OH absorption at 6.1for BHA and 6.9 for SHA and a Mass spectra of 137for BHA and 153forSHA. Complexes with Zn (II) gavea white complex for both acids. Cu(II) gave a blue complex for BHA and a dark green complex for SHA, Fe(III) gave a reddish brown complex for both acids. Co(II) complexes were pink for both acids. Mn(II) ions gave a white complex with BHA and pale browm complex with SHA. Ni(II) complexes were green for both acids. The complexes were recrystallized with ethanol and characterized by I.R. spectra, SHA showed bands at 1597- 1601 cm-1for(C=O) and 915-925 cm-1for(N-O), BHA showed bands at1598- 1608 cm-1for(C=O) and 918-1035 cm-1for(N-O). Magnetic susceptibility proposes an Octahedral,tetrahedral and square pyramidal geometry for[Fe(SHA2).Cl2] 2H2O, [Co(SHA)2] H2O and a Square pyramidal geometry for [Mn(SHA)Cl.H2O]H2O respectively.TGA results displayed three distinct degradation stages at 100 C , 240 C and 900 C TGA thermogram of all complexes show three characteristics mass loss and residue massas metal oxide. The spectral study reveals that all complexes coordinated to the metal via oxygen atoms (O,O).Stoichiometric measurements......