Abstract:
Four hydroxamic acids were prepared, N- phenyl-N-p- nitrobenzohydroxamic acid
(i) and N-phenyl-n-m-nitrobenzohydroxamic acid (ii) were prepared by the partial
reduction of nitro benzene with zinc dust and ammonium chloride to give β-
phenyl hydroxyl amine which was coupled with p- nitrobenzoyl chloride to give (i)
and with m- nitrobenzoyl chloride to give (ii).
N-p-tolyl-N-benzohydroxamic acid (iii) and N-p-tolyl-N-p-nitrobenzohydroxamic
acid (iv) were prepared by the partial reduction of p- nitro toluene to give N-p-tolyl
hydroxyl amine which was coupled with benzoyl chloride to give compound (iii)
and with p- nitrobenzoyl chloride to give compound (iv).
The hydroxamic acids prepared were identified by their characteristic colored
reaction with vanadium (V) and iron (lll), melting point, i.r. spectra, 1H n.m.r., 13 C
n.m.r., mass spectrometry and G.C. – M.S. spectroscopic techniques.
The extractive properties of hydroxamic acids towards the metals Fe (lll), Cu (ll),
V (V), Mo (Vl), Ni (ll), Co (ll) and Cr (Vl) were examined using appropriate
organic solvent.
The extractability of the hydroxamic acids prepared towards the metals studied
using AAS and uv – vis spectrophotometer for Mo (Vl) and Cr (Vl) was as
follows:
N-phenyl-N-p-nitrobenzohydroxamic acid was found to have a maximum
extraction for Fe (lll) 87.30 % at pH 5.0, Cu (ll) 99.90 % at pH 6.0, Mo (Vl)
69.60% at pH 1.0, Ni (ll) 99.10 % at pH 7.0, Co (ll) 98.83 % at pH 8.0, Cr (Vl)
95.19 % at 3M H2SO4 and V (V) 96.87 % at pH 1.0.
N-phenyl-N-m-nitrobenzohydroxamic acid was found to have a maximum
extraction for Fe (lll) 83.10 % at pH 5.0, Cu (ll) 99.70 % at pH 7.0, Mo (Vl)
v
82.60% at pH 1.0, Ni (ll) 96.10 % at pH 7.0, Co (ll) 98.60 % at pH 8.0, Cr (Vl)
96.24 % at 3M H2SO4 and V (V) 93.88 % at pH 1.0.
N-p- tolyl -N-benzohydroxamic acid was found to have a maximum extraction for
Fe (lll) 75.10 % at pH 5.0, Cu (ll) 99.81% at pH 5.0, Mo (Vl) 95.50 % at pH 1.0,
Ni (ll) 59.45 % at pH 7.0, Co (ll) 99.40 % at pH 10.0, Cr (Vl) 91.10 % at 3M
H2SO4 and V (V) 91.63 % at pH 2.0.
N-p- tolyl -N-p-nitrobenzohydroxamic acid was found to have a maximum
extraction for Fe (lll) 67.40 % at pH 5.0, Cu (ll) 99.94% at pH 6.0, Mo (Vl)
94.40% at pH 1.0, Ni (ll) 29.60 % at pH 7.0, Co (ll) 97.35 % at pH 10.0, Cr (Vl)
59.70 % at 3M H2SO4 and V (V) 96.15 % at pH 1.0.
The four hydroxamic acids were found to extract efficiently metals like Mo (Vl),
Cr (Vl) and V (V) in acidic pH values, Ni (ll) in neutral pH values, Fe (lll), Cu (ll),
in pH near to neutral and Co (ll) at alkali pH values.
