Mechanistic
aspects of Os(VIII) catalysed oxidation of loop diuretic drug
furosemide
by Ag(III) periodate complex in aqueous alkaline medium
SHWETA J MALODEa,
NAGARAJ P SHETTIb and SHARANAPPA T NANDIBEWOORa,*
aPost-Graduate
Department of Studies in Chemistry, Karnatak University, Dharwad 580 003, India
bDepartment
of Chemistry, KLE Society’s, K. L. E. Institute of Technology, Gokul, Hubli 580
030, India
e-mail:
stnandibewoor@yahoo.com
Abstract.
The kinetics of oxidation of a loop diuretic drug furosemide
(Fur) by diperiodatoargentate(III)
(DPA) has been
investigated in the presence of osmium(VIII) (Os(VIII)) used as homogeneous
catalyst in alkaline
medium at a
constant ionic strength of 0.20mol dm−3 spectrophotometrically
attached with HI-TECH
SFA-12 stopped flow
accessory. The stoichiometry was 1:2 (Fur:DPA). The order of the reaction with
respect
to [DPA] was unity
while the order with respect to [Fur] was less than unity over the
concentration range
studied. The rate
increased with an increase in [OH−]
and decreased with an increase in 
. The order
with respect to
[Os(VIII)] was unity. The oxidation products were identified as 2-(4-carboxy-2-oxo-but-3-
enylamino)-4-chloro-5-sulfamoyl-benzoic
acid and Ag(I). A suitable mechanism was proposed. The reaction
constants involved
in the different steps of the reaction mechanism were calculated. Kinetic
experiments suggest
that [Ag(H2IO6)(H2O)2] is the
reactive silver(III) species and [OsO4(OH)2]2−
is the reactive Os(VIII)
species.
Graphical
Abstract. The
kinetics of oxidation of a loop diuretic drug furosemide by
diperiodatoargentate(III) has
been investigated in presence of osmium(VIII)
used as homogeneous catalyst in
alkaline medium at a constant ionic strength of
0.20 mol dm-3 spectrophotometrically
attached with HI-TECH SFA-12
stopped flow accessory. Active species of DPA and
Os(VIII) were identified.
Keywords. Kinetics; oxidation; diperiodatoargentate(III); furosemide;
Os(VIII) catalysis; mechanism.