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Rohidium carbonyl complexes containing pyridine carboxylic acid ligands : reactivity towards various electrophiles and catalytic activity
Get PDFThe complex [Rh(CO)2Cl]2 reacts with two molar equivalent of pyridine carboxylic acids ligands
Py-2-COOH(a), Py-3-COOH(b) and Py-4-COOH(c) to yield rhodium(I) dicarbonyl chelate
complex [Rh(CO)2(L/)](1a) {L/ = �2-(N,O) coordinated Py-2-COO−(a/)} and non-chelate complexes
[Rh(CO)2ClL//](1b,c) {L// = �1-(N) coordinated Py-3-COOH(b), Py-4-COOH(c)}. The complexes 1 undergo
oxidative addition (OA) reactions with different electrophiles such as CH3I, C2H5I, C6H5CH2Cl and I2 to
give penta coordinated Rh(III) complexes of the types [Rh(CO)(CORn)XL/], {n = 1,2,3; R1 = CH3(2a);
R2 = C2H5(3a); X= I and R3 = CH2C6H5 (4a); X=Cl}, [Rh(CO)I2L/](5a), [Rh(CO)(CORn)ClXL//]
{R1 = CH3(6b,c); R2 = C2H5(7b,c); X= I and R3 = CH2C6H5 (8b,c); X=Cl} and [Rh(CO)ClI2L//](9b,c).
The complexes have been characterized by elemental analysis, IR and 1H NMR spectroscopy. Kinetic
data for the reaction of 1a–b with CH3I indicate a first order reaction. The catalytic activity of 1a–c for
the carbonylation of methanol to acetic acid and its ester is evaluated and a higher turn over number
(TON = 810–1094) is obtained compared with that of the well-known commercial species [Rh(CO)2I2]−
(TON = 653) at mild reaction conditions (temperature 130±5 ◦C, pressure 35±5 bar)
Attenuation of coda waves in the Northeastern Region of India
Get PDFCoda wave attenuation quality factor
Qc is estimated in the northeastern region of India
using 45 local earthquakes recorded by regional
seismic network. The quality factor Qc was estimated
using the single backscattering model modified
by Sato (J Phys Earth 25:27–41, 1977), in
the frequency range 1–18 Hz. The attenuation and
frequency dependence for different paths and the
correlation of the results with geotectonics of the
region are described in this paper. A total of 3,890
Qc measurements covering 187 varying paths are
made for different lapse time window of 20, 30, 40,
50, 60, 70, 80, and 90 s in coda wave. The magnitudes
of the analyzed events range from 1.2 to 3.9
and focal depths range between 7 and 38 km. The
source–receiver distances of the selected events
range between 16 and 270 km. For 30-s duration,
the mean values of the estimated Qc vary from
50 ± 12 (at 1 Hz) to 2,078 ± 211(at 18 Hz) for the Arunachal Himalaya, 49 ± 14 (at 1 Hz) to
2,466 ± 197 (at 18 Hz) for the Indo-Burman, and
45 ± 13 (at 1 Hz) to 2,069 ± 198 (at 18 Hz) for
Shillong group of earthquakes. It is observed
that Qc increases with frequency portraying
an average attenuation relation Qc = 52.315 ±
1.07 f (1.32±0.036) for the region. Moreover, the pattern
of Qc−1 with frequency is analogous to the
estimates obtained in other tectonic areas in the
world, except with the observation that the Qc−1
is much higher at 1Hz for the northeastern region.
The Qc−1 is about 10−1.8 at 1 Hz and decreases to
about 10−3.6 at 18 Hz indicating clear frequency
dependence. Pertaining to the spatial distribution
of Qc values, Mikir Hills and western part
of Shillong Plateau are characterized by lower
attenuation
Expandase-like activity mediated cell-free conversion of ampicillin to cephalexin by Streptomyces sp. DRS I
Get PDFCell-free extracts of Streptomyces sp.
DRS I converted ampicillin to cephalexin, presumably
due to the activity of the enzyme, expandase. The
extract was fractionated and characterized by colorimetric
and chromatographic measurements coupled
with disc-agar diffusion bioassay against an ampicillinresistant,
cephalexin-sensitive E. coli strain. Though
expandase could not be identified, the presence of
a hitherto unreported expandase in Streptomyces sp.
DRS I is suggested
ynthesis, characterisation and thermal studies of ruthenium(II) carbonyl complexes of functionalised tripodal phosphine chalcogen donor ligands, [CH3C(CH2P(X)Ph2)3], where X = Se, S, O
Get PDFdiphenylphosphinomethyl)
ethane trichalcogenide ligands, [CH3C(CH2P(X)Ph2)3], where X= Se(a), S(b) and
O(c) in 1:1 (metal:ligand) molar ratio to afford hexa-coordinated complexes of the type �2-(X,X)-
[Ru(CO)2Cl2P3X3] (1a–c). The complexes 1a–c exhibit two equally intense �(CO) bands in the range
1979–2060cm−1 indicating cis-disposition of the two terminal carbonyl groups. The values of �(CO)
frequencies containing different ligands, in general, follow the order: P3O3 >P3S3 >P3Se3 which may be
explained in terms of ‘Soft–Hard’ (Ru(II)–O) and ‘Soft–Soft’ (Ru(II)–S/Se) interactions. The complexes have
been characterized by elemental analyses, mass, 1H, 31P, 77Se and 13C NMR spectroscopy. The thermal
stability of the complexes has also been studie
Chemical Composition of the Stem Oil of Aristolochia indica L.
Get PDFEssential oil from dry matured stem of Aristolochia indica Linn. family Aristolochiaceae was investigated by GC
and GC/MS. A total of 15 compounds were identified, representing 91.2% of the total oil. The major constituents of
oil were trans-pinocarveol (24.2%), a-pinene (16.4%) and pinocarvone (14.2%)
A Simple and Practical Method for the Oxidation of Thebaine to 14-Hydroxycodeinone by V2O5–H2O2
Get PDFAn efficient, practical and expeditious method has been
developed for the oxidation of thebaine to 14-hydroxycodeinone in
excellent yield by employing 20 mol% of V2O5 in the presence of
30% H2O2 in aqueous medium. The method provides a clean technological
process for the preparation of a key drug intermediate, 14-
hydroxycodeinone
A mild and efficient method for the deformylation of 5-formyl uracils and synthesis of 4'4- methylidenebis (1-phenyl-3 -methyl-5- pyrazolone)
Get PDFTertiary amine effect: synthesis of some novel spirosubstituted pyrido[2,3-d]pyrimidines
Get PDF5-Formyl-6-tertiaryamino uracils 3 prepared from 6-chloro-5-formyl uracil derivative 1 react with barbituric
acids 4 in the presence of base catalyst to afford a novel class of spirosubstituted pyrido[2,3-
d]pyrimidines 5 via 1,6-electro-cyclisation in excellent yields
Towards cleaner degreasing method in industries: ultrasound-assisted aqueous degreasing process in leather making
Get PDFStudies on ultrasound-assisted processes are gaining importance due to its effectiveness and facilitating
green method in processing. Degreasing of skin/hide prior to tanning process is an important unit
operation. Presence of large amounts of natural fat at the interior of skin/hide matrix makes degreasing
process a challenging one. Conventionally, organic solvent and/or detergent based degreasing process are
employed leading to environmental problems. In the present paper, the use of power ultrasound in
aqueous degreasing process has been studied and compared with different degreasing systems.
Glutaraldehyde pre-tanning has also been employed for carrying out the degreasing process at ultrasonic
bath temperature. The results indicate that there is a significant increase in the degreasing efficiency due
to the application of ultrasound. About 2-fold increase in fat removal has been observed due to the use of
ultrasound as compared to control under the given process conditions. Comparing the degreasing
efficiencies of the solvent with aqueous based ultrasonic processes, about 80% of the solvent degreasing
efficiency could be obtained for aqueous degreasing process. This novel ultrasonic process helps in
making aqueous degreasing process a viable option, which is eco-friendly even dispensing with
temperature control measures