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1.
J. Yinon S. Bulusu T. Axenrod H. Yazdekhasti 《Journal of mass spectrometry : JMS》1994,29(11):625-631
Electron impact (EI), chemical ionization and negative-ion chemical ionization (NCI) mass spectra of 1,4-dinitroglycoluril (DINGU), its 15N- and 2H-labeled analogues and the dimethyl-substituted derivatives were recorded. Tandem mass spectrometry with collision induced dissociation was used to study the fragmentation pathways of these compounds. It was found that the main EI fragmentation processes of DINGU are due to the cleavage of C? N bonds and some rearrangement reactions. 相似文献
2.
Rajani K. Samal R. R. Das M. C. Nayak G. V. Suryanarayana G. Panda D. P. Das 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2751-2758
The kinetics of polymerization of acrylonitrile initiated by KHSO5 and catalyzed by Ag(I) have been investigated in an aqueous medium over the temperature range of 35–50°C. The rates of polymerization Rp have been calculated and studied with respect to monomer and initiator. The catalytic activity of various metal ions on the initiator has been determined from a comparison of Rp values. The effects of monomer, catalyst, neutral salts, various amines, and inhibitor (hydroquinone) on the initial rate as well as maximum conversion have been studied. From the kinetics results a suitable reaction scheme has been proposed. 相似文献
3.
A simple liquid chromatographic method was developed for the separation and quantification of voriconazole and its enantiomer
in drug substance. The separation was achieved on Chiral cel-OD (250 mm × 4.6 mm × 10 μm) using mobile phase consisting of
n-hexane and ethanol in the ratio 9:1 (v/v) with a flow rate of 1.0 mL min−1, at 27 °C column temperature and detection at 254 nm with an injection volume of 20 μL. Ethanol was used as diluent. The
method is capable of detecting the (2S, 3R) enantiomer down to 0.0075% and can quantify down to 0.021% with respect to sample concentration. The method is rapid and
the resolution achieved was about 3.0. This method can be employed for the quantification of (2S, 3R) enantiomer in voriconazole drug substance. 相似文献
4.
The intramolecular cycloaddition of the previously described azidoalkene 16 , the related diacetates 7 and 13 , and the monoacetate 8 led diastereoselectivity to the (2R)- and (2S)-configurated hydropyridotriazoles 17 , 9 and 11 , 14 and 15 , and 10 and 12 , respectively (Scheme 1). Thermolysis of 16 gave also the aziridine 18 , its proportion increasing with reaction time. The diastereoselectivity of the cycloaddition- is rationalized on the basis of steric interactions and of H? bonds in the transition state. Photolysis in benzene partially transformed 9 into the aziridine 19 . Treatment of 9 with aqueous AcOH gave 19 and the tetrahydrofuran 20 , with AcOH in benzene 20 and the triacetate 23 , and with aqueous H2SO4 in THF, the primary alcohol 22 (room temperature) or 19 and 22 (0°). Deacetylation of 9 followed by reaction with pyridinium hydrochloride led to the tetrahydrofuran 21 and the chloride 24 (Scheme 2). The diacetate 22 and the triacetate 23 gave the tripl 25 which was deprotected to 26 . Reduction of the keto-aziridine 18 (NaBH4) gave the alcohols 27 and 29 which were acetylated to give 28 and 19 , respectively (Scheme 3). Treatment of the aziridine 28 with AcOH in benzene followed by deacetylation gave 30 and hence 31 . AcOH in benzene transformed the triazoline 15 first into the aziridine 32 and hence into 33 , which was deprotected to give the triol 34 and hence 35 . The 2-(hydroxymethyl)piperidines 26 , 31 , and 35 inhibited Vibrio cholerae sialidase with K1 = 3.8 · 10?2 M, 3.4 · 10?3 M, and 1.5 · 10?4 M, respectively. The conformation of the glycerol side chain of these compounds and of the unbranched piperidines 2–4 deviates from the one of Neu5Ac (and Neu2en5Ac). This finding is rationalized by an H-bond between OH? C(8) and NH? C(6). The conformations and the K1 values of 26 , 31 , and 35 correlate with each other. 相似文献
5.
6.
T. Suryanarayana Murthy D. V. N. Sarma 《Fresenius' Journal of Analytical Chemistry》1958,161(2):114-115
Summary A method for separation of thorium from rare earths in monazite based on the difference of stability of EDTA complexes towards oxine is described. 相似文献
7.
Rajani K. Samal M. C. Nayak G. Panda G. V. Suryanarayana D. P. Das 《Journal of polymer science. Part A, Polymer chemistry》1982,20(1):53-62
Vinyl polymerization of acrylonitrile initiated by the Ce(IV)/thioacetamide redox system has been investigated in aqueous sulfuric acid in the temperature range of 10–20°C. The rate of polymerization (Rp) and the rate of Ce(IV) disappearance (?RCe) were measured. The effect of certain water-soluble organic solvents, added electrolytes, and aromatic and heterocyclic organic nitrogen compounds on the rate of polymerization has been investigated. Depending on the experimental results, we have suggested a suitable reaction scheme for the system which involves the production of initiating radicals from the oxidation of thioacetamide (TAm) by ceric ion and the termination of the polymer chain by metal ions. 相似文献
8.
Summary Let k and l be integers such that 2k l. Let Sk and S
l
lbe two subsets of positive integers with SkQk and Sl Ql, where Qk denotes the set of k-free integers. Further suppose that the characteristic functions of Sk and S
l
l are multiplicative. Let T(n) denote the number of representations of n in the form n=a+b, where a Sk and b S
l
l. In this paper we establish an asymptotic formula for T(n), when n is sufficiently large; and deduce several known asymptotic formulae as particular cases. 相似文献
9.
D. Suryanarayana 《Periodica Mathematica Hungarica》1983,14(1):69-75
LetL(x) denote the number of square-full integers not exceedingx. It is well-known that $$L\left( x \right) \sim \frac{{\zeta \left( {{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} \right)}}{{\zeta \left( 3 \right)}}x^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} + \frac{{\zeta \left( {{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-\nulldelimiterspace} 3}} \right)}}{{\zeta \left( 2 \right)}}x^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}} ,$$ whereζ(s) denotes the Riemann Zeta function, LetΔ(x) denote the error function in the asymptotic formula forL(x). On the assumption of the Riemann hypothesis (R.H.), it is known that $$\Delta x = O\left( {x^{13/81 + 8} } \right)$$ for everyε > 0. In this paper, we prove on the assumption of R.H. that $$\frac{1}{x}\int\limits_x^1 {\left| {\Delta \left( t \right)} \right|dt = O\left( {x^{1/10 + ^8 } } \right)} .$$ In fact, we prove a more general result. We conjecture that $$\Delta x = O\left( {x^{1/10 + ^8 } } \right)$$ under the assumption of the R.H. 相似文献
10.
D. V. Subba Rao P. Radhakrishnanand M. V. Suryanarayana V. Himabindu 《Chromatographia》2007,66(7-8):499-507
An isocratic reversed-phase liquid chromatographic method has been developed for quantitative determination of candesartan
cilexetil, used to treat hypertension, in the bulk drug and in pharmaceutical dosage forms. The method is also applicable
to analysis of related substances. Chromatographic separation was achieved on a 250 mm × 4.6 mm, 5 μm particle, CN column
with a 50:50 (v/v) mixture of phosphate buffer, pH 3.0, and acetonitrile as mobile phase. The flow rate was 1.0 mL min−1 and the detection wavelength was 210 nm. Resolution of candesartan cilexetil and six potential impurities was greater than
2.0 for all pairs of compounds. The drug was subjected to hydrolytic, oxidative, photolytic, and thermal stress and substantial
degradation occurred in alkaline and acidic media and under oxidative and hydrolytic stress conditions. The major product
obtained as a result of basic hydrolysis was different from that produced by acid hydrolysis and aqueous hydrolysis. The stress
samples were assayed against a reference standard and the mass balance was found to be close to 99.6%. The method was validated
for linearity, accuracy, precision, and robustness. 相似文献