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101.
Dheer Singh Anju Chopra Ravindra Kumar M. I. S. Sastry M. B. Patel B. Basu 《Chromatographia》2014,77(1-2):165-169
EN 14103 is generally used for quantification of ester content in biodiesel free of heptadecanoate ester (C17:0) or methyl nonadecanoate (C19:0), which are employed as internal standards. It was observed that ester content obtained by EN 14103 method did not match with theoretical value of biodiesel, as the method did not take care of response factors of each component to compensate for changes in detector sensitivities. In this study, the whole range of fatty acid (C6–C24:1) methyl esters have been taken into consideration for the calculation of the ester content. Methyl nonadecanoate (C19:0) was used as an internal standard. The response factors of both the saturated and unsaturated methyl esters in the range C6–C24:1 were estimated and found in the range 0.97–1.16. The ester content was calculated after applying the response factors of each methyl ester. The results obtained by this method agreed well with the theoretical value as compared to estimated value using EN14103 method. The results obtained from this method also show good correlation (R 2 = 0.98) with 1H-NMR method. Further, this method does not depend on nature of biodiesel feed stock and is applicable to all methyl biodiesel samples obtained from different raw materials. 相似文献
102.
Importance of cytochromes in cyclization reactions: Quantum chemical study on a model reaction of proguanil to cycloguanil 下载免费PDF全文
Minhajul Arfeen Dhilon S. Patel Sheenu Abbat Nikhil Taxak Prasad V. Bharatam 《Journal of computational chemistry》2014,35(28):2047-2055
Proguanil, an anti‐malarial prodrug, undergoes cytochrome P450 catalyzed biotransformation to the pharmacologically active triazine metabolite (cycloguanil), which inhibits plasmodial dihydrofolate reductase. This cyclization is catalyzed by CYP2C19 and many anti‐malarial lead compounds are being designed and synthesized to exploit this pathway. Quantum chemical calculations were performed using the model species (Cpd I for active species of cytochrome and N4‐isopropyl‐N6‐methylbiguanide for proguanil) to elucidate the mechanism of the cyclization pathway. The overall reaction involves the loss of a water molecule, and is exothermic by approximately 55 kcal/mol, and involves a barrier of approximately 17 kcal/mol. The plausible reaction pathway involves the initial H‐radical abstraction from the isopropyl group by Cpd I, followed by two alternative paths‐ (i) oxygen rebound to provide hydroxyl derivative and (ii) loss of additional H‐radical to yield 1,3,5‐triazatriene, which undergoes cyclization. This study helped in understanding the role of the active species of cytochromes in this important cyclization reaction. © 2014 Wiley Periodicals, Inc. 相似文献
103.
Some new 4-(2,6-diarylpyridin-4-yl)-2H-chromen-2-one derivatives 5a–l have been synthesized by reacting 4-(3-oxo-3-arylprop-1-enyl)-2H-chromen-2-ones 3a–c with appropriate 1-(2-oxo-2-arylethyl)pyridinium bromide salt 4a–d in the presence of ammonium acetate in refluxing glacial acetic acid. The newly synthesized compounds have been characterized by elemental and spectral analysis. 相似文献
104.
Mogon Patel Anthony C. Swain Robert S. Maxwell 《Polymer Degradation and Stability》2006,91(3):548-554
Poly(m-carboranyl-siloxane) elastomers containing a mixture of di-methyl- and methylphenyl-silyl units were synthesised using the ferric chloride catalysed condensation reaction between di-chloro-diorganosilane and bis(di-methylmethoxysilyl)-m-carborane. These elastomeric materials were originally developed to have greater stability to extreme thermal environments and retain tailorable physical and chemical properties relative to comparable non-carborane containing elastomers. Prepared samples were aged either by heating in air at elevated temperatures or by gamma irradiation from a 60Co source. Multinuclear (1H, 13C and 11B) solid and solution state nuclear magnetic resonance (NMR) was used to assess degradation. This included measurements of segmental chain dynamics using a solid-echo pulse sequence reflecting changes in crosslink density and assessing changes to the carborane fragment by 11B and 1H Magic Angle Spinning (MAS) methods. Thermogravimetric measurements were also performed to assess thermal stability. Gamma radiation (to a dose of 1 MGy) was found to induce only a small degree of elastomer hardening as evidenced by a reduction in segmental chain dynamics. The carborane cage however, remained intact at these dose levels. Thermal degradation was observed to lead to oxidative crosslinking, the degree of which is dependent on temperature. At temperatures below 350 °C, only small changes in segmental dynamics were observed commensurate with only minor weight loss at this temperature. At temperatures above 350 °C, the degradation of the elastomer increased dramatically with decreased segmental dynamics and presumed partial oxidation of the carborane cage. The integrity of the m-carborane cage and the segmental dynamics were found to be significantly reduced at temperatures above 580 °C, in line with the known cage rearrangement temperature for icosahedral carboranes. 相似文献
105.
Svetlana N. Mikhaylichenko Saurabh M. Patel Aleksey A. Chesnyuk 《Tetrahedron letters》2009,50(21):2505-2508
We have studied the reaction of methylenedicarbonyl compounds with 4,6-disubstituted 2-hydrazinyl-1,3,5-triazine in order to obtain novel coupled biheterocyclic aromatic systems with potential bioactivity. Reaction conditions were studied and optimized, and a series of 4,6-disubstituted 2-(1H-pyrazolyl)-1,3,5-triazines were obtained with good yield. 相似文献
106.
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108.
Hasmukh S. Patel Sumeet J. Patel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1632-1639
2-Hydroxy benzoic acid hydrazide (1) undergoes facile condensation with aromatic aldehydes to afford the corresponding 2-hydroxy benzoic acid arylidene hydrazides (2a–h) in good yields. Cyclocondensation of compounds 2a–h with thioglycolic acid yields 2-hydroxy-N(4-oxo-2-aryl-thiazolidin-3-yl)-benzamides (3a–h). These 3a–h compounds are for the reacted with benzaldehyde in the presence of sodium ethanolate affords, giving 2-hydroxy-N(5-methylene-4-oxo-2-aryl-thiazolidin-3-yl)-benzamides (4a–h). The structures of these compounds were established on the basis of analytical and spectral data. All the newly synthesized compounds were evaluated for their antibacterial and antifungal activities. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献
109.
Friedel-Crafts polycondensation of β-resorcylic acid (BRA) with p-xylylene dichloride (PXDC) or 4,4′-dichloromethyldiphenyl ether (DDE) in dioxane could be effected without simultaneous decarboxylation of BRA. The similar polycondensation of BRA with PXDC, DDE, or 4,4′-dichloroacetyldiphenyl ether (DADE) in nitrobenzene or in the absence of solvent at 150°C was associated with decarboxylation of BRA. Polymers having structures isomeric with those of the polycondensation product of BRA formed with subsequent in situ decarboxylation were prepared by Friedel-Crafts polycondensation of resorcinol with the above dichlorides. All the polymer samples were characterized, and those with related structures were compared. The ion-exchange properties of the polymer sample prepared from BRA and DDE in dioxane were studied. 相似文献
110.
Polyetheramides (PEAs) are prepared by polycondensation of N,N′-diacetyl-o-tolidide with Bisphenol A, C, or F, phenolphthalein, resorcinol, catechol, hydroquinone, or 1,5- or 2,7-dihydroxynaphthalene or ethylene, butylene, propylene, diethylene, or triethylene glycol. The fusible and soluble oligomers are characterized. An attempt is made to bring out the relationship between various properties of PEAs and their structures. 相似文献