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181.
The Conversion of Eperuic Acid into Ethers of the enantio-14, 15-Dinorlabdane Series 5 and 6 are strongly odiferous substances of the ambra-type. Their enantiomers 7 and 8 , hitherto unknown, have been synthesized from eperuic acid (4) and their olfactory properties compared with those of 5 and 6 . 4 was esterified by CH2N2 and dehydrogenated with (C6H5Se)2/H2O2 to the α,β-unsaturated ester 9 (61%). Oxidation by KMnO4 in acetone yielded the ketone 3 (60%). Epoxidation followed by treatment with acid converted 3 into the acetals 7 (61%) and 8 (14%). 7 and 8 differ from 5 and 6 in odor intensity, and 6 and 8 show slightly different odor quality. 相似文献
182.
Vijay Kumar Kawaldeep K. Singh 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(2):131-142
The sum peak method has been applied to electron capture probability changes to the 1086 keV level in the decay of152Eu in the different environments, e.g. ethylenediaminetetraacetic acid (EDTA), bovine serum albumin (BSA) and hydrochloric acid (HCl). An attempt is also made to determine the effect of chemical environment on the directional correlation coefficient of the 1409–122 keV - cascade in152Eu 152Sm decay. A change of G22 is found in the different chemical forms. 相似文献
183.
Patra S Sarkar B Ghumaan S Patil MP Mobin SM Sunoj RB Kaim W Lahiri GK 《Dalton transactions (Cambridge, England : 2003)》2005,(7):1188-1194
The isomeric title complexes were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and L. Crystal structure analyses of the perchlorate hemihydrates, electrochemical and spectroscopic (NMR, UV/VIS, EPR) studies, supported by DFT calculations, reveal distinct differences between the isomeric redox series [1]n+(tetrazine-Nt trans to Cl) and [2]n+(pyrazolyl-Np trans to Cl; n= 0, 1, 2). The latter system with the pi acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidation, lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidised (RuIII) state. According to partially resolved EPR spectra of one-electron reduced neutral compounds and they have the unpaired electron predominantly in the tetrazine ring of L. 相似文献
184.
Devendra Kumar Uday Razdan Alka D. Gupta 《Journal of polymer science. Part A, Polymer chemistry》1993,31(3):797-804
Heat-resistant polymers which are processable into void-free components and suitable for composite applications have been synthesized by thermal/chemical polymerization of four newly developed bisimido-bisphthalonitriles containing silicon, ether, carbonyl, and hexafluoroisopropylidene groups. Thermal polymerization involving addition reactions was performed at 200–275°C for 2–10 h and then post-curing at 310°C for 10 h. Polymers VI, VII, VIII , and IX were obtained. The thermal polymerization was monitored using infrared spectroscopy. Thermal polymerization was also carried out in the presence of an aromatic diamine. A polyhexasocyclane ( V ) was synthesized by condensation polymerization of ether containing bisimido-bisphthalonitrile with 4,4′-diaminodiphenyl ether in solvent phenol. The synthesized polymers were evaluated for thermal stability using dynamic thermogravimetric analysis (TGA). Polymers VII, VIII, IX , and X showed thermal decomposition temperature in the range of 475–500°C in nitrogen and air atmosphere. The char yield of the polymers was in the range of 60–69% in nitrogen at 800°C. This study indicated that synthesized thermosetting polymers from ether and keto containing bisimido-bisphthalo-nitrile are potential candidates for development of graphite composites. © 1993 John Wiley & Sons, Inc. 相似文献
185.
Majumdar G Goswami M Sarma TK Paul A Chattopadhyay A 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):1663-1667
In this letter, we report the synthesis of Au nanoparticles (NPs) and polyaniline (PANI) on the same cation-exchange resin beads and demonstrate their use in catalyzing the oxidation of glucose to gluconic acid by Au NPs and simultaneously in detecting the formation of the acid by the color change of PANI. The synthesis was carried out by exchanging the cations of the resins with HAuCl4 and anilinuium chloride and then reducing the metal ions by NaBH4 to produce Au NPs followed by polymerization of aniline using H2O2. The green emeraldine salt form of PANI thus obtained was treated with NaOH to be converted to blue emeraldine base before use. The deposition of Au NPs was confirmed by a change in color of the bead, visible spectroscopy, X-ray diffraction, and scanning electron microscopic measurements. On the other hand, the presence of PANI was confirmed by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy. The formation of gluconic acid from glucose was confirmed by FTIR spectroscopy. We could detect the presence of glucose of a minimum 1.0 mM concentration in water, using the present method. Our experimental observations demonstrate the possibility of the incorporation of multifunctional components on the surfaces of resins for carrying out a chemical reaction as well as detection of the product. 相似文献
186.
The thermal stability of some boracites, CuB7O13Cl, NiB7O13Br and FeB7O13I, was investigated using thermogravimetry in air up to 1000°, DTA in air to 1200° and evolved gas analysis in vacuum to 1200°C. Only the FeI compound showed weight loss below 1000°C. The endothermic peaks associated with melting were CuCl (1025°C), NiBr (1150°C) and FeI) (965°C). Evolved gas analysis indicated major differences in the decomposition products of the three materials. 相似文献
187.
The role of solvent quality in determining the universal material properties of dilute polymer solutions undergoing steady simple shear flow is examined. A bead-spring chain representation of the polymer molecule is used, and the influence of solvent molecules on polymer conformations is modelled by a narrow Gaussian excluded volume potential that acts pairwise between the beads of the chain. Brownian dynamics simulations data, acquired for chains of finite length, and extrapolated to the limit of infinite chain length, are shown to be model independent. This feature of the narrow Gaussian potential, which leads to results identical to a delta-function repulsive potential, enables the prediction of both universal crossover scaling functions and asymptotic behavior in the excluded volume limit. Universal viscometric functions, obtained by this procedure, are found to exhibit increased shear thinning with increasing solvent quality. In the excluded volume limit, they are found to obey power law scaling with the characteristic shear rate beta, in close agreement with previously obtained renormalization group results. The presence of excluded volume interactions is also shown to lead to a weakening of the alignment of the polymer chain with the flow direction. 相似文献
188.
Sanjib Kumar Saha Ajit Kumar Chaudhuri 《Journal of polymer science. Part A, Polymer chemistry》1987,25(2):519-532
The polymerization of methyl methacrylate was studied in carbon tetrachloride medium with ferric laurate, a metal soap, in combination with n-hexyl amine as the initiator system at 60°C. The rate of polymerization was found to be linear with the monomer concentration and proportional to the square root of both ferric ion and amine concentration. A reaction scheme involving initial complex formation between ferric ion and amine and subsequent reaction of the complex with the solvent molecule to produce free radicals responsible for initiation of polymerization has been postulated to account for the observed results. 相似文献
189.
Amino Acid based cationic surfactants in aqueous solution: physicochemical study and application of supramolecular chirality in ketone reduction 总被引:2,自引:0,他引:2
Roy S Das D Dasgupta A Mitra RN Das PK 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10398-10404
The present study provides a molecular understanding of the origin of the chirality in aqueous micelles and its correlation with the proficiency of stereoselective ketone reduction. The effects of varied headgroup architecture on the surface-active properties as well as on other microstructural parameters were studied and correlated to the structural differences of these naturally occurring amino acid containing surfactants (1-4). Micropolarity sensed by pyrene showed that the micelles prepared using 1-4 are mostly hydrated; particularly large headgroup size surfactant produces more polar environment. A theoretical study was done to quantify the varied spatial dissymmetry for all four surfactants. Asymmetric reduction of prochiral ketones was carried out at the aqueous micellar interface of these chiral amphiphiles by exploiting the supramolecular chirality as evidenced from a circular dichroism study. The enantioselectivity of the reduction process is rationally improved through increase in spatial dissymmetry and steric constraint imposed at the micellar interface by the polar head of surfactants. 相似文献
190.
Benzoxazine-bismaleimide blends: Curing and thermal properties 总被引:4,自引:0,他引:4
A blend of bisphenol A based benzoxazine (Bz-A) and a bismaleimide (2,2-bis[4(4-maleimidophenoxy) phenyl] propane (BMI), was thermally polymerised in varying proportions and their cure and thermal characteristics were investigated. The differential scanning calorimetric analysis, supplemented by rheology confirmed a lowering of the cure temperature of BMI in the blend implying catalysis of the maleimide polymerisation by benzoxazine. FTIR studies provided evidences for the H-bonding between carbonyl group of BMI and -OH group of polybenzoxazine in the cured matrix. The cured matrix manifested a dual phase behaviour in SEM and DMTA with the minor phase constituted by polybenzoxazine dispersed in an interpenetrating polymer network (IPN) of polybenzoxazine and cured BMI. The IPN possessed improved thermal stability over the constituent polybenzoxazine. A benzoxazine monomer possessing allyl functional groups, 2,2′-bis(8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) was reactively blended with the same bismaleimide in varying stoichiometric ratios (Bz-allyl/BMI), where the curing involved mainly Alder-ene reaction between allyl- and maleimides groups and ring-opening polymerisation of benzoxazine. The rheological analysis showed the absence of catalytic polymerisation of BMI in this case. The overall processing temperature was lowered in the blend owing to the co-reaction of the two systems to form a single-phase matrix. The cured resins of both Bz-A/BMI and Bz-allyl/BMI blends exhibited better thermal stability than the respective polybenzoxazines. The Tg of the IPN was significantly improved over that of polybenzoxazine (Bz-A). However, the co-reaction resulted in a marginal decrease in the Tg of the system in comparison to the polybenzoxazine (Bz-allyl). 相似文献