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71.
Kanoo P Ghosh AC Cyriac ST Maji TK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(1):237-244
A 3D porous Zn(II) metal-organic framework {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)(H(2)O)]·4H(2)O} (1; H(2)dht=dihydroxyterphthalate, azpy=4,4'-azobipyridine) has been synthesised by employing 2,5-dihydroxyterephthalic acid (H(4)dht), a multidentate ligand and 4,4'-azobipyridine by solvent-diffusion techniques at room temperature. The as-synthesised framework furnishes two different types of channels: one calyx-shaped along the [001] direction and another rectangle-shaped along the [101] direction occupied by guest water molecules. The dehydrated framework, {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)]} (1') provides 52.7% void volume to the total unit-cell volume. The pore surfaces of 1' are decorated with unsaturated Zn(II) sites and pendant hydroxyl groups of H(2)dht linker, thereby resulting in a highly polar pore surface. The dehydrated framework 1' shows highly selective adsorption of CO(2) over other gases, such as N(2), H(2), O(2) and Ar, at 195 K. Photoluminescence studies revealed that compound 1 exhibits green emission (λ(max)≈530 nm) on the basis of the excited-state intramolecular proton-transfer (ESIPT) process of the H(2)dht linker; no emission was observed in dehydrated solid 1'. Such guest-induced on/off emission has been correlated to the structural transformation and concomitant breaking and reforming of the OH···OCO hydrogen-bonding interaction in the H(2)dht linker in 1'/1. 相似文献
72.
Sau SC Santra S Sen TK Mandal SK Koley D 《Chemical communications (Cambridge, England)》2012,48(4):555-557
Palladium complexes bearing abnormal N-heterocyclic carbene were used as catalysts in Suzuki-Miyaura cross coupling of aryl chlorides at 25 °C. The catalyst remained active for 10 successive catalytic runs and can activate 4-chlorotoluene at 25 °C with 0.01 mol% catalyst loading resulting in a TON of 9500 within 6 h. 相似文献
73.
Suresh Chandra Rastogi 《Journal of separation science》1995,18(10):653-658
A gas chromatographic (GC)-mass spectrometric (GC-MS) method has been developed for the routine analysis of 11 fragrance substances in cosmetics: cinnamic alcohol, cinnamic aldehyde, eugenol, hydroxy citronellal, α-amyl cinnamic aldehyde, geraniol, isoeugenol, coumarin, dihydrocoumarin, citronellal and citral. Methods for sample preparation of various types of cosmetic products, prior to GC analysis, have also been developed and proved to be rugged. Detection limits of all of target fragrance substances were approximately 1 ppm. Calibration curves of the target fragrance substances analyzed by GC were found to be linear in the investigated concentration range, 0.005% – 0.50%. The recoveries of the target fragrances from various types of cosmetic products were 80% – 116% and the relative standard deviations of the quantitative analysis of the target fragrance substances were within 5%. 相似文献
74.
Charge-transfer (CT) or electron donor-acceptor (EDA) complex formation between organic donors and acceptors has been extensively
studied by spectrophotometry and other methods. High performance thin layer chromatography (HPTLC), although extensively used
for the identification and quantification of drugs and explosives, has not been used until now to determine the extent of
association and the association constants K
DA of charge transfer or EDA complexes between donor (D) and acceptor (A). This paper describes the use of the HPTLC technique
with scanning densitometry to identify and determine the association constants K
DA of charge-transfer complexes of N,N-diethylaniline (DEA) with different nitro explosives, namely 1,4-dinitrobenzene (DNB),
2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), in chloroform. Advantages of the HPTLC method are highlighted. The
association constants K
DA of the complexes determined using the HPTLC method have been verified and validated spectrophotometrically when the concentrations
of D and A are in their stoichiometric ratio. The thermodynamics of the complex formation reaction were obtained spectrophotometrically
from measurements of the association constants K
DA at five different temperatures ranging from 293 to 313 K, when D and A are in their stoichiometric ratio and also when A≫D. 相似文献
75.
Essential oils derived from six different phenophases, namely early vegetative stage, late vegetative stage, early flowering stage, full flowering stage (FFS), late flowering stage and seed shattering stage of Origanum vulgare L. grown in Kumaon region of Uttarakhand, India were investigated by GC and GC-MS. A total of 38 constituents, representing 97.4-99.7% of the total oil composition, were identified. Major components of oils were thymol (40.9-63.4%), p-cymene, (5.1-25.9%), γ-terpinene (1.4-20.1%), bicyclogermacrene (0.2-6.1%), terpinen-4-ol (3.5-5.9%), α-pinene (1.6-3.1%), 1-octen-3-ol (1.4-2.7%), α-terpinene (1.0-2.2%), carvacrol (<0.1-2.1%), β-caryophyllene (0.5-2.0%) and β-myrcene (1.2-1.9%). Thymol, terpinen-4-ol, 3-octanol, α-pinene, β-pinene, 1,8-cineole, α-cubebene and (E)-β-ocimene were observed to be higher during FFS. The study showed that plant stage had a significant effect on the essential oil content and composition of O. vulgare grown in the hilly tracks of Northern India. 相似文献
76.
Nath NC Sarker S Ahammad AJ Lee JJ 《Physical chemistry chemical physics : PCCP》2012,14(13):4333-4338
Three electrode structures with different spatial arrangements of carbon nanotubes (CNTs) in the mesoporous TiO(2) layer were employed in dye-sensitized solar cells to study the effect of surface states at the interface formed by the incorporation of CNTs. It was found that the decay of open circuit voltage (V(oc)) was significantly minimized by avoiding the direct contact of nanotubes to the conducting substrate by introducing a thin buffer layer of TiO(2) while maintaining the superior electron collection efficiency from the incorporation of nanotubes. 相似文献
77.
Thomas S Paul SK Shandilya S Agarwal A Saxena N Awasthi AK Matta Hb Vir D Mathela CS 《The Analyst》2012,137(15):3571-3582
The present study describes the identification and characterization of two process impurities and major stress degradants in darifenacin hydrobromide using high performance liquid chromatography (HPLC) analysis. Forced degradation studies confirmed that the drug substance was stable under acidic, alkaline, aqueous hydrolysis, thermal and photolytic conditions and susceptible only to oxidative degradation. Impurities were identified using liquid chromatography coupled with ion trap mass spectrometry (LC-MS/MS(n)). Proposed structures were unambiguously confirmed by synthesis followed by characterization using nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR) and elemental analysis (EA). Based on the spectroscopic, spectrometric and elemental analysis data, the unknown impurities were characterized as 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-2-oxo-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-A), 2-[1-(2-benzofuran-5-yl-ethyl)-pyrrolidin-3-yl]-2,2-diphenylacetamide (Imp-B), 2-{1-[2-(2,3-dihydrobenzofuran-5-yl)-ethyl]-1-oxy-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-C) and 2-{1-[2-(7-bromo-2,3-dihydrobenzofuran-5-yl)-ethyl]-pyrrolidin-3-yl}-2,2-diphenylacetamide (Imp-D). Plausible mechanisms for the formation and control of these impurities have also been proposed. The method was validated as per regulatory guidelines to demonstrate specificity, sensitivity, linearity, precision, accuracy and the stability-indicating nature. Regression analysis showed a correlation coefficient value greater than 0.99 for darifenacin hydrobromide and its impurities. The accuracy of the method was established based on the recovery obtained between 86.6 and 106.7% for all impurities. 相似文献
78.
Peleyeju Moses G. Mgedle Nande Viljoen Elvera L. Scurrel Mike S. Ray Sekhar C. 《Research on Chemical Intermediates》2021,47(10):4213-4226
Research on Chemical Intermediates - The application of microwave energy in the synthesis of catalytic materials has been indicated to induce desirable effects that lead to improved activity.... 相似文献
79.
Kalyan Kali Sen Gupta Saroj Chandra Kumar Pratik Kumar Sen Amalendu Banerjee 《Reaction Kinetics and Catalysis Letters》1988,36(2):423-428
The kinetics of oxidation of methanol by bromate ion in hydrochloric acid medium has been investigated. A mechanism consistent with the experimental observations is suggested.
. , .相似文献
80.
Abstract 10-Hydroxycamptothecin is prepared by chemoselective catalytic hydrogenation of the B-ring of camptothecin over PtO2 with sulfur moderators followed by oxidation using iodobenzenediacetate. New moderators (viz. thioanisole, dimethyl sulfide, diphenyl sulfide, 2-mercapto ethanol), which moderate the hydrogenation of the B- ring of camptothecin, are being explored.