3587-64-2Relevant academic research and scientific papers
HYDROGEN-BONDING IN NON-CYCLIC VICINAL DIOLS AND THEIR MONO-METHYL ETHERS: AN FTIR STUDY
Singelenberg, F.A.J,Maas, J. H. Van Der
, p. 111 - 122 (1991)
Thirteen vicinal diols and their mono-alkyl ethers, dissolved in CCl4 and CS2, have been studied in the fundamental OH-stretching region.These systems are predominantly present in the intramolecular H-bonded form.The frequencies of the OH donor appears to be mainly determined by two effects: the character of the donor and its molecular surroundings.The frequency decreases on going over from primary to secondary and tertiary OH groups.The difference in the molecular surroundings is related to shielding of the H bond from the solvent and is expressed in a decrease ofthe frequency.For the diols evidence is found for a double, cyclic intramolecular H bond next to a single H bond in which one OH acts as a donor and another one as an acceptor.The proton of an acceptor OH is present in a preferential position and the corresponding OH frequency is increased with respect to the mono-hydroxy analogue.
Zeolite 4A supported CdS/g-C3N4 type-II heterojunction: A novel visible-light-active ternary nanocomposite for potential photocatalytic degradation of cefoperazone
AttariKhasraghi, Naime,Behnajady, Mohammad A.,Mehrizad, Ali,Modirshahla, Nasser,Zare, Karim
, (2021/09/15)
The CdS/g-C3N4 heterojunction photocatalyst supported on 4A zeolite was successfully synthesized using a simple chemical precipitation method. The physicochemical characteristics of the as-prepared ternary composite were assessed using X-Ray diffraction (XRD), field emission- scanning electron microscopy (FE-SEM), energy dispersive X-Ray (EDX), transmission electron microscopy (TEM), N2 adsorption–desorption, differential reflectance spectroscopy (UV–Vis-DRS), and photoluminescence (PL) techniques. The results confirmed the successful synthesis of the CdS/g-C3N4/4AZ nanocomposite and introduction of the CdS and g-C3N4 on the substrate of 4A zeolite. Cefoperazone (CFP) antibiotic was tested as the model pollutant to assess the photocatalytic performance of the synthesized nanocomposite under visible light irradiation. The response surface methodology (RSM) and artificial neural network (ANN) showed desirable reasonability for the prediction of the CFP degradation efficiency. More than 93% of CFP with a concentration of 17 mg L-1 degraded in the presence of the 0.4 g L-1 of the catalyst at pH of 9 after 80 min treatment time (RSM-based optimization results). The pH of the solution, irradiation time, catalyst dosage, and the initial concentration of the CFP affected degradation efficiency with a percentage impact of 37, 29, 19, and 15 %, respectively (ANN-based modeling results). The addition of 1 mM of isopropanol, benzoquinone, and sodium oxalate reduced the CFP degradation efficiency from 93.23% to 85.18, 41.16, and 32.47%, respectively, proving the decisive role of the °O2– and h+ in the photodegradation process. The kinetic studies indicated the following of the process from the Langmuir-Hinshelwood's pseudo-first-order model (kapp = 3.71 × 10-2 min?1). The structure of the identified by-products using GC-MS analysis confirmed that CFP mainly decomposed through the cleavage of C-S, C-N, and N-N bonds. Moreover, the formation of the aliphatic compounds and carboxylic acids as by-products confirmed nearly complete mineralization of the CFP to non-toxic products.
Influence of Hydrogen Bond Donating Sites in UiO-66 Metal-Organic Framework for Highly Regioselective Methanolysis of Epoxides
Anbu, Nagaraj,Biswas, Shyam,Das, Aniruddha,Dhakshinamoorthy, Amarajothi,Sk, Mostakim
, (2020/02/18)
A Zr(IV)-based UiO-66 metal-organic framework (MOF) (named 1) was synthesized by employing 1-(aminomethyl)naphthalene-2-ol appended terephthalate linker and Zr(IV) salt via solvothermal method and subsequently characterized. Furthermore, the potential efficiency of activated (named 1′) form of as-synthesized MOF was investigated as an organocatalyst for the ring-opening of epoxide by methanol. The catalytic performance of 1 and 1′ was studied in the methanolysis of styrene oxide as a model substrate and the activity of 1′ was also examined with various alcohols. Under the optimized reaction conditions, the catalytic performance of 1′ reached 96 % conversion of styrene oxide to its corresponding product with 98 % regioselectivity. The reusability and stability of the catalyst were proved by recycling up to four runs in the methanolysis of styrene oxide. The Lewis acidity originating from metal nodes and hydrogen bond donating (HBD) sites in the linker is distributed homogeneously throughout the framework, thus playing crucial role in the activation of epoxide with easy accessibility.
Epoxide ring opening with alcohols using heterogeneous Lewis acid catalysts: Regioselectivity and mechanism
Deshpande, Nitish,Parulkar, Aamena,Joshi, Rutuja,Diep, Brian,Kulkarni, Ambarish,Brunelli, Nicholas A.
, p. 46 - 54 (2019/01/04)
Lewis acidic catalytic materials are investigated for the regioselective ring opening of epoxides with alcohols. For ring opening epichlorohydrin with methanol, the catalytic activity shows a strong dependence on the type of support and Lewis acidic species used. While Sn-SBA-15 is catalytically active, significantly higher catalytic activity can be achieved with hydrothermally synthesized zeolites of which Sn-Beta is 6 and 7 times more active than Zr-Beta or Hf-Beta, respectively. Sn-Beta is determined to be more active and more regioselective for epoxide ring opening of epichlorohydrin with methanol than Al-Beta. For Sn-Beta, the activation energy for the reaction between epichlorohydrin and methanol is determined to be 53 ± 7 kJ mol?1. For epichlorohydrin, the activation energy barrier and experimentally observed regioselectivity are found using DFT to be consistent with a concerted reaction mechanism involving activation of the epoxide on an alcohol adsorbed on the catalytic site and nucleophilic attack by a second alcohol. The epoxide is shown to impact the regioselectivity and the mechanism since isobutylene oxide is selectively ring opened by methanol to form the terminal alcohol. DFT calculations indicate the mechanism for isobutylene ring opening involves epoxide activation and ring opening on an alcohol adsorbed onto the catalytic site. Finally, catalyst reuse testing indicates that Sn-Beta can be used for multiple reactions with no decrease in activity and limited to no leaching of the tin site, demonstrating Sn-Beta is a promising catalytic material for epoxide ring opening reactions with alcohols.
Influence of functionalization of terephthalate linker on the catalytic activity of UiO-66 for epoxide ring opening
Blandez, Juan F.,Santiago-Portillo, Andrea,Navalón, Sergio,Giménez-Marqués, Mónica,álvaro, Mercedes,Horcajada, Patricia,García, Hermenegildo
, p. 332 - 339 (2016/12/09)
A series of five isostructural zirconium terephthalate UiO-66 metal organic frameworks bearing different functional groups on the terephthalate linker (UiO-66-X; X = H, NH2, NO2, Br, Cl,) have been successfully prepared and characterized. UiO-66-X materials were evaluated as heterogeneous catalysts for the epoxide ring opening of styrene oxide by methanol, observing an increase in the initial reaction rate from UiO-66-H to UiO-66-Br, over one order of magnitude. The reactivity order, however, does not follow a linear relationship between the Hammett constant value of the substituent and the initial reaction rate. UiO-66-Br exhibits a wide scope, its activity depending on the structure of epoxide and nucleophile. The absence of Zr leaching to the solution together with the preservation of the UiO-66-X crystallinity confirms the stability of the framework under the reaction conditions. Nevertheless, UiO-66 undergoes a progressive deactivation upon reuse that was attributed to a strong adsorption of the reaction product.
Enhancement of CO2 Adsorption and Catalytic Properties by Fe-Doping of [Ga2(OH)2(L)] (H4L = Biphenyl-3,3′,5,5′-tetracarboxylic Acid), MFM-300(Ga2)
Krap, Cristina P.,Newby, Ruth,Dhakshinamoorthy, Amarajothi,García, Hermenegildo,Cebula, Izabela,Easun, Timothy L.,Savage, Mathew,Eyley, Jennifer E.,Gao, Shan,Blake, Alexander J.,Lewis, William,Beton, Peter H.,Warren, Mark R.,Allan, David R.,Frogley, Mark D.,Tang, Chiu C.,Cinque, Gianfelice,Yang, Sihai,Schr?der, Martin
, p. 1076 - 1088 (2016/02/09)
Metal-organic frameworks (MOFs) are usually synthesized using a single type of metal ion, and MOFs containing mixtures of different metal ions are of great interest and represent a methodology to enhance and tune materials properties. We report the synthesis of [Ga2(OH)2(L)] (H4L = biphenyl-3,3′,5,5′-tetracarboxylic acid), designated as MFM-300(Ga2), (MFM = Manchester Framework Material replacing NOTT designation), by solvothermal reaction of Ga(NO3)3 and H4L in a mixture of DMF, THF, and water containing HCl for 3 days. MFM-300(Ga2) crystallizes in the tetragonal space group I4122, a = b = 15.0174(7) ? and c = 11.9111(11) ? and is isostructural with the Al(III) analogue MFM-300(Al2) with pores decorated with -OH groups bridging Ga(III) centers. The isostructural Fe-doped material [Ga1.87Fe0.13(OH)2(L)], MFM-300(Ga1.87Fe0.13), can be prepared under similar conditions to MFM-300(Ga2) via reaction of a homogeneous mixture of Fe(NO3)3 and Ga(NO3)3 with biphenyl-3,3′,5,5′-tetracarboxylic acid. An Fe(III)-based material [Fe3O1.5(OH)(HL)(L)0.5(H2O)3.5], MFM-310(Fe), was synthesized with Fe(NO3)3 and the same ligand via hydrothermal methods. [MFM-310(Fe)] crystallizes in the orthorhombic space group Pmn21 with a = 10.560(4) ?, b = 19.451(8) ?, and c = 11.773(5) ? and incorporates μ3-oxo-centered trinuclear iron cluster nodes connected by ligands to give a 3D nonporous framework that has a different structure to the MFM-300 series. Thus, Fe-doping can be used to monitor the effects of the heteroatom center within a parent Ga(III) framework without the requirement of synthesizing the isostructural Fe(III) analogue [Fe2(OH)2(L)], MFM-300(Fe2), which we have thus far been unable to prepare. Fe-doping of MFM-300(Ga2) affords positive effects on gas adsorption capacities, particularly for CO2 adsorption, whereby MFM-300(Ga1.87Fe0.13) shows a 49% enhancement of CO2 adsorption capacity in comparison to the homometallic parent material. We thus report herein the highest CO2 uptake (2.86 mmol g-1 at 273 K at 1 bar) for a Ga-based MOF. The single-crystal X-ray structures of MFM-300(Ga2)-solv, MFM-300(Ga2), MFM-300(Ga2)·2.35CO2, MFM-300(Ga1.87Fe0.13)-solv, MFM-300(Ga1.87Fe0.13), and MFM-300(Ga1.87Fe0.13)·2.0CO2 have been determined. Most notably, in situ single-crystal diffraction studies of gas-loaded materials have revealed that Fe-doping has a significant impact on the molecular details for CO2 binding in the pore, with the bridging M-OH hydroxyl groups being preferred binding sites for CO2 within these framework materials. In situ synchrotron IR spectroscopic measurements on CO2 binding with respect to the -OH groups in the pore are consistent with the above structural analyses. In addition, we found that, compared to MFM-300(Ga2), Fe-doped MFM-300(Ga1.87Fe0.13) shows improved catalytic properties for the ring-opening reaction of styrene oxide, but similar activity for the room-temperature acetylation of benzaldehyde by methanol. The role of Fe-doping in these systems is discussed as a mechanism for enhancing porosity and the structural integrity of the parent material.
MIL-101-SO3H: A highly efficient Bronsted acid catalyst for heterogeneous alcoholysis of epoxides under ambient conditions
Zhou, Yu-Xiao,Chen, Yu-Zhen,Hu, Yingli,Huang, Gang,Yu, Shu-Hong,Jiang, Hai-Long
, p. 14976 - 14980 (2015/01/09)
For the first time, a ～100% sulfonic acid functionalized metal-organic framework (MOF), MIL-101-SO3H, with giant pores has been prepared by a hydrothermal process followed by a facile postsynthetic HCl treatment strategy. The replete readily accessible Lewis acidic and especially Bronsted acidic sites distributed throughout the framework as well as high stability endow the resultant MOF exceptionally high efficiency and recyclability, which surpass all other MOF-based catalysts, for the ring opening of epoxides with alcohols (especially, methanol) as nucleophiles under ambient conditions.
ANTIVIRAL ETHERS OF ASPARTATE PROTEASE SUBSTRATE ISOSTERES
-
, (2008/06/13)
Antiretroviral compounds (which are effective, for example, against HIV) of the formula I STR1 in which R 1 is an acyl radical lower-alkoxyl-lower-alkanoyl whose lower alkoxy radical is unsubstituted or is substituted by halogen, phenyl, lower alkoxy or a heterocyclic radical selected from piperidinyl, pyrrolidinyl, tetrahydropyranyl, tetrahydrofuranyl, thiazolidinyl, thiazolyl, indolyl or 4H-1-benzopyranyl which is unsubstituted or substituted by oxo, hydroxyl, amine, lower alkyl, lower-alkoxycarbonyl and/or phenyl-lower-alkoxycarbonyl; lower alkanoyl which is unsubstituted or is substituted by one of the said unsubstituted or substituted heterocyclic radicals; arylcarbonyl or heterocyclylcarbonyl which are substituted by heterocyclyl or heterocyclyl-lower-alkyl; phenyl-lower-alkanoyl which is substituted by hydroxyl and lower alkyl; or arylsulfonyl;or the residue of an amino acid which is defined in accordance with the description (and which may be acylated on the amino nitrogen by one of the abovementioned acyl radicals);R 2 and R 3 are in each case cyclohexyl, cyclohexenyl, phenyl, naphthyl or tetrahydronaphthyl which are unsubstituted or substituted by lower alkyl, phenyl, cyanophenyl, phenyl-lower-alkyl, halogen, halo-lower-alkyl, cyano, hydroxyl, lower alkoxy, phenyl-lower-alkoxyl, pyridyl-lower-alkoxy, lower-alkoxy-lower-alkoxy, lower-alkoxycarbonyl-lower-alkoxy, carboxyl-lower-alkoxy, hydroxyl-lower-alkoxy, carbamoyl-lower-alkoxy, cyano-lower-alkoxy, and phenyl-lower-alkanesulfonyl which is unsubstituted or substituted by halogen;R 4 is lower alkyl, cyclohexyl or phenyl; and R 5 is lower alkyl; and n is 1 or 2, or salts thereof, are novel.
EFFICIENT AND/OR SELECTIVE METHYLATION BY DIAZOMETHANE OF ALCOHOLS, HALO ALCOHOLS, GLYCOLS, AMINO ALCOHOLS AND MERCAPTO ALCOHOLS WITH THE USE OF A PROTON-EXCHANGED X-TYPE ZEOLITE AS AN ACID-BASE BIFUNCTIONAL CATALYST
Takeuchi, Hiroshi,Kishioka, Hiroaki,Kitajima, Kunio
, p. 121 - 126 (2007/10/02)
Reactions of diazomethane with butanol, allyl alcohol and β- and γ-halo alcohols led to efficient methylation (giving the corresponding methyl ethers) with the use of a proton-excahnged X-type zeolite compared with H2SO4.The reactions with propylene and isobutylene glycols using the zeolite provided regioselective methylation of the primary OH rather than the secondary or tertiary OH, whereas regioselectivity was not observed in the reactions using H2SO4.The reactions with 2-aminoethanol and 2-mercaptoethanol showed high chemoselective S-methylation and N-monomethylation, respectively, in the presence of the zeolite instead of H2SO4.The mechanism for the reactions is proposed to involve acid-base bifunctional catalysis of the zeolite in which the acidic site reacts with diazomethane to form its conjugate acid, and the nucleophilicity of OH and SH groups is enhanced by the interaction of the basic site with the proton of the groups.
Monomeric Volatile Alkoxides of Chromium and Bismuth
Herrmann, Wolfgang A.,Huber, Norbert W.,Anwander, Reiner,Priermeier, Thomas
, p. 1127 - 1130 (2007/10/02)
The β-methoxy alcohol HOCMe2CH2OMe (1) yields monomeric (mononuclear), highly volatile and soluble complexes M(OCMe2CH2OMe)3 3a, b of chromium(III) and bismuth(III), respectively, upon treatment with the amide precursors Cr3 (2a) and Bi3 (2b).A single-crystal X-ray diffraction analysis of 3a was performed because of the novelty of this particular compound being the first thermostable monomeric alkoxide of trivalent chromium. 3a exhibits an octahedral structure with six oxygen atoms surrounding the metal atom.Three chelating O,O'ligands coordinate to Cr(III) in a mer configuration.Key words: Chromium / Bismuth / Alkoxides
