79-20-9Relevant articles and documents
Insights into the Pyridine-Modified MOR Zeolite Catalysts for DME Carbonylation
Cao, Kaipeng,Fan, Dong,Li, Lingyun,Fan, Benhan,Wang, Linying,Zhu, Dali,Wang, Quanyi,Tian, Peng,Liu, Zhongmin
, p. 3372 - 3380 (2020)
Pyridine-modified mordenite (MOR) zeolite catalysts have attracted great attention in recent years due to their unique shape selectivity within eight-membered ring (8-MR) side pockets for dimethyl ether (DME) carbonylation to methyl acetate (MA) and syngas conversion to ethylene. Herein, aimed at elucidating pyridine modification-carbonylation activity relationships and developing high-performance catalysts, we investigated the adsorption/desorption behaviors of pyridine on MOR zeolites with varying Si/Al ratios and their impact on DME carbonylation. Instead of the previously proposed selective adsorption of pyridine in 12-MR channels, pyridine is revealed to penetrate into 8-MR side pockets of MOR zeolites and interact with acidic hydroxyls therein. Upon heating, pyridine in pockets desorbs preferentially, likely arising from the lower stability of pyridine adspecies in constrained spaces. This well explains the observed increment of carbonylation activity following the increase of pretreatment temperature. Unprecedentedly, high MA yield (7.2 mmol/(h g)) has been achieved on pyridine-modified MOR (Si/Al = 13.8) under controlled pyridine desorption conditions, resulting from the joint contributions of better diffusion properties and larger amounts of active acid sites. Moreover, the catalytic activity of Br?nsted acid sites within 8-MR pockets is demonstrated to be inhomogeneous, closely associated with their locations.
Chemiluminescence upon isomerization of dimethyldioxirane in the gas phase and on a sorbent surface
Kazakov,Voloshin,Kabal'Nova,Shereshovets,Kazakov
, p. 2452 - 2453 (1996)
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of Chemiluminescence. 1997 Plenum Publishing Corporation.
Poller,Retout
, p. C7 (1979)
Purification of EMIMOAc used in the acetylation of lignocellulose
Shi, Jin-Zhi,Stein, Juergen,Kabasci, Stephan,Pang, Hao
, p. 197 - 202 (2013)
Up to now, several methods of purifying ionic liquids (ILs), such as the extraction with supercritical carbon dioxide, crystallization, column chromatography, and so forth were reported. The IL that was used in the acetylation of lignocellulose with the help of acetic anhydride contains an elevated amount of acetic acid. In this paper our investigations on the separation of acetic acid from synthetic mixtures with 1-ethyl-3- methylimidazolium acetate (EMIMOAc) are described. The separation was performed by evaporation, extraction, and esterification. While impurities like ethyl acetate, n-propyl acetate, isopropyl acetate, and tetrahydrofuran (THF) can easily be evaporated from EMIMOAc, it is difficult to remove acetic acid from EMIMOAC or EMIMCl by evaporation below certain concentration levels. In extraction tests acetic acid could be separated from EMIMOAc to some degree, especially with extractants immiscible with EMIMOAc having a high value of ET(30) and a dielectric constant near that of acetic acid. The most successful removal of acetic acid was found to be an esterification of acetic acid at a large excess of alcohol, a long reaction time, and an intensive contact of the educts in the liquid phase at elevated temperature and pressure with subsequent evaporation of the produced acetic acid ester.
Novel synthesis and catalytic performance of hierarchical MOR
Lu, Jiaxin,Wang, Yaquan,Sun, Chao,Zhao, Taotao,Zhao, Jingjing,Wang, Ziyang,Liu, Wenrong,Wu, Shuhui,Shi, Mingxue,Bu, Lingzhen
, p. 8629 - 8638 (2021)
A novel route was developed to synthesize hierarchical MOR through introduction of BEA/MOR zeolite embryos as the structural growth inducer (SGI) in the presence of hexadecyltrimethylammonium (CTA+). The morphologies, physicochemical properties and possible formation mechanism of the hierarchical MOR were studied systematically. In the process of crystallization, CTA+ might act as a crystal growth inhibitor for the formation of BEA zeolite; therefore, the MOR embryos have the chance to induce the growth of MOR. Besides, CTA+ ions interact with the primary crystals formed and result in the formation of mesopores. Through changing the addition of CTAB and SGI, the crystal sizes, the mesopore volume and the acidity of the hierarchical MOR could be adjusted. Compared with commercial MOR, the catalytic stability of the hierarchical MOR is much higher in the carbonylation of dimethyl ether.
Stability enhancement of H-mordenite in dimethyl ether carbonylation to methyl acetate by pre-adsorption of pyridine
Liu, Junlong,Xue, Huifu,Huang, Xiumin,Wu, Pei-Hao,Huang, Shing-Jong,Liu, Shang-Bin,Shen, Wenjie
, p. 729 - 738 (2010)
The carbonylation of dimethyl ether to methyl acetate over H-mordenite (HMOR) and pyridine-modified HMOR was compared. The catalytic stability of HMOR was improved significantly by pyridine pre-adsorption, and a yield of methyl acetate ~30 was still obtained after 48 h on stream at 473 K. In situ infrared spectroscopy and ammonia temperature-programmed desorption revealed that pyridine preferentially occupied the acidic sites in 12-membered ring pores but not the acidic sites in 8-membered ring pores. 129Xe NMR studies suggested that the channels of HMOR were blocked by coke in the reaction but those in the pyridine-modified HMOR were not. The acidic sites in the 12-membered ring pores were responsible for the deactivation of HMOR, and the reaction can be directed to occur mainly on the acidic sties in the 8-membered ring pores by the selective adsorption of pyridine in the 12-membered ring pores.
Specificity of sites within eight-membered ring zeolite channels for carbonylation of methyls to acetyls
Bhan, Aditya,Allian, Ayman D.,Sunley, Glenn J.,Law, David J.,Iglesia, Enrique
, p. 4919 - 4924 (2007)
The acid-catalyzed formation of carbon-carbon bonds from C1 precursors via CO insertion into chemisorbed methyl groups occurs selectively within eight-membered ring (8-MR) zeolite channels. This elementary step controls catalytic carbonylation rates of dimethyl ether (DME) to methyl acetate. The number of O-H groups within 8-MR channels was measured by rigorous deconvolution of the infrared bands for O-H groups in cation-exchanged and acid forms of mordenite (M,H-MOR) and ferrierite (H-FER) after adsorption of basic probe molecules of varying size. DME carbonylation rates are proportional to the number of O-H groups within 8-MR channels. Na+ cations selectively replaced protons within 8-MR channels and led to a disproportionate decrease in carbonylation turnover rates (per total H+). These conclusions are consistent with the low or undetectable rates of carbonylation on zeolites without 8-MR channels (H-BEA, H-FAU, H-MFI). Such specificity of methyl reactivity upon confinement within small channels appears to be unprecedented in catalysis by microporous solids, which typically select reactions by size exclusion of bulkier transition states.
Mechanism of acetic acid esterification over sulfonic acid-functionalized mesoporous silica
Miao, Shaojun,Shanks, Brent H.
, p. 136 - 143 (2011)
The kinetics of acetic acid esterification with methanol using a propylsulfonic acid-functionalized SBA-15 catalyst were investigated. To determine whether a different mechanism was applicable for heterogeneous or homogeneous catalyzed esterification, propane sulfonic acid was also examined as this homogeneous acid has the same structure as the functional groups tethered onto SBA-15. In isothermal experiments at 323 K, the apparent reaction orders using the heterogeneous catalyst were determined to be 0.72 for methanol and 0.87 for acetic acid. Reactant adsorption studies showed that pre-adsorption of acetic acid hindered the reaction rate, while pre-adsorption of methanol or acetic acid with methanol increased the reaction rate, indicating that acetic acid adsorbs more strongly than methanol over the heterogeneous acid catalyst. The experimental results demonstrated that acetic acid esterification with methanol followed a dual-site Langmuir-Hinshelwood type reaction mechanism, which required both the adsorption of acetic acid and methanol over propylsulfonic acid-functionalized SBA-15. In contrast, esterification reaction with the homogeneous catalyst followed an Eley-Rideal mechanism. The kinetic data were successfully fit with a model in which the surface reaction was the rate-limiting step.
DME carbonylation over a HSUZ-4 zeolite
Xiong, Zhiping,Zhan, Ensheng,Li, Mingrun,Shen, Wenjie
, p. 3401 - 3404 (2020)
Zeolite-catalyzed carbonylation of dimethyl ether to methyl acetate represents a new route to synthesize acetyls. A rod-shaped HSUZ-4 zeolite, with intersecting 10-member ring and 8-member ring channels, showed exceptionally high activity and durability, as compared to the HZSM-35 sharing a similar pore structure. The abundant openings of 8-member ring pores, as determined by the shape of HSUZ-4, facilitated the diffusion of the reactive molecules.
Chemiluminescence in the reaction of the RuII trisbipyridyl complex with dimethyldioxirane
Kazakov,Voloshin,Kabal'nova,Shereshovets,Kazakov
, p. 1089 - 1093 (1997)
The reaction of dimethyldioxirane (1) with the RuII trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the rate of its decay increase proportionally with the concentration of RuII. The bimolecular rate constant (k2) of the reaction of 1 with RuII was determined. The activation parameters (Ea and logA) for this reaction were calculated from the temperature dependence of k2. The excitation yield of RuII* (η*Ru) was estimated. The quenching of RuII* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined. It was suggested that the catalysis of the decomposition of 1 and the excitation of RuII occur via a mechanism of chemically initiated electron exchange.
Identifying the Active Silver Species in Carbonylation of Dimethyl Ether over Ag?HMOR
Li, Shiyue,Cai, Kai,Li, Ying,Liu, Shuaipeng,Yu, Man,Wang, Yue,Ma, Xinbin,Huang, Shouying
, p. 3290 - 3297 (2020)
As one of the key steps in ethanol production from syngas, dimethyl ether (DME) carbonylation to methyl acetate (MA) catalyzed by zeolite has drawn much attention. H-mordenite (HMOR) modified with metal has been continuously developed for improving catalytic performance. Here, we investigated the role of Ag species through three series of Ag?HMOR catalysts prepared through altering Ag loading, varying reduction temperature and additional ion exchange. TEM, XPS, CO FTIR and UV-Vis spectroscopy were employed to identify the nature and the amount of Ag species in xAg?HM with different Ag loading. Taken together with catalytic performance evaluation, 5Ag?HM with the moderate size of Ag0 species (Agnδ+ and Agm clusters) was proved to have greatest promotion effect on DME carbonylation. This was also evidenced by further improved MA formation rate over catalysts via elevating reduction temperature or via additional NH4Cl ion exchange, which contained more Ag0 and fewer Ag+ species respectively. These provide insight into metal-modified HMOR, inspiring design and fabrication of zeolite catalysts with multi-active sites.
An Enzyme Model Which Mimics Chymotrypsin and N-Terminal Hydrolases
Fuentes De Arriba, ángel L.,García, Miguel Martínez,Garrido-González, José J.,Iglesias Aparicio, Ma Mercedes,Morán, Joaquín R.,Sanz, Francisca,Simón, Luis
, p. 11162 - 11170 (2020)
Enzymes are the most efficient and specific catalysts to date. Although they have been thoroughly studied for years, building a true enzyme mimic remains a challenging and necessary task. Here, we show how a three-dimensional geometry analysis of the key catalytic residues in natural hydrolases has been exploited to design and synthesize small-molecule artificial enzymes which mimic the active centers of chymotrypsin and N-terminal hydrolases. The optimized prototype catalyzes the methanolysis of the acyl enzyme mimic with a half-life of only 3.7 min at 20 °C, and it is also able to perform the transesterification of vinyl acetate at room temperature. DFT studies and X-ray diffraction analysis of the catalyst bound to a transition state analogue proves the similarity with the geometry of natural hydrolases.
Octyl Co-grafted PrSO3H/SBA-15: Tunable Hydrophobic Solid Acid Catalysts for Acetic Acid Esterification
Manayil, Jinesh C.,dos Santos, Vannia C.,Jentoft, Friederike C.,Granollers Mesa, Marta,Lee, Adam F.,Wilson, Karen
, p. 2231 - 2238 (2017)
Propylsulfonic acid (PrSO3H) derivatised solid acid catalysts have been prepared by post-modification of mesoporous SBA-15 silica with mercaptopropyltrimethoxysilane (MPTMS), and the impact of co-derivatisation with octyltrimethoxysilane (OTMS) groups to impart hydrophobicity to the catalyst was investigated. Turnover frequencies (TOFs) for acetic acid esterification with methanol increase with PrSO3H surface coverage across both families, suggesting a cooperative effect between adjacent acid sites at high acid site densities. Esterification activity is further promoted upon co-functionalisation with hydrophobic octyl chains, with inverse gas chromatography (IGC) measurements indicating that the increased activity correlates with decreased surface polarity or increased hydrophobicity.
Schowen,Behn
, p. 5839 (1968)
Sulfonic-acid-functionalized porous benzene phenol polymer and carbon for catalytic esterification of methanol with acetic acid
Tian, Xiaoning,Zhang, Li Li,Bai, Peng,Zhao
, p. 53 - 59 (2011)
Porous benzene phenol polymer and carbon were synthesized in the presence of Pluronic P123 as template. Sulfonation of the porous structures yielded solids with sulfonic acid groups. The compositions of the solid acids were characterized using elemental analysis and thermogravimetric analysis methods. Their pore structures were investigated by physical adsorption of nitrogen. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to characterize surface functional groups. Carbonization of porous benzene phenol polymer at evaluated temperatures transferred the polymer to carbon as proven by X-ray diffraction and transmission electron microscope techniques. The catalytic properties of the solid acids were evaluated using esterification of methanol with acetic acid. Results showed that the catalytic activity for the sulfonated polymer increased with the increase in sulfonation temperature. Sulfonic acid groups on the polymer framework were observed to be more stable than those on the carbon framework.
Yashima et al.
, p. 53 (1979)
Modifying the acidity of H-MOR and its catalytic carbonylation of dimethyl ether
Wang, Meixia,Huang, Shouying,Lü, Jing,Cheng, Zaizhe,Li, Ying,Wang, Shengping,Ma, Xinbin
, p. 1530 - 1537 (2016)
Among the reactions catalyzed by zeolites there are some that exhibit high selectivity due to the spatial confinement effect of the zeolite framework. Tailoring the acidity, particularly the distribution and location of the Br?nsted acid sites in the zeolite is effective for making it a better catalyst for these reactions. We prepared a series of H-mordenite (H-MOR) samples by varying the composition of the sol-gel, using different structure directing agents and post-treatment. NH3-TPD and IR characterization of adsorbed pyridine were employed to determine the amount of Br?nsted acid sites in the 8-membered ring and 12-membered ring channels. It was shown that controlled synthesis was a promising approach to improve the concentration of Br?nsted acid sites in MOR, even with a low Al content. Using an appropriate composition of Si and Al in the sol-gel favored a higher proportion of Br?nsted acid sites in the 8-membered ring channels. HMI as a structure-direct agent gave an obvious enrichment of Br?nsted acid sites in the 8-membered ring. Carbonylation of dimethyl ether was used as a probe reaction to examine the modification of the acid properties, especially the Br?nsted acid sites in the 8-membered ring channels. There was a linear relationship between methyl acetate formation and the number of Br?nsted acid sites in the 8-membered ring channels, demonstrating the successful modification of acid properties. Our results provide information for the rational design and modification of zeolites with spatial constraints.
Effects of metal ions and ligands on transesterification: Synthesis, structures, and catalytic activities of a series of cation-anionic complexes with dipyridylamine ligands
Deng, Yuan,Bai, Ying,Zhu, Long-Guan,Jiang, Jian-Xiong,Lai, Guo-Qiao
, p. 2793 - 2803 (2012)
A series of cation-anion complexes derived by 2,2′-dipyridylamine (Hdpa) and carboxylate ligands with formulas [Ni(Hdpa)2(CH 3COO)]Cl(CH3OH) (1), [Co(Hdpa)2(CH 3COO)]Cl(CH3OH) (2), [Ni(Hdpa)2(CH 3CH2CH2COO)]Cl (3), [Co(Hdpa) 2(CH3CH2CH2COO)]Cl (4), [Ni(Hdpa)2(C6H5COO)]Cl (5), and [Co(Hdpa) 2(C6H5COO)]Cl (6), were synthesized and characterized by IR, elemental analysis, MS(ESI), TG analysis, UV-Vis, and fluorescence spectra. X-ray single crystal structural analysis showed that the coordination geometries of metal ions in these complexes are similar and they are cation-anion species. The hydrogen-bonding structures are 1-D chains through the N-H...Cl bonds. There are weak stacking interactions between pyridine rings in 1-4, while there are no stacking interactions in 5 and 6. We have investigated the transesterification of phenyl acetate with methanol catalyzed by 1-6 under mild conditions; 1-4 are homogeneous catalysts while 5 and 6 are heterogeneous catalysts due to their poor solubility in methanol. Cobalt complexes exhibit higher catalytic activities than corresponding nickel complexes. Complex 4 is the best catalyst of these six complexes.
Site requirements and elementary steps in dimethyl ether carbonylation catalyzed by acidic zeolites
Cheung, Patricia,Bhan, Aditya,Sunley, Glenn J.,Law, David J.,Iglesia, Enrique
, p. 110 - 123 (2007)
Steady-state, transient, and isotopic-exchange studies of dimethyl ether (DME) carbonylation, combined with adsorption and desorption studies of probe molecules and infrared (IR) spectroscopy, were used to identify methyl and acetyl groups as surface intermediates within specific elementary steps involved in the synthesis of methyl acetate from DME-CO mixtures with >99% selectivity on H-zeolites. Carbonylation rates increased linearly with CO pressures but did not depend on DME pressures, suggesting that the addition of CO to CH3 groups present at saturation coverage controls catalytic carbonylation rates. These reactions lead to acetyl groups that subsequently react with DME to form methyl acetate (423-463 K; >99% selectivity) and regenerate methyl intermediates, consistent with kinetic studies of CO reactions with CH3 groups previously formed from DME and with kinetic and IR studies of DME reactions with acetyl groups formed by stoichiometric reactions of acetic anhydride. These studies show that CO reacts with DME-derived intermediates bound on zeolitic Al sites from the gas phase or via weakly held CO species adsorbed non-competitively with CH3 groups. These reactions, in contrast with similar reactions of methanol, occur under anhydrous conditions and avoid the formation of water, which strongly inhibits carbonylation reactions.
Promotion effect of Fe in mordenite zeolite on carbonylation of dimethyl ether to methyl acetate
Zhou, Hui,Zhu, Wenliang,Shi, Lei,Liu, Hongchao,Liu, Shiping,Xu, Shutao,Ni, Youming,Liu, Yong,Li, Lina,Liu, Zhongmin
, p. 1961 - 1968 (2015)
A series of Fe-modified mordenite zeolite samples were synthesized by a template-free method and employed in dimethyl ether (DME) carbonylation reaction for the production of methyl acetate (MAc). XRD, UV-Vis, and UV-Raman characterization studies proved that Fe atoms have been introduced into the mordenite zeolite framework by partial substitution of Al atoms, which led to evident changes of activity and MAc selectivity. With the increase of iron content (as metal) from 0.0 to 3.6 wt%, DME conversion first increased and then decreased. MAc selectivity and catalyst stability were enhanced for all Fe-modified samples. TG and GC-MS analysis of deactivated catalysts showed that the amount of coke retained in the catalysts decreased as the iron content of the zeolites increased. The enhancement effects were expounded in terms of the decrease of the acid strength and acid density in the 12MR channels of mordenite after introduction of Fe, resulting in the reduction of carbon deposition.
The carbonylation of methyl iodide and methanol to methyl acetate catalysed by palladium and platinum iodides
Yang, Jun,Haynes, Anthony,Maitlis, Peter M.
, p. 179 - 180 (1999)
Palladium(II) salts catalyse the carbonylation of methyl iodide in methanol to methyl acetate (5 atm CO, 140°C) in the presence of a large excess of iodide, even without amine or phosphine co-ligands; platinum(II) salts show similar reactions but are a little less effective.
Efficient methanol carbonylation to methyl acetate catalyzed by a cyclic(alkyl)(amino)carbene iridium complex
Hu, Xingbang,Liu, Jia,Liu, Peijun,Shao, Shouyan,Yang, Guoqiang,Zhang, Dejin,Zhang, Zhibing,Zhao, Yue,Zhu, Guisheng
, p. 6045 - 6049 (2020)
An efficient cyclic(alkyl)(amino) carbene iridium complex (C-2) was developed for methanol carbonylation to methyl acetate (MA) directly. Compared with previous results, methanol carbonylation to MA catalyzed byC-2was performed quite well at a low temperature (120 °C). The reaction showed excellent selectivity toward MA (96%) even when the conversion was high (81%). The reaction processes were also investigated by stoichiometric experiments and theoretical calculations.
Carbonylation of dimethyl ether over Co-HMOR
Ma, Meng,Zhan, Ensheng,Huang, Xiumin,Ta, Na,Xiong, Zhiping,Bai, Luyi,Shen, Wenjie
, p. 2124 - 2130 (2018)
Incorporation of Co2+ into the framework of HMOR significantly enhanced the activity for the carbonylation of dimethyl ether to methyl acetate. About 68% of the Co2+ cations are located at site A in the 8-membered ring (8-MR) pores, while 32% of the metal cations are incorporated at site E of the 12-MR pores. Although the amount of the Br?nsted acid sites in the 8-MR pores that are intrinsically active for DME carbonylation decreased considerably upon Co-doping, the conversion of DME increased remarkably, almost doubled. The promotional role of Co2+ in the 8-MR channels was to facilitate the adsorption/activation of both CO and DME molecules. Meanwhile, the Co2+ cations located in the 12-MR channels effectively suppressed coke deposition and thus improved the stability of the Co-HMOR catalyst.
Isolation of cis-dimethyl-(methoxycarbonyl)(triphenylphosphine)gold(III)
Komiya, Sanshiro,Ishikawa, Makoto,Ozaki, Satoshi
, p. 2238 - 2239 (1988)
cis-Dimethyl(methoxycarbonyl)(triphenylphosphine)gold(III) (1) has been prepared by the reaction of carbon monoxide with a mixture of cis-dimethyliodo-(triphenylphosphine)gold(III) and sodium methoxide in methanol. Thermolysis of 1 results in the competitive reductive elimination of methyl acetate and ethane.
Stable ethanol synthesis via dimethyl oxalate hydrogenation over the bifunctional rhenium-copper nanostructures: Influence of support
Chen, Xingkun,Ding, Yunjie,Du, Zhongnan,Li, Zheng,Lin, Ronghe,Wang, Shiyi,Wang, Xuepeng,Zhu, Hejun
, p. 241 - 252 (2022/02/22)
Addition of oxophilc rhenium to decorate small copper nanoparticles has been validated to be an efficient method to prepare a low-copper catalyst for the direct synthesis of ethanol via dimethyl oxalate (DMO) hydrogenation process, and herein we investigated the impact of supports on the catalytic performance of ReCu catalysts. A series of materials including activated carbon (AC), Al2O3, SiO2, TiO2 and ZrO2 were utilized as the support and as prepared Re2Cu5 catalysts were evaluated. The results exhibited that the Re2Cu5/ZrO2 catalyst possesses the highest DMO hydrogenation activity and ethanol yield (~93%), which may be due to its lowest Cu0/Cu+ ratio (0.13), smallest Cu particle size (~0.84 nm) a relative high reduction degree (59%). The CO adsorption behavior characterized by in situ IR spectroscopy showed that a strong metal-support interaction creates an electron deficient environment of Cu nanoparticle, resulting in a lower Cu0/Cu+ ratio that enhances the activation of C[dbnd]O bond in the DMO molecular.
Synthesis, Characterisation, and Determination of Physical Properties of New Two-Protonic Acid Ionic Liquid and its Catalytic Application in the Esterification
Shahnavaz, Zohreh,Zaharani, Lia,Khaligh, Nader Ghaffari,Mihankhah, Taraneh,Johan, Mohd Rafie
, p. 165 - 172 (2020/10/26)
A new ionic liquid was synthesised, and its chemical structure was elucidated by FT-IR, 1D NMR, 2D NMR, and mass analyses. Some physical properties, thermal behaviour, and thermal stability of this ionic liquid were investigated. The formation of a two-protonic acid salt namely 4,4′-trimethylene-N,N′-dipiperidinium sulfate instead of 4,4′-trimethylene-N,N′-dipiperidinium hydrogensulfate was evidenced by NMR analyses. The catalytic activity of this ionic liquid was demonstrated in the esterification reaction of n-butanol and glacial acetic acid under different conditions. The desired acetate was obtained in 62-88 % yield without using a Dean-Stark apparatus under optimal conditions of 10 mol-% of the ionic liquid, an alcohol to glacial acetic acid mole ratio of 1.3: 1.0, a temperature of 75-100°C, and a reaction time of 4 h. α-Tocopherol (α-TCP), a highly efficient form of vitamin E, was also treated with glacial acetic acid in the presence of the ionic liquid, and O-acetyl-α-tocopherol (Ac-TCP) was obtained in 88.4 % yield. The separation of esters was conducted during workup without the utilisation of high-cost column chromatography. The residue and ionic liquid were used in subsequent runs after the extraction of desired products. The ionic liquid exhibited high catalytic activity even after five runs with no significant change in its chemical structure and catalytic efficiency.
Oxidative Addition of a Hypervalent Iodine Compound to Cycloplatinated(II) Complexes for the C–O Bond Construction: Effect of Cyclometalated Ligands
Dadkhah Aseman, Marzieh,Nikravesh, Mahshid,Abbasi, Alireza,Shahsavari, Hamid R.
supporting information, p. 18822 - 18831 (2021/12/13)
The complex [PtMe(Obpy)(OAc)2(H2O)], 2a, Obpy = 2,2′-bipyridine N-oxide, is prepared through the reaction of [PtMe(Obpy)(SMe2)], 1a, by 1 equiv of PhI(OAc)2 via an oxidative addition (OA) reaction. Pt(IV) complex 2a attends the process of C–O bond reductive elimination (RE) reaction to form methyl acetate and corresponding Pt(II) complex [Pt(Obpy)(OAc)(H2O)], 3a. The kinetic of OA and RE reactions are investigated by means of different spectroscopies. The obtained results show that the reaction rates of OA step of 1a are faster than its analogous complex [PtMe(ppy)(SMe2)], 1b, ppy = 2-phenylpyridine. The density functional theory (DFT) calculations signify that the OA reaction initiated by a nucleophilic attack of the platinum(II) central atom of 1b on the iodine(III) atom while it had commenced by a nucleophilic substitution reaction of coordinated SMe2 in 1a with a carbonyl oxygen atom of PhI(OAc)2. Our calculation revealed that the key step for 1a is an acetate transfer from the I(III) to Pt(II) through a formation of square pyramidal iodonium complex. This can be attributed to the more electron-withdrawing character of Obpy ligand than to ppy which reduces the nucleophilicity of Pt atom in 1a. Furthermore, 2a with electron-withdrawing Obpy ligand prone to C–O bond formation faster than complex [PtMe(ppy)(OAc)2(H2O)], 2b, with an electron-rich ppy ligand which conforms to the anticipation that REs occur faster on electron-poor metal centers.