Alcohol elastomer based on superabsorbents

A microporous superabsorbent of poly(acrylic acid‐g‐cetyltrimethylammonium bromide) (PAA‐g‐CTAB) is synthesized by aqueous polymerization method. With the use of the superabsorbent as a host backbone, a large amount of alcohol is absorbed inside the micropores of PAA‐g‐CTAB to form an alcohol elastomer with an alcohol absorbency of 32 g/g. As a new kind of quasi‐solid‐state fuel, the alcohol elastomer is safe, low cost, and easy to use. The alcohol absorbency of the superabsorbent and the combustion properties of the alcohol elastomer can be adjusted by tuning the polymerization reaction conditions. The flame reactions in the alcohol elastomer arouse more interest for the alcohol elastomer. Copyright © 2011 John Wiley & Sons, Ltd.     

Highly Efficient Direct Aerobic Oxidative Esterification of Cinnamyl Alcohol with Alkyl Alcohols Catalysed by Gold Nanoparticles Incarcerated in a Nanoporous Polymer Matrix: A Tool for Investigating the Role of the Polymer Host

The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi‐block copolymer matrix, which consisted of syndiotactic polystyrene‐co‐cis‐1,4‐polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base‐catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10–45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2‐propanol, 1‐butanol, 1‐hexanol or 1‐octanol. The rate constants of the latter reaction are pseudo‐zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (E_a) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1‐butanol (E_a=57.8±11.5 and 62.7±16.7 kJ mol^?1 for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2‐phenylethanol follows pseudo‐first‐order kinetics with respect to 2‐phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction.     

The kinetics of a negative‐tone acrylic photoresist for 193‐nm lithography

Polymethacrylates with tert‐alcohol ester were synthesized as negative‐tone chemical amplification photoresists (CAMPs) for 193‐nm microlithography. The acid‐catalyzed dehydration reaction of the CAMPs was analyzed via Fourier transform infrared. The crosslinking behavior following the dehydration reaction of the exposed CAMPs made it possible for them to be used as negative‐tone photoresists. During the postexposure‐baking process of the resists, the decay of the active proton concentration due to the evaporation and trapping of the active acid was lumped to a time constant (τ). Kinetic studies revealed this dehydration reaction was the first order to the hydroxy group and proton concentration. The introduction of the isobornyl methacrylate monomer into the resists produced a higher glass‐transition temperature as well as a higher reactive ion etching resistance. The lithographic performance was investigated by use of isopropyl alcohol as a developer under various processing conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 954–961, 2000     

Oxygen‐Assisted Hydroxymatairesinol Dehydrogenation: A Selective Secondary‐Alcohol Oxidation over a Gold Catalyst

Selective dehydrogenation of the biomass‐derived lignan hydroxymatairesinol (HMR) to oxomatairesinol (oxoMAT) was studied over an Au/Al₂O₃ catalyst. The reaction was carried out in a semi‐batch glass reactor at 343 K under two different gas atmospheres, namely produced through synthetic air or nitrogen. The studied reaction is, in fact, an example of secondary‐alcohol oxidation over an Au catalyst. Thus, the investigated reaction mechanism of HMR oxidative dehydrogenation is useful for the fundamental understanding of other secondary‐alcohol dehydrogenation over Au surfaces. To investigate the elementary catalytic steps ruling both oxygen‐free‐ and oxygen‐assisted dehydrogenation of HMR to oxoMAT, the reactions were mimicked in a vacuum over an Au₂₈ cluster. Adsorption of the involved molecular species—O₂, three different HMR diastereomers (namely, one SRR and two RRR forms), and the oxoMAT derivative—were also studied at the DFT level. In particular, the energetic and structural differences between SRR‐HMR and RRR‐HMR diastereomers on the Au₂₈ cluster were analyzed, following different reaction pathways for the HMR dehydrogenation that occur in presence or absence of oxygen. The corresponding mechanisms explain the higher rates of the experimentally observed oxygen‐assisted reaction, mostly depending on the involved HMR diastereomer surface conformations. The role of the support was also elucidated, considering a very simple Au₂₈ charged model that explains the experimentally observed high reactivity of the Au/Al₂O₃ catalyst.     

Brønsted Acid Catalyzed Morita–Baylis–Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI‐MS(/MS) Monitoring and DFT Calculations

A Morita–Baylis–Hillman (MBH) reaction catalyzed by thiourea was monitored by ESI‐MS(/MS) and key intermediates were intercepted and characterized. These intermediates suggest that thiourea acts as an organocatalyst in all steps of the MBH reaction cycle, including the rate‐limiting proton‐transfer step. DFT calculations, performed for a model MBH reaction between formaldehyde and acrolein with trimethylamine as base and in the presence or the absence of thiourea, suggest that thiourea accelerates MBH reactions by decreasing the transition‐state (TS) energies through bidentate hydrogen bonding throughout the whole catalytic cycle. In the rate‐limiting proton‐transfer step, the thiourea acts not as a proton shuttle, but as a Brønsted acid stabilizing the basic oxygen center that is formed in the TS.     

羊毛-Pd(0)催化剂的制备、表征及其在水相中对醇的催化氧化反应

以天然生物高分子羊毛为载体,成功制备了负载型Pd(0)催化剂.采用电场发射扫描电镜和光电子能谱等方法对催化剂进行了表征.结果表明,Pd(0)颗粒均匀地分散在羊毛表面.将羊毛-Pd(0)催化剂用于醇氧化反应,考察了催化剂用量、碱类型和用量、反应温度及时间等因素对反应性能的影响.实验发现,在水相中,35mg羊毛-Pd(0)催化剂在0.2mmol的K2CO3存在下,可以高选择性地将0.2mmol的醇转化为相应的醛或酮,且该催化剂具有很好的重复使用性能.     

多金属氧酸盐催化苯甲醇的选择性氧化：一个绿色可循环的高效催化氧化体系

以Keggin结构的几类杂多酸和三乙胺（TEA）为原料,通过简单的酸碱反应合成了相应杂多酸的TEA盐。 并以它们作为催化剂,30％H2O2作氧化剂,在不使用长链相转移剂的条件下,研究了它们催化苯甲醇选择氧化制备苯甲醛的反应性能。 结果表明,该类催化剂在苯甲醇的选择氧化反应中具有比相应杂多酸更高的催化活性或选择性。 其中[TEAH]H2PW12O40为最佳催化剂,在适宜的反应条件下,该催化剂上苯甲醇转化率可达99.5％以上,苯甲醛选择性达~100％。 催化剂可以被分离和循环使用多次,活性、选择性基本不变。 用水作溶剂,避免了有机溶剂的使用,是一个高效、绿色的苯甲醛选择氧化体系。     

Alcohol and proton transport in perfluorinated ionomer membranes for fuel cells

To clarify the transport mechanisms of alcohols and proton in perfluorosulfonated ionomer (PFSI) membranes for fuel cells, four membranes having different equivalent weight (EW) values were examined. Membranes were immersed in methanol, ethanol, and 2-propanol to prepare a total of 12 samples, and membrane swelling, mass (alcohol and proton) transports, and interactions between alcohols and proton were investigated systematically in the fully penetrated state. The membrane expansion fraction theta and alcohol content lambda increased with decreasing the EW value for all the samples. The self-diffusion coefficients (D's) of the alkyl group and of OH (including protons) were measured separately by the pulsed-gradient spin-echo (PGSE)-NMR method and the D's also increased with decreasing the EW value. These results implied that the alcohols penetrate into the hydrophilic regions of the PFSI membranes and diffuse through the space expanded by the alcohols. The ionic cluster regions formed by the alcohols resemble those induced by water in the water swollen membrane, where protons dissociated from sulfonic acid groups transport through the regions together with water molecules. The D values decreased with increasing the molecular weight of alcohols. This trend was supported by activation energies Ea estimated from the Arrhenius plots of D in the temperature range from 30 to -40 degrees C. The PGSE-NMR measurements also revealed that protons move faster than the alkyl groups in the membranes. The proton transport by the Grotthuss (hopping) mechanism was facilitated by the increase of the alcohol content and the decrease of the molecular weight. This result was also supported by the experimental results of proton conductivity kappa and mobility u(H(+)). Density functional theory (DFT) calculations of the interaction energy DeltaE(int) between proton and alcohol (including OH) showed that the /DeltaE(int)/ increases with increasing the molecular weight of alcohols, which is in a inverse relationship with the kappa and u(H(+)) values. The proton transport depends strongly on the DeltaE(int) in the membranes.     

In Situ Solid‐State Reactions Monitored by X‐ray Absorption Spectroscopy: Temperature‐Induced Proton Transfer Leads to Chemical Shifts

The dramatic colour and phase alteration with the solid‐state, temperature‐dependent reaction between squaric acid and 4,4′‐bipyridine has been probed in situ with X‐ray absorption spectroscopy. The electronic and chemical sensitivity to the local atomic environment through chemical shifts in the near‐edge X‐ray absorption fine structure (NEXAFS) revealed proton transfer from the acid to the bipyridine base through the change in nitrogen protonation state in the high‐temperature form. Direct detection of proton transfer coupled with structural analysis elucidates the nature of the solid‐state process, with intermolecular proton transfer occurring along an acid‐base chain followed by a domino effect to the subsequent acid‐base chains, leading to the rapid migration along the length of the crystal. NEXAFS thereby conveys the ability to monitor the nature of solid‐state chemical reactions in situ, without the need for a priori information or long‐range order.     

Influence of Ions on Aqueous Acid–Base Reactions

We study the effects of bromide salts on the rate and mechanism of the aqueous proton/deuteron‐transfer reaction between the photoacid 8‐hydroxy‐1,3,6‐pyrenetrisulfonic acid (HPTS) and the base acetate. The proton/deuteron release is triggered by exciting HPTS with 400 nm femtosecond laser pulses. Probing the electronic and vibrational resonances of the photoacid, the conjugate photobase, the hydrated proton/deuteron and the accepting base with femtosecond visible and mid‐infrared pulses monitors the proton transfer. Two reaction channels are identified: 1) direct long‐range proton transfer over hydrogen‐bonded water bridges that connect the acid and base and 2) acid dissociation to produce fully solvated protons followed by proton scavenging from solution by acetate. We observe that the addition of salt affects the long‐range reaction pathway, and reduces both the rate at which protons are released to solution by HPTS and the rate at which solvated protons are scavenged from solution by acetate. We study the dependence of these effects on the nature and concentration of the dissolved salt.     

Indium‐promoted Conversion of Allylic Bromide to Alcohol Moiety and Synthesis of Pipermethystine Skeletons

Dihydropyridone bromide ( 2 ) was converted to the corresponding alcohol ( 1 ) by reaction with indium in air or with indium followed by treatment with a sulfonyloxaziridine. The alcohol ( 1 ) was transformed in four steps to a phenylsulfone‐substituted pipermethystine derivative ( 10 ). Reductive cleavage of the phenylsulfone did not yield the pipermethystine natural product. Several new pyridone derivatives were synthesized.     

醇脱氢酶结构和作用机理研究进展

介绍了醇脱氢酶的种类, 酵母醇脱氢酶和肝醇脱氢酶等两类常用的醇脱氢酶的物理化学性质和活性位点结构. 归纳了对肝醇脱氢酶和酵母醇脱氢酶作用机理的研究, 重点评述了醇脱氢酶催化反应中的两个关键步骤质子转移和氢化物转移过程机理的研究进展.     

An Efficient Approach for the Synthesis of 1,1‐bis(2‐phenyl‐3‐indolyl)ethylene Using ZnO Nanocatalyst

A combination of nanocatalyst and green chemical route (mechanochemistry) was used to generate a series of substituted 1,1‐bis(2‐phenyl‐3‐indolyl)ethylene derivatives ( 4a–e ) that were synthesized by reacting various 2‐arylindoles ( 1a–e ) and acetyl chloride in absolute alcohol with or without ZnO nano as catalyst via two approaches, that is, classical and green solvent‐free route. The use of ZnO nano particles is preferred to absence of catalyst in terms of short reaction time and mild reaction conditions with reusability of the catalyst. All the synthesized compounds were characterized on the basis of their elemental and spectral data (IR, proton magnetic resonance, ¹³C NMR, and Mass).     

Hydrogen-bond configuration in hydrogen-bond solutions. 1. Alcohol/alcohol solutions

A theory based on the hydrogen-bond configuration is proposed and applied to alcohol/alcohol binary solutions. The theory leads explicit expressions for the mixing Gibbs energy and reproduces the experiments on the crystal–liquid phase-diagrams of pure crystals and co-crystals and mixing heats with the parameters common to these experiments. The mixing entropy arises from the increase in the hydrogen-bonding availability of proton donors to approach hydrogen-bond-free proton acceptors. The mixing heat arises from a balance between the contribution from maintaining the original associations in pure liquids and the contribution from a construction of hydrogen bonds freely to hydrogen-bond-free acceptors. When hydrogen-bond associations between component-1 and component-2 are distinguished statistically from associations in each pure component, we call the solution as a cooperative solution that has at least one stoichiometric cooperative concentration point. Some shorter alcohol/alcohol solutions and some aromatic alcohol/aromatic alcohol solutions, however, have no cooperative point and we call those solutions as the ideal hydrogen-bond solutions of which properties are mainly governed by the ideal-gas-like mixing hydrogen-bond entropy. The hydrogen-bond energies of various combinations of the proton acceptor and the proton donor have been estimated consistently from the fittings of the theory, the shifts by hydrogen bonding of the OH stretching in the Raman or IR spectroscopy, and the sublimation energy of crystals. The present theory reveals the characteristics of hydrogen-bond solutions and gives some predictions.     

Computational analysis of the proton translocation from Asp96 to schiff base in bacteriorhodopsin

The potential energy change during the M --> N process in bacteriorhodopsin has been evaluated by ab initio quantum chemical and advanced quantum chemical calculations following molecular dynamics (MD) simulations. Many previous experimental studies have suggested that the proton transfer from Asp96 to the Schiff base occurs under the following two conditions: (1) the hydrogen bond between Thr46 and Asp96 breaks and Thr46 is detached from Asp96 and (2) a stable chain of four water molecules spans an area from Asp96 --> Schiff base. In this work, we successfully reproduced the proton-transfer process occurring under these two conditions by molecular dynamics and quantum chemical calculations. The quantum chemical computation revealed that the proton transfer from Asp96 to Shiff base occurs in two-step reactions via an intermediate in which an H(3)O(+) appears around Ala215. The activation energy for the proton transfer in the first reaction was calculated to be 9.7 kcal/mol, which enables fast and efficient proton pump action. Further QM/MM (quantum mechanical/molecular mechanical) and FMO (fragment molecular orbital) calculations revealed that the potential energy change during the proton transfer is tightly regulated by the composition and the geometry of the surrounding amino acid residues of bacteriorhodopsin. Here, we report in detail the Asp96 --> Schiff base proton translocation mechanism of bacteriorhodopsin. Additionally, we discuss the effectiveness of combining quantum chemical calculations with truncated cluster models followed by advanced quantum chemical calculations applied to a whole protein to elucidate its reaction mechanism.     

Proton‐Transfer Reactions of Acridine in Water‐Containing Ionic‐Liquid‐Rich Mixtures

To assess the potential of ionic liquids (ILs) as a solubilizing media that facilitates proton‐transfer reactions, acridine prototropism is investigated using UV/Vis molecular absorbance as well as steady‐state and time‐resolved fluorescence with different ILs in the presence of a small amount of dilute acid or base. It is found that protonation and deprotonation of acridine, when dissolved in different ILs, can be triggered by the addition of a small amount of dilute aqueous HCl and NaOH, respectively, in both the ground and excited states, irrespective of the identity of the IL. However, the amount of dilute acid/base needed to protonate/deprotonate acridine dissolved in different ILs is found to vary from one IL to another. Steady‐state fluorescence measurements also imply the presence of interactions between the acidic proton(s) of IL cation and excited acridine. The interconversion of neutral and protonated acridine, as well as the presence of a weakly fluorescent complex between excited acridine and the acidic proton(s) of the IL cation, is further corroborated by the parameters recovered from the fitting of the excited‐state intensity‐decay data. It is established that ILs as solubilizing media readily support facile proton transfer in both ground and excited states.     

Circularly Polarized Luminescence of Aluminum Complexes for Chiral Sensing of Amino Acid and Amino Alcohol

Determination of the absolute configuration (AC) of chiral molecules is a key issue in many fields related to chirality such as drug development, the asymmetric reaction screening, and the structure determination of natural compounds. Although various methods, such as X‐ray crystallography and NMR spectroscopy, are used to determine the AC, a simple and cheap alternative method is always anticipated. So far, electronic circular dichroism (ECD) spectroscopy has been widely used to ascertain the AC and enantiomeric excess (ee) values by applying appropriate organic probes. Here, circularly polarized luminescence (CPL) spectroscopy was applied to determine the AC and ee values of a series of amino acid and amino alcohol. The measurements were conducted by mixing the amino acids or amino alcohols with an achiral 1‐hydroxy‐2‐naphthaldehyde. Upon in situ formation of the Schiff base complexes, the system showed emission enhancement and CPL in the presence of Al³⁺, whose intensity and sign can be used to assign the chiral sense of the amino acids and amino alcohols. The authenticity of the method was further compared with the established CD spectroscopy, revealing that CPL spectra of formed Al³⁺ complex were effective to determine the AC of chiral species.     

Ti-MWW分子筛上烯丙醇环氧化制环氧丙醇

 以哌啶为模板剂, 硼酸为结构承载助剂,采用动态水热法成功地合成了Ti-MWW层状前体,经酸处理和煅烧后,得到Ti-MWW分子筛. 紫外-可见光谱表明, Ti-MWW层状前体中含有四面体和八面体配位的钛物种. 酸处理可以很容易地将非骨架的八面体钛脱除,煅烧后分子筛不含锐钛矿相; 未经酸处理直接煅烧,部分八面体钛会聚集形成锐钛矿相. Ti-MWW层状前体的红外光谱在960 cm-1处没有骨架钛的特征吸收谱带出现,经酸处理后,该特征吸收峰出现. 以H2O2为氧化剂,考察了Ti-MWW分子筛上的烯丙醇环氧化性能,发现凝胶Si/Ti=20, 15%HNO3处理12～16 h的情况下,制得的Ti-MWW的催化性能最好,在温度为333 K和反应时间为30 min, 转化率为88.7%, 选择性为99%; 但酸处理时间过长可使部分Ti-MWW中的钛生成锐钛矿相,从而导致催化剂活性下降.     

Asymmetric Cascade Reaction to Allylic Sulfonamides from Allylic Alcohols by Palladium(II)/Base‐Catalyzed Rearrangement of Allylic Carbamates

A regio‐ and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl‐protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step‐economy with operational simplicity (e.g. no need for inert‐gas atmosphere or catalyst activation). Mechanistic studies support a Pd^II‐catalyzed [3,3] rearrangement of allylic carbamates—generated in situ from the allylic alcohol and an isocyanate—as the key step, which is followed by a decarboxylation.