Kinetics of liquid phase synthesis of ethyl tert‐butyl ether from tert‐butyl alcohol and ethanol catalyzed by β‐zeolite supported on monolith

This paper compared the performance of β‐zeolite and Amberlyst‐15 catalysts on a liquid phase synthesis of ethyl tert‐butyl ether (ETBE) from ethanol (EtOH) and tert‐butyl alcohol (TBA) β‐Zeolite was synthesized and deposited on monolith support. Its structure was confirmed by an XRD measurement and its composition was analyzed by an XRF measurement. It was found that even though the catalytic activity of β‐zeolite was lower than that of Amberlyst‐15, the selectivity of ETBE was much higher than that of Amberlyst‐15, resulting in almost the same level of ETBE yield. The dehydration of TBA to isobutene (IB) was the major side reaction. The kinetic study of the reaction catalyzed by β‐zeolite supported on monolith was carried out by using a semibatch reactor. The effect of external mass transfer was investigated by varying stirring speeds. The activity‐based rate expressions were developed taking into account of water inhibition. Three temperature levels of 323, 333, and 343 K were performed in the study to obtain the parameters in the Arrhenius's equation and the Van't Hoff's equation. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 292–299, 2002     

Simultaneous measurement of methyl tert‐butyl ether and tert‐butyl alcohol in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry

The abundant production of methyl tert‐butyl ether (MTBE) and its widespread use have led to an increase in the potential for human exposure. This work described a simple, fast, sensitive, reliable and low‐cost method for the simultaneous measurement of MTBE and its metabolite, tert‐butyl alcohol (TBA) in human serum by headspace solid‐phase microextraction gas chromatography–mass spectrometry. Extraction conditions were optimized and 40 °C, 10 min, 250 rpm and 0.3 g NaCl for a 1 mL sample were the optimal conditions. This method showed good analytical performance in terms of sensitivity with limits of detection in serum (1 mL) of 0.03 µg/L for MTBE and 0.05 µg/L for TBA, accuracy (mean recovery values) from 75.8% to 85.8%, precision (relative standard deviations) <10% and sample stability (biodegradation) <10% after 28 days. A verification experiment proved the reproducibility and stability of this method as well. Finally the method was used to detect 212 specimens, and the internal dose levels for MTBE in human serum were presented in China. Copyright © 2015 John Wiley & Sons, Ltd.     

Di‐tert‐butyl ketone hydrazone and di‐tert‐butyl ketone triphenyl­phosphoranyl­idene­hydrazone

Reaction of di‐tert‐butyl ketone with hydrazine hydrate gives di‐tert‐butyl ketone hydrazone, C₉H₂₀N₂, which is dimerized by double hydrogen bonding in the solid state. Further reaction of this compound with dibromo­triphenyl­phospho­rane gives di‐tert‐butyl ketone triphenyl­phosphoranyl­idene­hydrazone, C₂₇H₃₃N₂P, in the structure of which double chains parallel to the c axis are formed through weak C—H⋯π and π–π stacking inter­actions. The hydrazone group is nearly planar in both cases. In the second compound, one of the aromatic rings is nearly coplanar with the hydrazone moiety, indicating possible π‐conjugation.     

Anomalous solubility of polyacrylamide prepared by dispersion (precipitation) polymerization in aqueous tert‐butyl alcohol

Polyacrylamide prepared by dispersion (precipitation) polymerization in an aqueous t‐butyl alcohol (TBA) medium is only partially soluble when the TBA concentrations in the polymerization media are in the range 82 vol % < TBA < 95 vol %. Independent experiments with a soluble (linear) sample of polyacrylamide show that the polymer swells sufficiently in the aforementioned media to lower the glass‐transition temperature of the polymer below the polymerization temperature (50 °C). The anomalous solubility has been attributed to the crosslinking of polymer chains that occurs during the solid‐phase polymerization of acrylamide in the swollen polymer particles. It is postulated that some of the radical centers shift from the chain end to the chain backbone during solid‐phase polymerization by chain transfer to neighboring polymer molecules, and when pairs of such radicals come into close vicinity, crosslinking occurs. However, dispersion (precipitation) polymerization in other media such as aqueous methanol and aqueous acetone yields polymers that are soluble. This result has been attributed to the fact that the polymer radical undergoes a chain‐transfer reaction with these solvents at a much faster rate than with TBA, which overcomes the effect of the polymer‐transfer reaction. Even the addition of as little as 5% methanol to a TBA–water mixture (TBA:water = 85:10) gives rise to a soluble polymer. The chain‐transfer constants for acetone, methanol, and TBA have been determined to be 9.0 × 10^?6, 6.9 × 10^?6, and 1.48 × 10^?6, respectively, at 50 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3434–3442, 2001     

离子交换树脂催化酯化生物油的试验研究

生物油黏稠、稳定性差、热值低、腐蚀性强,需要进行改质与品位提升,将生物油中的有机酸通过酯化的方法转化为中性的酯类可以改善生物油的性能。实验利用模型反应,筛选出了适合于生物油体系的732型和NKC-9型两种树脂作为酯化改质的催化剂。生物油和甲醇在间歇釜内以732和NKC-9为催化剂进行改质以后,酸值分别降低了88.54%和85.95%,表明生物油中的有机酸极大地转化为中性酯类。此外,热值分别提高了32.26%和31.64%,水分分别降低了27.74%和30.87%,密度均降低了21.77%,黏度降低均接近97%。732树脂固定床催化酯化生物油后,酸值降低了92.61%。加速陈化实验和铝片腐蚀性实验结果分别表明,改质生物油的稳定性和腐蚀性能得到了改善。     

Atmospheric chemistry of isopropyl formate and tert‐butyl formate

Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH₃)₂, and tert‐butyl formate, HC(O)OC(CH₃)₃. Product distributions are reported from both Cl‐ and OH‐initiated oxidation, and reaction mechanisms are proposed to account for the observed products. The proposed mechanisms include examples of the α‐ester rearrangement reaction, novel isomerization pathways, and chemically activated intermediates. The atmospheric oxidation of isopropyl formate by OH radicals gives the following products (molar yields): acetic formic anhydride (43%), acetone (43%), and HCOOH (15–20%). The OH radical initiated oxidation of tert‐butyl formate gives acetone, formaldehyde, and CO₂ as major products. IR absorption cross sections were derived for two acylperoxy nitrates derived from the title compounds. Rate coefficients are derived for the kinetics of the reactions of isopropyl formate with OH (2.4 ± 0.6) × 10^?12, and with Cl (1.75 ± 0.35) × 10^?11, and for tert‐butyl formate with Cl (1.45 ± 0.30) × 10^?11 cm³ molecule^?1 s^?1. Simple group additivity rules fail to explain the observed distribution of sites of H‐atom abstraction for simple formates. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 479–498, 2010     

Favoured conformations of methyl isopropyl,ethyl isopropyl,methyl tert‐butyl,and ethyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate

The conformations of organic compounds determined in the solid state are important because they can be compared with those in solution and/or from theoretical calculations. In this work, the crystal and molecular structures of four closely related diesters, namely methyl isopropyl 2‐(triphenylphosphoranylidene)malonate, C₂₅H₂₅O₄P, ethyl isopropyl 2‐(triphenylphosphoranylidene)malonate, C₂₆H₂₇O₄P, methyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate, C₂₆H₂₇O₄P, and ethyl tert‐butyl 2‐(triphenylphosphoranylidene)malonate, C₂₇H₂₉O₄P, have been analysed as a preliminary step for such comparative studies. As a result of extensive electronic delocalization, as well as intra‐ and intermolecular interactions, a remarkably similar pattern of preferred conformations in the crystal structures results, viz. a syn–anti conformation of the acyl groups with respect to the P atom, with the bulkier alkoxy groups oriented towards the P atom. The crystal structures are controlled by nonconventional hydrogen‐bonding and intramolecular interactions between cationoid P and acyl and alkoxy O atoms in syn positions.     

离子交换树脂催化合成碳酸亚丙酯

碘型离子交换树脂在某些偶极非质子性溶剂的作用下，能有效地催化二氧化碳与环氧丙烷合成碳酸亚丙酯，并能重复使用至少10次而仍能保持较高的催化活性。     

Oxidation of alkanes and secondary alcohols to ketones with tert‐butyl hydroperoxide catalyzed by a water‐soluble ruthenium complex under solvent‐free conditions

An easily synthesized water‐soluble ruthenium complex, [C₆H₅CH₂N(CH₃)₂H]₂[Ru(dipic)Cl₃] (dipic =2,6‐pyridinedicarboxylate), as a catalyst showed high efficiency in the oxidation of alkanes and secondary alcohols to their corresponding ketones under solvent‐free and low‐catalyst‐loading conditions. This catalytic system could tolerate a variety of substrates and gave the corresponding ketones in good to excellent yields. The products were easily separated and purified due to the water solubility of the ruthenium complex.     

A di‐tert‐butyl acrylate monomer for controlled radical photopolymerization

A new di‐tert‐butyl acrylate (diTBA) monomer for controlled radical polymerization is reported. This monomer complements the classical use of tert‐butyl acrylate (TBA) for synthesis of poly(acrylic acid) by increasing the density of carboxylic acids per repeat unit, while also increasing the flexibility of the carboxylic acid side‐chains. The monomer is well behaved under Cu(II)‐mediated photoinduced controlled radical polymerization and delivers polymers with excellent chain‐end fidelity at high monomer conversions. Importantly, this new diTBA monomer readily copolymerizes with TBA to further the potential for applications in areas such as dispersing agents and adsorbents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 801–807     

Depolymerization kinetics of di(4‐tert‐butyl cyclohexyl) itaconate and Mark‐Houwink‐Kuhn‐Sakurada parameters of di(4‐tert‐butyl cyclohexyl) itaconate and di‐n‐butyl itaconate

Multipulse pulsed laser polymerization coupled with size exclusion chromatography (MP‐PLP‐SEC) has been employed to study the depropagation kinetics of the sterically demanding 1,1‐disubstituted monomer di(4‐tert‐butylcyclohexyl) itaconate (DBCHI). The effective rate coefficient of propagation, k, was determined for a solution of monomer in anisole at concentrations, c, 0.72 and 0.88 mol L^?1 in the temperature range 0 ≤ T ≤ 70 °C. The resulting Arrhenius plot (i.e., ln k vs. 1/RT) displayed a subtle curvature in the higher temperature regime and was analyzed in the linear part to yield the activation parameters of the forward reaction. In the temperature region where no depropagation was observed (0 ≤ T ≤ 50 °C), the following Arrhenius parameters for k_p were obtained (DBCHI, E_p = 35.5 ± 1.2 kJ mol^?1, ln A_p = 14.8 ± 0.5 L mol^?1 s^?1). In addition, the k data was analyzed in the depropagatation regime for DBCHI, resulting in estimates for the associated entropy (?ΔS = 150 J mol^?1 K^?1) of polymerization. With decreasing monomer concentration and increasing temperature, it is increasingly more difficult to obtain well structured molecular weight distributions. The Mark Houwink Kuhn Sakurada (MHKS) parameters for di‐n‐butyl itaconate (DBI) and DBCHI were determined using a triple detection GPC system incorporating online viscometry and multi‐angle laser light scattering in THF at 40 °C. The MHKS for poly‐DBI and poly‐DBCHI in the molecular weight range 35–256 kDa and 36.5–250 kDa, respectively, were determined to be K_DBI = 24.9 (10³ mL g^?1), α_DBI = 0.58, K_DBCHI = 12.8 (10³ mL g^?1), and α_DBCHI = 0.63. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1931–1943, 2007     

Kinetic study of the ruthenium(VI)‐catalyzed oxidation of benzyl alcohol by alkaline hexacyanoferrate(III)

The kinetics of the Ru(VI)‐catalyzed oxidation of benzyl alcohol by hexacyanoferrate(III), in an alkaline medium, has been studied using a spectrophotometric technique. The initial rates method was used for the kinetic analysis. The reaction is first order in [Ru(VI)], while the order changes from one to zero for both hexacyanoferrate(III) and benzyl alcohol upon increasing their concentrations. The rate data suggest a reaction mechanism based on a catalytic cycle in which ruthenate oxidizes the substrate through formation of an intermediate complex. This complex decomposes in a reversible step to produce ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in a slow step. The theoretical rate law obtained is in complete agreement with all the experimental observations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 421–429, 2002     

Reactions of Di(tert‐butyl)diazomethane with Acceptor‐Substituted Ethylenes

Di(tert‐butyl)diazomethane ( 4 ) is a nucleophilic 1,3‐dipole with strong steric hindrance at one terminus. In its reaction with 2,3‐bis(trifluoromethyl)fumaronitrile ((E)‐ BTE ), a highly electrophilic tetra‐acceptor‐substituted ethene, an imino‐substituted cyclopentene 9 is formed as a 1 : 2 product. The open‐chain zwitterion 10 , assumed as intermediate, adds the second molecule of (E)‐ BTE . The ¹⁹F‐ and ¹³C‐NMR spectra allow the structural assignment of two diastereoisomers, 9A and 9B . The zwitterion 10 can also be intercepted by dimethyl 2,3‐dicyanofumarate ( 11 ) and furnishes diastereoisomeric cyclopentenes 12A and 12B ; an X‐ray‐analysis of 12B confirms the ‘mixed’ 1 : 1 : 1 product. Competing is an (E)‐ BTE ‐catalyzed decomposition of 4 to give 2,3,4,4‐tetramethylpent‐1‐ene ( 7 )+N₂; the reaction of (E)‐ BTE with a trace of water appears to be responsible for the chain initiation. The H₂SO₄‐catalyzed decomposition of diazoalkane 4 , indeed, produced the alkene 7 in high yield. The attack on the hindered diazoalkane 4 by 11 is slower than that by (E)‐ BTE ; the zwitterionic intermediate 21 undergoes cyclization and furnishes the tetrasubstituted furan 22 . In fumaronitrile, electrophilicity and steric demand are diminished, and a 1,3‐cycloaddition produces the 4,5‐dihydro‐1H‐pyrazole derivative 25 . The reaction of 4 with dimethyl acetylenedicarboxylate leads to pyrazole 29 +isobutene.     

Kinetic study of transesterification of methyl acetate with n‐butanol catalyzed by NKC‐9

The transesterification of methyl acetate and n‐butanol catalyzed by cation‐exchange resin, NKC‐9, was studied in this work to obtain the reaction kinetics. The experiments were carried out in a stirred batch reactor at different temperatures (328.15, 333.15, 338.15, 343.15, 345.15 K) under atmospheric pressure. The effects of temperature, molar ratio of reactants, and catalyst loading on the reaction rate were researched under the condition of eliminating the effect of diffusion. The experimental data were correlated with a kinetic model based on the pseudo‐homogeneous catalysis. The kinetic equation describing the reaction catalyzed by NKC‐9 was developed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 101–106, 2009     

Kinetic study of the stable free‐radical copolymerization of styrene with butyl methacrylate

The radical copolymerization of styrene and n‐butyl methacrylate mediated by 1‐phenyl‐1‐(2′,2′,6′,6′‐tetramethyl‐1′‐piperidinyl‐oxy)ethane in bulk at 125 °C has been analyzed over a wide range of conversions and monomer feed compositions. Monomer reactivity ratios have been determined, and the Mayo–Lewis terminal model provides excellent predictions for the variations of the intermolecular structure over the entire conversion range. The kinetic analysis of this copolymerization system indicates an apparent propagation rate coefficient independent of the monomer feed composition as well as a limiting conversion that decreases as the styrene monomer feed decreases. This fact is attributed to side reactions leading to unsaturated end groups and the accumulation of nonactive adducts of n‐butyl methacrylate. The number‐average molecular weights linearly increase with conversion, and the copolymers present narrow molecular weight distributions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2750–2758, 2002     

Solvatochromism in Binary Solvent Mixtures by Means of a Penta‐tert‐butyl Pyridinium N‐Phenolate Betaine Dye

The solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter, E_T (1) (kcal. mol^?1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye. For binary solvent mixtures, all plots of E_T (1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture. In the computation of E_T (1) it was assumed that the two solvents mixed interact to form a common structure with an E_T (1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents such as alcohols.     

Synthesis and solution properties of star‐shaped poly(tert‐butyl acrylate)

A series of star polymers consisting of poly(tert‐butyl acrylate) arms and an ethyleneglycol dimethacrylate (EGDMA) microgel core were synthesized using anionic polymerization. The effect of various parameters (precursor length, ratio [[EGDMA]/[Initiator], reaction time, and overall concentrations) on the average number of arms was investigated. Molecular weights were determined using GPC coupled with an online viscometer and MALLS. The exponents for the relation between intrinsic viscosity or radius of gyration and molecular weight, respectively, are extremely low, indicating that the dimensions of the star polymers only slightly increase with the number of arms. After a certain number of arms is reached the intrinsic viscosity even decreases with molecular weight. Computer simulations for star polymers were carried out where the radius of gyration was calculated as a function of the number of arms. The results are in good agreement with the experimental data.     

Kinetic study of 2‐propanol and benzyl alcohol oxidation by alkaline hexacyanoferrate(III) catalyzed by a terpyridyl ruthenium complex

The complex (Trpy)RuCl₃ (Trpy = 2,2′:6′,2″‐terpyridine) reacts with alkaline hexacyanoferrate(III) to form a terpyridyl ruthenium(IV)‐oxo complex that catalyzes the oxidation of 2‐propanol and benzyl alcohol by alkaline hexacyanoferrate(III). The reaction kinetics of this catalytic oxidation have been studied photometrically. The reaction rate shows a first‐order dependence on [RU(IV)], a zero‐order dependence on [hexacyanoferrate(III)], a fractional order in [substrate], and a fractional inverse order in [HO⁻]. The kinetic data suggest a reaction mechanism in which the catalytic species and its protonated form oxidize the uncoordinated alcohol in parallel slow steps. Isotope effects, substituent effects, and product studies suggest that both species oxidize alcohol through similar pericyclic processes. The reduced catalytic intermediates react rapidly with hexacyanoferrate(III) and hydroxide to reform the unprotonated catalytic species. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 760–770, 2000     

Compressed‐gas‐induced crystallization in tert‐butyl poly(ether ether ketone)

tert‐Butyl‐substituted poly(ether ether ketone) (tBuPEEK), which does not undergo crystallization with thermal annealing, crystallizes readily when treated with compressed CO₂. The dissolved CO₂ causes a reduction in the glass‐transition temperature of the polymer–gas system and enhances the chain mobility of the macromolecules, thereby bringing about crystallization. In the presence of CO₂, crystallization is increasingly favored with increasing CO₂ pressure and treatment temperature. The melting point of tBuPEEK crystals increases linearly with the CO₂ pressure applied in the treatment, indicating an increase in the order and/or size of the crystals. The extent of crystallinity increases when small amounts of methanol or dichloromethane are used as a cosolute with CO₂. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1505–1512, 2001