Selective dimerization of diisobutylene by oxo acids: Synthesis of isobutylene tetramer

Isobutylene tetramers (IB₄) were obtained in high yield by the cationic dimerization of commercial diisobutylene (DIB) (2,4,4-trimethyl-1-pentene with isomeric impurities) with CF₃SO₃O₃H or CH₃COClO₄ as catalyst. The best IB₄ yields (80–90%) were achieved at 0–30°C in nonpolar solvents (n-hexane and CCl₄). The major components in the IB₄ produced under these conditions were 2,2,6,6,8,8-hexamethyl-4-methylenenonane (8) and 2,2,4,6,6,8,8-heptamethyl-4-nonene (9) that arose via simple linear dimerization of DIB. The yield of IB₄ was almost independent of the monomer concentration ranging from 10 to 50 vol % at 0°C, but decreased at higher temperatures (>50°C) or in a polar solvent [(CH₂Cl)₂] because of the formation of higher oligomers and side reactions such as cracking. A Lewis acid catalyst (AlEtCl₂) resulted in a very complex mixture of C₁₂–C₂₀ hydrocarbons at 0°C in CCl₄; the yield of IB₄ was less than 40%. The catalytic difference between oxo acids and metal halides is discussed.     

Equilibrium of the simultaneous etherification of isobutene and isoamylenes with ethanol in liquid-phase

The simultaneous etherification of isobutene and isoamylenes with ethanol has been studied using macroreticular acid ion-exchange resins as catalyst. Most of the experiments were carried out over Amberlyst-35. In addition, Amberlyst-15 and Purolite CT-275 were also tested. Chemical equilibrium of four chemical reactions was studied: ethyl tert-butyl ether formation, tert-amyl ethyl ether formation from isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) and isomerization reaction between both isoamylenes. Equilibrium data were obtained in a batchwise stirred tank reactor operated at 2.0 MPa and within the temperature range from 323 to 353 K. Experimental molar standard enthalpy and entropy changes of reaction were determined for each reaction. From these data, the molar enthalpy change of formation of ethyl tert-butyl ether and tert-amyl ethyl ether were estimated. Besides, the chemical equilibrium between both diisobutene dimers, 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, was evaluated. A good agreement between thermodynamic results for the simultaneous etherification carried out in this work and those obtained for the isolated ethyl tert-butyl ether and tert-amyl ethyl ether systems was obtained.     

Übergangsmetalloxid- und Übergangsmetallacetylacetonat-katalysierte Olefinoxidation – ein Vergleich

Transition Metal Oxide- and Transition Metal Acetylacetonate-Catalyzed Olefine Oxidations – a Comparison The efficiencies of various homogeneous soluble transition metal acetylacetonates and of various heterogeneous transition metal oxides were studied to increase epoxide yields in autoxidation of olefins in liquid phase. The oxidation of cyclohexene, 1-octene, cis-4-octene, 3-ethyl-1-pentene and 2,4,4-trimethyl-1-pentene was investigated in absence of catalysts and in the presence of MoO₂(acac)₂ and MoO₃ as well as other oxides and heterogenized oxide-catalysts. The comparison of oxide- and acetylacetonate-catalysis gave a high similarity of both. MoO₃ acts preferentially as homogeneous catalyst too. Although other elements of heterogeneous catalysis were proved.     

Effects of methyl substitution in 4-silathiane S-oxides on the stereochemistry and 1 J CH coupling constants: Buttressing effect of axial sulfinyl group as the origin of the reverse Perlin effect

An NMR study of the products of lithiation/methylation of 4,4-dimethyl-4-silathiane S-oxide 1, diastereomers of 2,4,4-trimethyl-4-silathiane S-oxide 2 and 2,4,4,6-tetramethyl-4-silathiane S-oxide 3, as well as 4,4-dimethyl-4-silathiane S,S-dioxide 4 and 2,4,4-trimethyl-4-silathiane S,S-dioxide 5 is reported. The 2-Me group in 2,4,4-trimethyl-4-silathiane S-oxides is always equatorial while the SO group may occupy either the equatorial (major isomer, 2ee) or axial (minor isomer, 2ae) position. 2,4,4,6-Tetramethyl-4-silathiane S-oxide exists in the form of the two isomers, the one with 2-Me, 6-Me and sulfinyl groups all equatorial (3eee), and the other one as an equilibrium mixture of the axial and equatorial sulfoxides with 2-Me axial and 6-Me equatorial (3aae ?s 3eae). The normal Perlin effect (J _CHax?<?J _CHeq) is found for the CH₂ groups in all studied compounds except for the 3- and 5-CH₂ groups in 2ae and 5, which show a small reverse Perlin effect (J _CHax?>?J _CHeq). The experimental findings are interpreted in terms of the σ (C?Hax)?→?σ* (S?O) stereoelectronic effect for the C?H bonds in the 2- and 6-positions, and the buttressing effect of the axial SO group on the C?Hax bonds in the 3- and 5-positions and confirmed by GIAO-B3LYP/6-311G(d,p) theoretical calculations.     

Electrolytes for methanol-air fuel cells. 11. The electro-oxidation of methanol in trifluoromethane-sulphonic acid monohydrate and aqueous solutions of trifluoromethane-sulphonic acid

Trifluoromethanesulphonic acid monohydrate CF₃SO₃H.H₂O and its aqueous solutions have been evaluated as an electrolyte for methanol electro-oxidation. The performances of conventional noble metal catalysts in the pure monohydrate are very poor compared with those in 3 M sulphuric acid. This is contrary to previously published literature data, and possible reasons for the discrepancy are given. In aqueous solutions of CF₃SO₃H at concentrations between 10 and 50%wt. considerably improved performance is obtained and at 60° C the activities of the catalysts are in most cases slightly higher than in 3 M H₂SO₄. In addition the poisoning effect of acid radicals is considerably less in CF₃SO₃H than in H₂SO₄ solutions. Above 60° C, however, the aqueous CF₃SO₃ anion decomposes to produce sulphur, which poisons the noble metal catalysts.Carbon-13 NMR studies of the CF₃SO₃H/H₂O/CH₃OH system were carried out at 20 and 37° C. From the results it was concluded that no significant ester formation occurred between CH₃OH and CF₃SO₃H.H₂O at these temperatures. Earlier published data on¹H NMR studies of these solutions had indicated that 100% of the methanol was involved in ester formation with the acid. A critical analysis of this¹H NMR work is given.Cyclic voltammetric characterization of catalysts in 10 and 25%wt. aqueous CF₃SO₃H solutions gave similar results to those in 3 M H₂SO₄; however, at concentrations of 50% wt. the acid decomposed at 0.0 V to produce a sulphur species that poisoned the catalyst.The conclusion of the work was that while aqueous CF₃SO₃H solutions produced promising catalyst performance up to 60° C the slight improvement in performance over 3 M H₂SO₄ would not offset the greater expense of the CF₃SO₃H. In addition, it was suspected that the long-term stability of the aqueous solutions even at 60° C might be poor.     

Simple introduction of anion trapping site to polymer electrolytes through dehydrocoupling or hydroboration reaction using 9-borabicyclo[3.3.1]nonane

Organoboron-based anion trapping polymer electrolytes were synthesized through hydroboration or dehydrocoupling reaction between poly(propylene oxide) (PPO) oligomer (M_n = 400, 1200, 2000 and 4000) and 9-borabicyclo[3.3.1]nonane (9-BBN). Obtained oligomers were added various lithium salts (LiN(CF₃SO₂)₂, LiSO₃CF₃, LiCO₂CF₃ or LiBr) to analyze the ionic conductivity and lithium ion transference number (tLi⁺). The ionic conductivity of the oligomer in the presence of LiN(CF₃SO₂)₂ showed higher ionic conductivity than other systems, however, the tLi⁺ was less than 0.3. When LiSO₃CF₃ or LiCO₂CF₃, was added high tLi⁺ over 0.6 was obtained. Such difference in tLi⁺ can be explained by HSAB principle. Since boron is a hard acid, soft (CF₃SO₂)₂N⁻ anion can not be trapped effectively. High ionic conductivity of 1.3 × 10⁻⁶ S cm⁻¹ and high tLi⁺ of 0.73 was obtained when PPO chain length was 2000. These values of facilely prepared polymer electrolytes are comparable to those of the PPOs having covalently bonded salt moieties on the chain ends.     

The oxidation of isobutene to p-xylene over bismuth oxide-based catalysts

Studies have been carried out of the optimisation of a bismuth oxide based catalyst for the oxidation of isobutene to p-xylene. Using a Bi₂O₃-P₂O₅ (Bi:P = 2) catalyst located sequentially before a 3% Pt/Al₂O₃ catalyst, up to 60% selectivity can be observed at 50% conversion. The kinetics of the oxidation of isobutene over the Bi₂O₃-P₂O₅ catalyst have been measured for all major products. The results support a mechanism involving allylic oxidation of isobutene. Dimethylhexadiene and p-xylene are suggested to originate from reaction between two adsorbed isobutene molecules and monatomic oxygen species adsorbed at different sites. A major side product, methacrolein, appears to originate from reaction between two adsorbed isobutene molecules and a diatomic oxygen species.     

Butadiene polymerisation using ternary neodymium-based catalyst systems

Summary Ternary catalyst systems for the polymerisation of 1,3-butadiene to high cis content were studied. The systems Nd(carboxylate)₃/tert-butyl chloride/diisobutylaluminium hydride (carboxylate = naphthenate, versatate) were studied with respect to the order of catalyst component addition on catalyst activity and polymer characteristics. Stable catalysts which give relatively narrow molecular weight distribution are give by component addition order Nd(carboxylate)₃+diisobutylaluminium hydride+tert-butyl chloride. Less stable systems giving broader polymer molecular weight distributions are given by addition orders tert-butyl chloride+diisobutylaluminium hydride+Nd(carboxylate)₃ and Nd(carboxylate)₃ +tert-butyl chloride+diisobutylaluminium hydride.     

Ionic Liquid, 1‐n‐Butyl‐3‐methylimidazolium Bis(trifluoromethanesulfonyl)imide,Resulted in the First Catalyst‐Free Aminohalogenation of Electron‐Deficient Alkenes

The 2‐Ns‐based aminohalogenation of α,β‐unsaturated ketones has been achieved in an ionic liquid, 1‐n‐butyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide {[bmim][N(SO₂CF₃)₂]}. [Bmim][N(SO₂CF₃)₂] was found to be superior not only to classical organic solvents but also to its counterpart, [bmim][BF₄], which was proven to be successful in the TsNCl₂‐based aminohalogenation but failed to give any product for this reaction. The present process takes the advantage of 2‐NsNCl₂ as the stable nitrogen/halogen source in a one‐pot operation without the use of any metal catalysts, it is convenient to perform without special protection of inert gases. Eight examples were examined with good to excellent stereoselectivity (1:5 to one isomer) and modest to good chemical yields (53–72 %).     

New oxidation products of 2,2,5,7,8-pentamethyl-6-chromanol

Oxidation of the α-tocopherol model compound 2,2,5,7,8-pentamethyl-6-chromanol (1) byt-butyl hydroperoxide in chloroform, to which an alcohol has been added, produces 5-alkoxymethyl-2,2,7,8-tetramethyl-6-chromanol as the major product. In the present study,1 was oxidized byt-butyl hydroperoxide in water-saturated chloroform to determine whether water would influence product formation in the same way as alcohols. In addition to the usual products of oxidation such as 2-(3-hydroxy-3-methylbutyl)-3,5,6-trimethyl-1,4-benzoquinone (9), 5-formyl-2,2,7,8-tetramethyl-6-chromanol (11), the spirodimer and spirotrimer of1, three new products have been identified−2,2,7,8-tetramethyl-5-(2,2,5,7,8-pentamethyl-6-chromanoxy)methyl-6-chromanol (4), 5-hydroxymethyl-2,2,7,8-tetramethyl-6-chromanol (5) and 3-hydroxymethyl-2-(3-hydroxy-3-methylbutyl)-5,6-dimethyl-1,4-benzoquinone (7).     

Separability of SO2 from SO2/N2 mixture through sulfoxide-modified poly(vinyl alcohol) and cellulose membranes

Separability of SO₂ from mixtures of SO₂ and N₂ gases was studied for membranes of poly(vinyl alcohol) (PVA) and cellulose modified with methyl, ethyl, t-butyl, and phenyl vinyl sulfoxides. Of these sulfoxide-modified polymers, the phenyl vinyl sulfoxide-modified PVA membranes were found to give the best separation of SO₂. In the phenyl vinyl sulfoxide modified PVA membranes, the permeability coefficient of SO₂ increased with sulfoxide content while separability of SO₂ was maximum at a sulfoxide content of 23.5 mol %; the separation factor of SO₂ was about 170 at this sulfoxide content. © 1993 John Wiley & Sons, Inc.     

Nonvolatilealpha-branched chain fatty esters. II

A group of nonvolatilealpha-branched esters was prepared by the di-tertiary butyl peroxide-promoted addition of normal esters to terminal olefins containing methyl branches or aryl groups. Methyl stearate was added to 3,7-dimethyl-1-octene, 3,5,5-trimethyl-1-hexene, and 4-phenyl-1-butene. The reaction with 2,4,4-trimethyl-1-pentene, a terminal alkene with a methyl branch at the internal ethylenic carbon, was not successful. Benzyl 2-(4-phenylbutyl) octadecanoate was prepared by transesterification of the corresponding methyl ester. Benzyl 2,2-dimethylpropanoate, which has no α-hydrogen in the acyl portion of the molecule, was added to 1-hexadecene to form α-hexadecylbenzyl 2,2-dimethylpropanoate. Lubricant evaluation data were obtained on the above compounds. Presented at the AOCS Meeting, New Orlenas, May 1967. E. Utiliz. Res. Dev. Div., ARS, USDA.     

A recommended esterification method for gas chromatographic measurement of conjugated linoleic acid

The effect of the methylation method on isomerization of conjugated linoleic acid (CLA) in gas chromatographic analysis was studied. Among methylation methods examined, the magnitude of isomerization of CLA was greatest with BF₃ catalyst, followed by HCI and H₂SO₄ catalyst. Short-time methylation did not extensively change the CLA composition in all methods, and c,t and t,c isomers were essentially maintained, while the appearance of t,t isomers and unknown peaks was practically restricted. After 120 min of methylation, there was essentially no conversion in the H₂SO₄ method, in contrast to a marked change in the BF₃ method. The antioxidants butylated hydroxytoluene, ascorbic acid, β-carotene, and α-tocopherol did not suppress conversion, while dimethylsulfoxide (DMSO) and dimethylformamide (DMF) attenuated the changes in CLA composition. Suppression was more effective in the H₂SO₄ method than in the BF₃ method. Thus, methylation with H₂SO₄ in the presence of a proper amount of DMSO or DMF is recommended for esterification of CLA.     

Efficient dimerization of propylene affording 2,3-dimethylbutenes by fluorinated alcohol modified nickel-phosphine catalyst system containing strong sulfonic acid and/or dialkyl sulfates

A remarkable increase of both catalytic activity and the selectivity of dimers has been found for propylene dimerization affording 2,3-dimethylbutenes by a nickel-phosphine catalyst system composed of nickel naphthenate/P(cyclo-C₆H₁₁)₃/A lEt₃/ (CF₃)₂CHOH in the presence of CF₃SO₃H and/or Me₂SO₄: a combination of these effective additives also enhanced the reaction rates. This revised version was published online in July 2006 with corrections to the Cover Date.     

The effect of quaternary ammonium on discharge characteristic of a non-aqueous electrolyte Li/O2 battery

The effect of quaternary ammonium on discharge characteristic of Li/O₂ cells was studied by using Super-P carbon as air cathode, a 0.2 mol kg⁻¹ LiSO₃CF₃ 1:3 (wt.) PC/DME solution as baseline electrolyte, and tetrabutylammonium triflate (NBu₄SO₃CF₃) as an electrolyte additive or a co-salt. Results show that Li/O₂ cells can run normally in an electrolyte with NBu₄SO₃CF₃ as the sole conductive salt. However, such cells suffer lower voltage and capacity as compared with those using the lithium ionic baseline electrolyte. This is due to the larger molar volume of quaternary ammonium cation, which results in less deposition of oxygen reduction products on the surface of carbon. When used as an electrolyte additive or a co-salt, the ammonium is shown to increase capacity of Li/O₂ cells. The plot of differential capacity versus cell voltage shows that the Li/O₂ cell with ammonium added has broad and scatted differential capacity peaks between the voltages of two reactions of “2Li + O₂ → Li₂O₂” and “2Li + Li₂O₂ → 2Li₂O”. This phenomenon can be attributed to the phase transfer catalysis (PTC) property of quaternary ammonium on the second reaction. Due to inverse effects of the cation geometric volume and the PTC property of ammonium ions on the discharge capacity, there is an optimum range for the concentration of ammonium. It is shown that the addition of NBu₄SO₃CF₃ increases discharge capacity of Li/O₂ cell only when its concentration is in a range from 5 mol% to 50 mol% vs. the total of Li/ammonium mixed salt, and that the optimum concentration is about 5 mol%. In this work we show that the addition of 5 mol% NBu₄SO₃CF₃ into the baseline electrolyte can increase discharge capacity of a Li/O₂ cell from 732 mAh g⁻¹ to 1068 mAh g⁻¹ (in reference to the weight of Super-P carbon) when the cell is discharged at 0.2 mA cm⁻².     

Heteropolyacid-catalyzed dimerization of α-methylstyrene; on the efficiency and selectivity dependence

In the presence of catalytic amounts of a Keggin (H₃PW₁₂O₄₀), Wells–Dawson (H₆P₂W₁₈O₆₂) or Preyssler (H₁₄NaP₅W₃₀O₁₁₀) heteropolyacid, α-methylstyrene (1) leads to dimers. The efficiency and the selectivity toward 2,4-diphenyl-4-methyl-1-pentene (2), 2,4-diphenyl-4-methyl-2-pentene (3) and 1,1,3-trimethyl-3-phenylindan (4) depend on the reaction temperature and the nature of both the catalyst and the solvent. Thus, 2, 3 and 4 can be produced in 45%, 50% and 97% yields, respectively.     

Catalytic rearrangement of an aliphatic hydroperoxide

Metal triflates such as Sn(Otf)₂ and La(Otf)₃ act as efficient catalysts for cleaving 2,4,4,-trimethyl-pentane-2-hydroperoxide into neopentyl alcohol and acetone in sulpholane. Compared to H₂SO₄, the conventional catalyst for hydroperoxide rearrangement, the metal triflates achieve higher turnover numbers because they are less sensitive towards poisoning by the reaction product.     

Catalytic conversions in water. Part 5: Carbonylation of 1-(4-isobutylphenyl)ethanol to ibuprofen catalysed by water-soluble palladium–phosphine complexes in a two-phase system

1-(4-Isobutylphenyl)ethanol (IBPE) was carbonylated to 2-(4-isobutylphenyl)propionic acid (ibuprofen) in an aqueous/organic two phase system using the water-soluble Pd(tppts)₃ catalyst [tppts = P(C₆H₄-m-SO₃Na)₃] in the presence of p-CH₃C₆H₄SO₃H at 363 K, 15 MPa CO pressure and a palladium concentration of 150 ppm without addition of organic solvents. Under these conditions the conversion of IBPE was 83% and the selectivity to ibuprofen 82% with no decomposition of the Pd(tppts)₃ catalyst. Both the activity and selectivity were strongly influenced by the tppts/Pd molar ratio and the nature of the added Brønsted acid. Maximum efficiency was observed for P/Pd = 10. Acids of weakly or non-coordinating anions, such as p-CH₃C₆H₄SO₃H, CF₃COOH or HPF₆ afforded carbonylation. No catalytic activity was observed in the presence of acids of strongly coordinating anions, such as HI. The water-soluble Pd/dppps catalyst [dppps = Ar_2-nPh_nP-(CH₂)₃-PPh_n′Ar_2-n′; Ar = C₆H₄-m-SO₃Na; n = nń = 0: 86% and n = 0, nń = 1: 14%] exhibited low catalytic activity and the major product obtained was the linear isomer of ibuprofen, 3-(4-isobutylphenyl)propionic acid (3-IPPA) with selectivities up to 78%. Replacement of tppts by a ligand containing less −SO₃Na groups such as monosulphonated triphenylphosphine (tppms) gives rise to a dramatic drop in the catalytic activity and selectivity to ibuprofen. No catalytic activity was observed using palladium catalysts modified with 2-pyridyldiphenylphosphine (PyPPh₂) and tris(2-pyridyl)phosphine (PPy₃) which are both water soluble in their protonated form. A catalytic cycle is proposed to explain the observed results. ©1997 SCI     

Stereospecific synthesis of ditactic polymers

Summary Polymerizations of t-butyl crotonate (E-TBC) and t-butyl isocrotonate (Z-TBC) were carried out in toluene at-78°C using t-BuMgBr as initiator. E-TBC gave polymers, whereas Z-TBC did not. The dimer of E-TBC isolated from the polymerization mixture by means of GPC contained predominatly one of the four possible diastereomers. X-ray crystallographic determination showed that the predominant dimer was the erythro-diisotactic isomer. t-BuLi/Et₃Al polymerized effectively both E-TBC and Z-TBC in toluene. The poly(E-TBC)s prepared with t-BuMgBr and t-BuLi/Et₃Al were insoluble in toluene, THF, and chloroform, but soluble in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Stereostructure of the poly(TBC)s was analyzed by the one- and two-dimensional NMR spectra measured in HFIP. The poly(E-TBC) prepared with t-BuMgBr was a 1:1 mixture of the erythro- and threo-diisotactic polymers with high stereoregularity. The poly(E-TBC) and poly(Z-TBC) obtained from the polymerizations with t-BuLi/Et₃Al were rich in disyndiotactic structure. Polymerization of TBCs with t-BuLi in toluene and THF was also studied.

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Surface-tension properties of some polydispersed alkyl-substituted polyoxyethylated phenylsulfonamides

Twenty-nine laboratory-prepared polydisperse nonionic surfactants, derived from polyoxyethylatedN-alkylphenylsulfonamides [RϕSO₂ N(R′) (EO)_nH], have been characterized. EO is ethyoxylation;R is hydrogen,n-butyl ort-butyl;R′ is hexyl, octyl, or decyl; and (EO)_n is varied from (EO)₄ to (EO)₂₀. Surface tension in aqueous solution was studied. The critical micelle concentration, surface excess, minimum area per molecule, effectiveness of surface-tension reduction, and free energy of micelle formation were calculated from the surface-tension measurements. The critical micelle concentrations for the derivatives in whichR′-hexyl were considerably higher than the corresponding derivatives whereR′ is octyl or decyl. The greatest surface-tension reduction was found in theR′=n-octyl derivatives whereR ist-butyl with (EO)₉ orn-butyl with (EO)₁₁. Deceased.