Kinetics of the reactions of tert-butanol with C2-C5 alcohols on sulfo cation exchangers

The kinetics of etherification of tert-butanol with aliphatic alcohols on gel KU-2×8 and macroporous KU-23 sulfo cation exchangers was studied. The first order of reaction with respect to tert-butanol and the -CSO₃H groups of a catalyst was established. The activation energy of the process observed on KU-2×8 was 60–95 kJ/mol. It was shown that the etherification of tert-butanol on KU-2×8 occurred in a surface layer. The reactivity of primary alcohols introduced into the reaction with tert-butanol increased with their molecular weights (C₂–C₅). The rate of reaction with secondary alcohols was lower than that with primary alcohols.     

Modeling of the θ(lower critical solution temperature) in polymer solutions using molecular connectivity indices

In this work, correlations for the estimation of the θ(lower critical solution temperature, LCST) for Polystyrene, Polyethylene, Polypropylene, Polybutene-1, Polypentene-1, Poly(4-methylpentene-1), Polydimethylsiloxane and Polyisobutylene solutions were proposed based on the molecular connectivity index. The correlations give satisfactory estimation of the θ(LCST), with the absolute error smaller than 20 K for most systems studied. Since the new correlations require only molecular connectivity indices of the solvent in the calculations, and the molecular connectivity indices can be calculated easily once the molecular structure of the substance concerned is known, they have better predictive capability and are easier to apply comparing with the existing methods and models.     

Conversion of tertiary alcohols to tert-alkyl azides by way of quinone-mediated oxidation-reduction condensation using alkyl diphenylphosphinites

A novel method for the preparation of alkyl azides from alcohols by way of oxidation-reduction condensation is described. In this reaction, the sterically-hindered tert-alkyl phosphinites that are prepared from the corresponding alcohols are converted into tert-alkyl azides with almost complete inversion of their stereochemistry: the obtained alkyl azides are then successfully reduced to afford the corresponding amines on treatment with LiAlH₄, thus, a versatile method for the preparation of chiral amines from the corresponding chiral alcohols is established.     

Efficient synthesis of carbonyl compounds: oxidation of azides and alcohols catalyzed by vanadium pentoxide in water using tert-butylhydroperoxide

Catalytic amount of vanadium reagent with tert-butylhydroperoxide as the oxidant was found to be an excellent oxidizing agent in aqueous medium. Vanadium pentoxide with aq tert-butylhydroperoxide readily oxidizes primary benzylic azides to the corresponding acids and secondary benzylic azides to the corresponding ketones in excellent yields. Further, vanadium pentoxide and aq tert-butylhydroperoxide combination turned out to be an effective catalyst for the oxidation of alcohols. Using vanadium pentoxide and aq tert-butylhydroperoxide primary alcohols were oxidized to the corresponding acids, whereas secondary alcohols underwent a smooth transformation to furnish corresponding ketones in excellent yields. All the oxidations are performed in water.     

The study of the relationship between the new topological index A(m) and the gas chromatographic retention indices of hydrocarbons by artificial neural networks

The newly developed topological indices A_m1-A_m3 and the molecular connectivity indices ^mX were applied to multivariate analysis in structure-property correlation studies. The topological indices calculated from the chemical structures of some hydrocarbons were used to represent the molecular structures. The prediction of the retention indices of the hydrocarbons on three different kinds of stationary phase in gas chromatography can be achieved applying artificial neural networks and multiple linear regression models. The results from the artificial neural networks approach were compared with those of multiple linear regression models. It is shown that the predictive ability of artificial neural networks is superior to that of multiple linear regression method under the experimental conditions in this paper. Both the topological indices ²X and A_m1 can improve the predicted results of the retention indices of the hydrocarbons on the stationary phase studied.     

Effect of alcohols on the gamma-radiation-induced polymerization of ethylene

Gamma-radiation-induced polymerization of ethylene in alcohols such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, and n-pentyl alcohols was carried out under a pressure of 400 kg./cm.²at 30°C. at a dose rate of 1.4 × 10⁵ rad/hr. in a batch reactor of 100 ml. capacity. The yield and molecular weight of polymer formed in the alcohols (except tert-butyl alcohol) were much lower than those of the bulk polymerization under the same conditions, whereas the addition of tert-butyl alcohol increased the yield and reduced the molecular weight. From the infrared spectra of the polymers and those of the bromination products it was concluded that only primary OH exists in the polymer formed in methyl alcohol and that both primary and secondary OH are in the polymer formed in other primary alcohols. Both secondary and tertiary OH were observed in the polymer when the secondary alcohols were used, and only tertiary OH in the case of tert-butyl alcohol. These polymers were found to contain small amounts of vinylidene unsaturation and methyl group. On the basis of these results the roles of the alcohols in the polymerization are discussed.     

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone

Nanofiltration membranes based on blend of polysulfone-g-poly(tert-butylacrylate) copolymer and polysulfone were prepared by phase inversion technique. ATRP grafting of tert-butylacrylate from chloromethylated polysulfone was used for the grafted polymer synthesis. The copolymer was characterized with FTIR, NMR, DSC and TGA. The prepared membranes were characterized in terms of pure water flux, water contact angle, cut off molecular weight, salt rejection and scanning electron microscopy.     

Modelling of the Critical Micelle Concentration of Cationic Gemini Surfactants Using Molecular Connectivity Indices

Modelling of the critical micelle concentrations (cmc) using the molecular connectivity indices was performed for a set of 21 cationic gemini surfactants with medium-length spacers. The obtained model contains only the second-order Kier and Hall molecular connectivity index. It is suggested that the index ² χ includes some information about flexibility. The obtained model was used to predict log₁₀ cmc of other cationic gemini surfactants. The agreement between calculated and experimental values of log₁₀ cmc for the gemini surfactants that were not used in the correlation is very good.     

Efficient transesterification of ethyl acetoacetate with higher alcohols without catalysts

The transesterification of ethyl acetoacetate (EtOAcac) without the use of catalysts is shown for primary, secondary and tertiary alcohols. The use of molecular sieves, which are used to shift the equilibrium, allows the synthesis of products in high yields and acceptable reaction times, which are on a par with those for transesterification processes using catalysts. The kinetics of the transesterification of EtOAcac with tert-amyl alcohol is studied.     

Chromato-mass-spectrometric identification of compounds with a branched carbon skeleton. Criteria for identifying tert-butyl groups in the structure of molecules

The previously proposed method of the integrated interpretation of mass-spectrometric and chromatographic data is applied to compounds with a branched carbon skeleton, namely, hydrocarbons containing tert-butyl groups. We estimate the increments of chromatographic retention indices for a hypothetical (CH₃)₃C → CH₃ transformation and determine the factors affecting their value. Several simple mass spectral characteristics are recommended to reveal tert-butyl groups in the structure of analyte molecules; however, one of the most informative criterion is to estimate the total number of carbon skeleton branches based on the homological increments of retention indices. The work shows high efficiency of the identification method proposed when the analytical and reference data are scarce.     

A direct functionalization of tertiary alkyl bromides with O-, N-, and C-nucleophiles

Silver oxide used in stoichiometric amounts promoted the direct functionalization of tert-alkyl bromides and provided the desired adducts in 39-96% isolated yield. Reaction of tert-bromides with carboxylic acids yielded esters, with alcohols and phenols yielded alkyl and aryl ethers, with amines and anilines yielded selectively mono-alkylated amines and anilines, and with a C-nucleophile yielded an all-carbon quaternary hydrocarbon. The method was applied to a sequential alkylation of a primary amine with two different alkyl bromides yielding selectively a tertiary amine with three different substituents in one-pot.     

Correlations between topological features and physicochemical properties of molecules

The article reviews in brief, thede novo group additivity approach and, at length, the different topological approaches to obtain predictive and internally consistent correlations between various properties and structural features of molecules. The stress has mainly been on the molecular connectivity method. A new rational scheme for nomenclature of connectivity indices of different orders and types is introduced. The concept of the perturbation connectivity parameter developed by us recently has been applied to obtain correlations for molar refraction, boiling point, molar volume, heat of atomisation, heat of combustion, heat of vaporisation, magnetic susceptibility and critical constants of alkanes, alcohols and alkylbenzenes. A comparative study of various approaches reveals that the present perturbation topological approach has an edge over other similar methods.     

Catalytic conversion of aliphatic alcohols on carbon nanomaterials: The roles of structure and surface functional groups

Carbon nanomaterials with the structure of graphene and different compositions of the surface groups are used as catalysts for the conversion of С₂–С₄ aliphatic alcohols. The conversions of ethanol, propanol- 1, propanol-2, butanol-1, butanol-2, and tert-butanol on carbon nanotubes, nanoflakes, and nanoflakes doped with nitrogen are investigated. Oxidized and nonoxidized multiwalled carbon nanotubes, nanoflakes, and nanoflakes doped with nitrogen are synthesized. X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning and transmission electronic microscopies, Brunauer–Emmett–Teller method, derivatographic analyses, and the pulsed microcatalytic method are used to characterize comprehensively the prepared catalysts. It was established that all of the investigated carbon nanomaterials (with the exception of nondoped carbon nanoflakes) are bifunctional catalysts for the conversion of aliphatic alcohols, and promote dehydration reactions with the formation of olefins and dehydrogenation reactions with the formation of aldehydes or ketones. Nanoflakes doped with nitrogen are inert with respect to secondary alcohols and tert-butanol. The role of oxygen-containing and nitrogen-containing surface groups, and of the geometrical structure of the carbon matrix of graphene nanocarbon materials in the catalytic conversion of aliphatic alcohols, is revealed. Characteristics of the conversion of aliphatic alcohols that are associated with their structure are identified.     

Solubility of ethyl-(2-hydroxyethyl)-dimethylammonium bromide in alcohols (C2–C12)

The solubilities of a novel third generation of the precursor of ionic liquids, named ethyl-(2-hydroxyethyl)-dimethylammonium bromide, C₂Br, in alcohols {ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol, 1-dodecanol, 2-butanol, 2-methyl-2-propanol (tert-butyl alcohol)} have been measured by a dynamic method from 240 to 440 K.The solubility of ethyl-(2-hydroxyethyl)-dimethylammonium bromide in primary alcohols decreases with an increase of the molecular weight of the alcohol from C₂ to C₁₂. The differences in solubilities between the primary and secondary alcohols are not significant. The solubility of C₂Br in tert-butyl alcohol is much lower than in 1-butanol and 2-butanol.The data were correlated by means of the UNIQUAC ASM, NRTL1 and NRTL2 equations, utilizing parameters derived from the (solid + liquid) equilibrium (SLE) data. The root-mean-square deviations of the solubility temperatures for all calculated data are from 2.36 to 7.17 K and depend on the particular equation used. In the calculations, the existence of a solid–solid first-order phase transition in pure C₂Br has also been taken into account.     

N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide

N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4 Å at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.