Abstract  Hydroperoxides are formed in significant amounts in the atmosphere by oxidation of volatile organic compounds and are key in aerosol formation. In a room-temperature experiment, we detected the formation of bimolecular complexes of tert-butyl hydroperoxide (t-BuOOH) and the corresponding alcohol tert-butanol (t-BuOH), with dimethyl ether (DME) as the hydrogen-bond acceptor. Using a combination of Fourier-transform infrared spectroscopy and quantum chemical calculations, we compare the strength of the OH-O hydrogen bond and the total strength of complexation. We find that, both in terms of observed red shifts and determined equilibrium constants, t-BuOOH is a significantly better hydrogen-bond donor than t-BuOH, a result that is backed by a number of calculated parameters and can be explained by a weaker OH bond in the hydroperoxide. On the basis of combined experimental and theoretical results, we find that the hydroperoxide complex is stabilized by ∼4 kJ/mol (Gibbs free energy) more than the alcohol complex. Measured red shifts show the same trend in hydrogen-bond strength with trimethylamine (N acceptor atom) and dimethyl sulfide (S acceptor atom) as the hydrogen-bond acceptors.

Abstract  FTIR spectroscopy of supersonic expansions is used to characterize alcohol dimers with one, two, and several nitrogen molecules attached to them. The nitrogen coating causes progressive spectral downshifts of the OH stretching fundamentals which are related to and explain matrix isolation shifts. Comparison of methanol, tert-butyl alcohol and ethanol as well as deuteration of methanol assist in the assignment. Alcohol monomers and trimers are significantly more resistant to nitrogen coating due to a lack of cooperativity and dangling bonds, respectively. In the case of ethanol, the role of conformational isomerism and combination bands is further elucidated. The experimental findings help rationalize the anomalously small OH stretching dimerization shift of methanol in the gas phase, in comparison to that of tert-butyl alcohol.

Abstract  The thermal and photochemical mechanistic pathways for tertiary alcohols on the rutile TiO2(110)-surface are studied with the example of tert-butanol. While the thermal reaction is known to yield isobutene, the photochemical ejection of a methyl radical is observed at 100 K. The C-C scission, which is accompanied by the formation of acetone, is the only photochemical reaction pathway at this temperature and can be attributed to the reaction of photoholes that are created upon UV-light illumination at the surface of the n-type semiconductor. At 293 K the selectivity of the reaction changes, as isobutene is additionally formed photochemically. A comparison of the kinetics of the different reactions reveals further insights. Together with the quantitative evaluation of the reaction products at low temperatures and the comparison of the reaction pathways at different temperatures it is demonstrated how thermal effects can influence the selectivity of the reactions in photocatalysis.

Abstract  Rate constants for the direct reactions of ozone with 45 potential organic drinking water contaminants, including solvents, haloalkanes, esters, aromatics and pesticides (such as alachlor, aldicarb, atrazine, carbofuran, 2,4-dichlorophenoxyacetic acid, endrin, glyphosate, etc.), have been measured in water in the presence of hydroxyl radical scavengers to minimize interfering radical chain reactions. The data demonstrate, again, the electrophilic nature of the ozonation reaction. In addition, for complex molecules, steric factors are important in limiting reactivity. The zwitterionic compound glyphosate exhibits a complex pH dependence that is explained by the inductive effect of side-chain protonation on the basicity of the amine reaction center. Rate constants for ozone consumption differ from those for compound consumption by an amount presumably equal to the reaction stoichiometry.

Abstract  Quantitative information regarding the length and stability condition of groundwater plumes of benzene, methyl tert-butyl ether (MTBE), and tert-butyl alcohol (TBA) has been compiled from thousands of underground storage tank (UST) sites in the United States where gasoline fuel releases have occurred. This paper presents a review and summary of 13 published scientific surveys, of which 10 address benzene and/or MTBE plumes only, and 3 address benzene, MTBE, and TBA plumes. These data show the observed lengths of benzene and MTBE plumes to be relatively consistent among various regions and hydrogeologic settings, with median lengths at a delineation limit of 10 µg/L falling into relatively narrow ranges from 101 to 185 feet for benzene and 110 to 178 feet for MTBE. The observed statistical distributions of MTBE and benzene plumes show the two plume types to be of comparable lengths, with 90th percentile MTBE plume lengths moderately exceeding benzene plume lengths by 16% at a 10-µg/L delineation limit (400 feet vs. 345 feet) and 25% at a 5-µg/L delineation limit (530 feet vs. 425 feet). Stability analyses for benzene and MTBE plumes found 94 and 93% of these plumes, respectively, to be in a nonexpanding condition, and over 91% of individual monitoring wells to exhibit nonincreasing concentration trends. Three published studies addressing TBA found TBA plumes to be of comparable length to MTBE and benzene plumes, with 86% of wells in one study showing nonincreasing concentration trends.

Abstract  A green technology of biodiesel production focuses on the use of enzymes as the catalyst. In enzymatic biodiesel synthesis, suitable solvent system is very essential to reduce the inhibition effects of the solvent to the enzymes. This study produced ethanol-based biodiesel from a low-cost sludge palm oil (SPO) using locally-produced Candida cylindracea lipase from fermentation of palm oil mill effluent (POME) based medium. The optimum levels of ethanol-to-SPO molar ratio and enzyme loading were found to be 4:1 and 10 U/25 g of SPO respectively with 54.4% w/w SPO yield of biodiesel and 21.7% conversion of free fatty acid (FFA) into biodiesel. Addition of tert-butanol at 2:1 tert-butanol-to-SPO molar ratio into the ethanol-solvent system increased the yield of biodiesel to 71.6% w/w SPO and conversion of FFA into biodiesel to 28.8%. The SPO and ethanol have promising potential for the production of renewable biodiesel using enzymatic-catalyzed esterification and transesterification.

Abstract  Butanol (C4H9OH) is a potential biofuel alternative in fossil fuel gasoline and diesel formulations. The usage of butanol would necessarily lead to direct emissions into the atmosphere; thus, an understanding of its atmospheric processing and environmental impact is desired. Reaction with the OH radical is expected to be the predominant atmospheric removal process for the four aliphatic isomers of butanol. In this work, rate coefficients, k, for the gas-phase reaction of the n-, i-, s-, and t-butanol isomers with the OH radical were measured under pseudo-first-order conditions in OH using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to monitor its temporal profile. Rate coefficients were measured over the temperature range 221-381 K at total pressures between 50 and 200 Torr (He). The reactions exhibited non-Arrhenius behavior over this temperature range and no dependence on total pressure with k(296 K) values of (9.68 ± 0.75), (9.72 ± 0.72), (8.88 ± 0.69), and (1.04 ± 0.08) (in units of 10(-12) cm(3) molecule(-1) s(-1)) for n-, i-, s-, and t-butanol, respectively. The quoted uncertainties are at the 2σ level and include estimated systematic errors. The observed non-Arrhenius behavior is interpreted here to result from a competition between the available H-atom abstraction reactive sites, which have different activation energies and pre-exponential factors. The present results are compared with results from previous kinetic studies, structure-activity relationships (SARs), and theoretical calculations and the discrepancies are discussed. Results from this work were combined with available high temperature (1200-1800 K) rate coefficient data and room temperature reaction end-product yields, where available, to derive a self-consistent site-specific set of reaction rate coefficients of the form AT(n) exp(-E/RT) for use in atmospheric and combustion chemistry modeling.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. RRM LITERATURE REVIEW RAT DIGESTIVE SYSTEM TOXICOLOGY HEPATOTOXICITY ALIPHATIC ALCOHOLS HALOGENATED HYDROCARBONS CARBON TETRACHLORIDE TOXICITY DIGESTIVE SYSTEM DISEASE

Abstract  Neat methanol and tert-butanol are studied by molecular dynamics with the focus on the microstructure of these two alcohols. The site-site radial distribution functions, the corresponding structure factors, and an effective local one-body density function are shown to be the appropriate statistical quantities that point in a complementary manner towards the same microstructure for any given liquid. Methanol is found to be a weakly associated liquid forming various chainlike patterns (open and closed) while tert-butanol is almost entirely associated and forms micellelike primary pattern. The presence of stable local microheterogeneity within homogeneous disordered phase appears as a striking feature of these liquids. The absence of any such apparent clustering in water--a stronger hydrogen bonding liquid--through the same two statistical quantities is analyzed.

Abstract  The molecular mobility of solid deuterated tert-butyl alcohol (TBA) has been studied over a broad temperature range (103–283 K) by means of solid-state 2H NMR spectroscopy, including both line shape and anisotropy of spin–lattice relaxation analyses. It has been found that, while the hydroxyl group of the TBA molecule is immobile on the 2H NMR time scale (τC > 10(–5) s), its butyl group is highly mobile. The mobility is represented by the rotation of the methyl [CD3] groups about their 3-fold axes (C3 rotational axis) and the rotation of the entire butyl [(CD3)3-C] fragment about its 3-fold axis (C3′ rotational axis). Numerical simulations of spectra line shapes reveal that the methyl groups and the butyl fragment exhibit three-site jump rotations about their symmetry axes C3 and C3′ in the temperature range of 103–133 K, with the activation energies and preexponential factors E1 = 21 ± 2 kJ/mol, k(01) = (2.6 ± 0.5) × 10(12) s(–1) and E2 = 16 ± 2 kJ/mol, k(02) = (1 ± 0.2) × 10(12) s(–1), respectively. Analysis of the anisotropy of spin–lattice relaxation has demonstrated that the reorientation mechanism of the butyl fragment changes to a free diffusion rotational mechanism above 173 K, while the rotational mechanism of the methyl groups remains the same. The values of the activation barriers for both rotations at T > 173 K have the values, which are similar to those at 103–133 K. This indicates that the interaction potential defining these motions remains unchanged. The obtained data demonstrate that the detailed analysis of both line shape and anisotropy of spin–lattice relaxation represents a powerful tool to follow the evolution of the molecular reorientation mechanisms in organic solids.

Abstract  The reaction of N,N'-dibenzyl-2-amino-4-imino-pent-2-ene, nacnac(Bn)H, with 1 or 2 equiv. of MgnBu₂ afforded the homoleptic complex nacnac(Bn)₂Mg. The reaction of nacnac(Bn)H with Mg(N(SiMe₃)₂)₂ yielded nacnac(Bn)MgN(SiMe₃)₂, which reacted with tert-butanol to form nacnac(Bn)MgOtBu. The latter complex crystallizes as an alkoxide bridge dimer and is active in the ring-opening polymerisation of rac-lactide. Polymerisations at room temperature afforded atactic polylactide, while polymerisations at -17 and -26 °C afforded polylactide with a small isotactic bias (P(m) = 0.52, and 0.55, respectively).

Abstract  PURPOSE: Variable-Temperature Kinetics has been used to obtain the rate constants of the reaction at various temperatures during one kinetic run.

METHODS: Pseudo-first-order rate constants for the transesterification of procaine with aliphatic alcohols ethanol, n-propanol and tert-butanol were obtained by the fluorescence spectroscopy using the variable-temperature kinetics (VTK) method.

RESULTS: The activation parameters of the reactions were calculated (24-28 kcal x mol(-1)). The half-life of the procaine decreases in the ethanol solution compared with the other alcoholic solutions in the presence of sodium ethoxide.

CONCLUSIONS: The investigation time of the reactions is reduced to one-tenth of the one used for usual kinetic methods.

Abstract  In the photochemical reactions of triplets of both protoporphyrin-IX-dimethyl-ester (PP) and haematoporphyrin dihydrochloride (HP) with alpha-phenyl-ethyl hydroperoxide (HROOH) in C6H6 at room temperature, both O-O and C-C bonds are broken yielding alkoxy and carbon-centred radicals. The ruptures of C-C and O-H bonds were observed in the photochemical reaction of PP with tert-butanol in the same solvent, yielding alkoxy and carbon-centred radicals at lambda greater than or equal to 366 nm, while HP did not react photochemically with tert-butanol at lambda greater than or equal to 334 nm.

Abstract  The explosive properties of mixtures of aqueous hydrogen peroxide (H(2)O(2)) and different alcohols (R-OH) like 2-propanol (2-PropOH), 2-methyl-2-propanol (TBA), 2-methyl-2-butanol (TAA) and 2-methyl-2-pentanol (THA) were investigated. Among others, the potential hazard of such mixtures may be characterized by their ability to react by different mechanisms of an explosion in the condensed phase, e.g. the thermal explosion or the detonation. Accordingly, the mixtures were experimentally investigated either by heating them up under confinement in different autoclaves or by exposing them to a shock wave impact applying the steel tube test. The results are discussed and compared to literature data.

Abstract  Recent neutron scattering experiments on aqueous salt solutions of amphiphilic t-butanol by Bowron and Finney [Phys. Rev. Lett. 89, 215508 (2002); J. Chem. Phys. 118, 8357 (2003)] suggest the formation of t-butanol pairs, bridged by a chloride ion via O-H...Cl- hydrogen bonds, leading to a reduced number of intermolecular hydrophobic butanol-butanol contacts. Here we present a joint experimental/theoretical study on the same system, using a combination of molecular dynamics (MD) simulations and nuclear magnetic relaxation measurements. Both MD simulation and experiment clearly support the more classical scenario of an enhanced number of hydrophobic contacts in the presence of salt, as it would be expected for purely hydrophobic solutes. [T. Ghosh et al., J. Phys. Chem. B 107, 612 (2003)]. Although our conclusions arrive at a structurally completely distinct scenario, the molecular dynamics simulation results are within the experimental error bars of the Bowron and Finney data.

Abstract  The threshold of reversible capillary condensation is a well-defined thermodynamic property, as evidenced by corresponding states treatment of literature and experimental data on the lowest closure point of the hysteresis loop in capillary condensation-evaporation cycles for several adsorbates. The nonhysteretical filling of small mesopores presents the properties of a first-order phase transition, confirming that the limit of condensation reversibility does not coincide with the pore critical point. The enthalpy of reversible capillary condensation can be calculated by a Clausius-Clapeyron approach and is consistently larger than the condensation heat in unconfined conditions. Calorimetric data on the capillary condensation of tert-butyl alcohol in MCM-41 silica confirm a 20% increase of condensation heat in small mesopores. This enthalpic advantage makes easier the overcoming of the adhesion forces by the capillary forces and justifies the disappearing of the hysteresis loop.

Abstract  The purpose of this work was to investigate the phase behavior of tertiary butanol (TBA) and volatile ammonium salts in frozen mixtures with some commonly used excipients and the efficacy of such volatile additives in accelerating the sublimation of ice from frozen solutions. Differential scanning calorimetry was employed to determine first-order phase transformations and glass transition temperatures in binary and ternary mixtures. Ice sublimation rates were studied by conventional freeze-drying and mass loss with time. A eutectic temperature (268 K) was identified for the anhydrous TBA-sucrose system. In frozen ternary water-excipient-TBA systems, the relative amplitudes of the glass and phase transitions, as measured during warming scans, were found to depend critically on the previous cooling rates. Glass transitions of all the freeze-concentrated mixtures used were determined. The sublimation studies indicated an ability of all volatile additives to accelerate ice sublimation from amorphous, freeze-concentrated solutions, but no clear ranking order, applicable to all systems studied, could be established.

Abstract  Utilizing differential scanning calorimetry (DSC) for tertiary butyl alcohol (TBA) solutions a phase diagram was constructed for the TBA-water system. By utilizing thermal treatment during the DSC measurements the metastable states were eliminated. The phase diagram fit that for a congruently melting compound in which compound formation occurred with a maximum at 70% TBA representing pure TBA hydrate. Two eutectics occurred at 20% (Eutectic A) and 90% (Eutectic B). A freeze-drying microscope revealed that TBA altered the crystal habit of ice. A concentration of 3% TBA was required before large needle-shaped ice crystals became evident. The addition of 10% TBA to the system resulted in even finer needle-shaped ice crystals. At the eutectic compositions (20% and 90% TBA), the frozen eutectic mixture could not be resolved with the microscope because eutectic crystals are very small. The 70% TBA solution, which corresponds to the melting of pure TBA hydrate, formed very large hydrate crystals. The rate of sublimation of the TBA and water molecules was found to be concentration dependent. At concentrations below 20% TBA (water rich portion of the phase diagram) water molecules sublimed faster while at concentrations above 20% TBA (TBA rich portion of the phase diagram) TBA molecules sublimed faster. At the eutectic A composition, both TBA and water molecules sublimed at the same rate. This may be because all of the TBA molecules are strongly associated with each other in the form of a clathrate hydrate.

Abstract  In this work, the interaction of different isomers of lower aliphatic alcohols with LDL representing a complex macromolecular assembly is investigated in vitro. Emphasis is given to the comparison of the impact of molecular architecture of methanol, ethanol, propanol (n-, iso-) and butanol (n-, iso-, sec-, tert-) in perturbing the lipid-protein assembly. The geometrical characteristics as well as the lipophilicity of the respective alcohol are considered. The EPR method combined with the spin labeling of both the apoB and the lipid monolayer allowed parallel detection of changes provoked in both phases. In addition to the change in protein environment, the spectral decomposition of the experimental data revealed a decrease in lipid ordering with the increasing concentration of the alcohols. This phenomenon for aliphatic alcohols is linearly correlated with the equal volume occupation (EVO) of alcohol in LDL. The results support the molecular mechanism of alcohol action through its interference with the lipid-protein interactions in LDL, which could be applicable to the molecular mechanism of alcohol interaction with integral membrane proteins.

Abstract  Self-assembly of Zn(ClO4)2 with 1,1,2,2-tetramethyl-1,2-di(pyridin-3-yl)disilane (L) as a bidentate N-donor gives rise to 3D coordination networks, [Zn(μ-OH)(L)]3(ClO4)3·5H2O (1·5H2O), of unique, 103-a srs net topology. An important feature is that two enantiomeric 3D frameworks, 41- and 43-[Zn(μ-OH)(L)]3(ClO4)3·5H2O, are interpenetrated to form a racemic two-fold 3D network with cages occupied by two water molecules. Another structural characteristic is a C3-symmetric planar Zn3(μ-OH)3 6-membered ring with tetrahedral Zn(ii) ions. The steric hindrance of substrates and trace water effects on transesterification catalysis using the network have been scrutinized. The coordination network acts as a remarkable heterogeneous transesterification catalytic system that shows both the significant steric effects of substrate alcohols and momentous water effects. The substrate activity is in the order ethanol > n-propanol > n-butanol > iso-propanol > 2-butanol > tert-butanol. For the reaction system, solvate water molecules within the cages of the interpenetrated 3D frameworks do not decrease the transesterification activity, whereas the trace water molecules in the substrate alcohols act as obvious obstacles to the reaction.

Abstract  In the present contribution, the pre-structuring of binary mixtures of hydrotropes and H2O is linked to the solubilisation of poorly water miscible compounds. We have chosen a series of short-chain alcohols as hydrotropes and benzyl alcohol, limonene and a hydrophobic azo-dye (Disperse Red 13) as organic compounds to be dissolved. A very weak pre-structuring is found for ethanol/H2O and 2-propanol/H2O mixtures. Pre-structuring is most developed for binary 1-propanol/H2O and tert-butanol/H2O mixtures and supports the bicontinuity model of alcohol-rich and water-rich domains as already postulated by Anisimov et al. Such a pre-structuring leads to a high solubilisation power for poorly water miscible components (limonene and Disperse Red, characterized by high octanol/water partition coefficients, log(P) values of 4.5 and 4.85), whereas a very weak pre-structuring leads to a high solubilisation power for slightly water miscible components (benzyl alcohol). This difference in solubilisation power can be linked to (i) the formation of mesoscale structures in the cases of ethanol and 2-propanol and (ii) the extension of pre-structures in the cases of 1-propanol and tert-butanol. Three different solubilisation mechanisms could be identified: bulk solubilisation, interface solubilisation and a combination of both. These supramolecular structures in binary and ternary systems were investigated by small-and-wide-angle X-ray and neutron scattering, dynamic light scattering and conductivity measurements (in the presence of small amounts of salt).