Home  About us  Contact
 

CH2Cl2/alcohol Solvents (alcohol + solvent)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

The First General and Selective Palladium(II)-Catalyzed Alkoxycarbonylation of Arylboronates: Interplay among Benzoquinone-Ligated Palladium(0) Complex, Organoboron, and Alcohol Solvent

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Yoshihiko Yamamoto
Abstract Methoxycarbonylation of aryl- and alkenylboron compounds was performed using the palladium(II) acetate/triphenylphosphine [Pd(OAc)2/PPh3] catalyst with p -benzoquinone as a stoichiometric oxidant in methanol at ambient temperature to obtain the corresponding methyl esters in good yields. A wide variety of functional groups including various carbonyl functionalities, nitrile, nitro, sulfone, and unprotected pyrrole rings were tolerated in the methoxycarbonlation, while the use of higher alcohols except for tert -butanol afforded various p -chlorobenzoates in moderate to high yields. The catalytic alkoxycarbonylation proceeded without any acid or base additive, and an oxidative transmetalation step is proposed to explain the exceptional efficacy of this protocol. DFT and MP2 calculations support the proposed mechanism. [source]

Solvent Effects on Catalytic Epoxidation of Alkenes by Tetra- n -butylammonium Periodate and (Tetraarylporphyrinato)manganese(III)

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2008
Daryoush Mohajer
Abstract The epoxidation of cyclooctene and cis -stilbene was performed by tetra- n -butylammonium periodate (nBu4NIO4)in the presence of (tetraarylporphyrinato)manganese(III) [Mn(por)] and imidazole (im) in various CH2Cl2/alcohol solvents (alcohol = CH3OH, C2H5OH, n -C3H7OH, i -C3H7OH, t -C4H9OH). In accord with the coordinating abilities of the alcohols to [Mn(por)], the epoxidation yields increased from CH2Cl2/CH3OH to CH2Cl2/t -C4H9OH. In the epoxidation of cis -stilbene in the presence of (acetato)(tetraphenylporphyrinato)manganese(III) [Mn(tpp)(OAc)], the cis - to trans -stilbene oxide ratio increased consistently with the bulk of the alcohol in CH2Cl2/alcohol solvents. Also, it was found that the interaction of [Mn(tpp)(OAc)] and (acetato)(tetramesitylporphyrinato)manganese(III) [Mn(tmp)(OAc)] with nBu4NIO4 in the presence of imidazole but in the absence of alkenes yields [Mn(tpp)(O)(im)]+ and [Mn(tmp)(O)(im)]+ complexes. The formation of the Mn=O species for the small linear alcohols was faster than that for the larger ones, whereas the stability of the Mn=O complex was greater in the presence of the bulkier alcohols. Attempts were made to explain these effects.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Blind crystal structure prediction of a novel second polymorph of 1-hydroxy-7-azabenzotriazole

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2006
Harriott Nowell
The commercially available peptide coupling reagent 1-hydroxy-7-azabenzotriazole has been shown to crystallize in two polymorphic forms. The two polymorphs differ in their hydrogen-bonding motif, with form I having an (10) dimer motif and form II having a C(5) chain motif. The previously unreported form II was used as an informal blind test of computational crystal structure prediction for flexible molecules. The crystal structure of form II has been successfully predicted blind from lattice-energy minimization calculations following a series of searches using a large number of rigid conformers. The structure for form II was the third lowest in energy with form I found as the global minimum, with the energy calculated as the sum of the ab initio intramolecular energy penalty for conformational distortion and the intermolecular lattice energy which is calculated from a distributed multipole representation of the charge density. The predicted structure was sufficiently close to the experimental structure that it could be used as a starting model for crystal structure refinement. A subsequent limited polymorph screen failed to yield a third polymorphic form, but demonstrated that alcohol solvents are implicated in the formation of the form I dimer structure. [source]

Effect of Solvation Film on the Viscosity of Colloidal Dispersions

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2005
Peng Chang-Sheng
Abstract Viscosity is one of the most important properties of colloids in mixing, transportation, stabilization, energy consumption, and so on. According to Einstein's viscosity equation, the viscosity of a colloidal dispersion increases with the increase of particle concentration. And the equation can be applicable to all micro-particle dispersions, because the effect of solvation films coated on particles can be neglectable in that case. But with the decrease of particle size to nano-scale, the formation of solvation films on nano-particles can greatly affect the viscosity of a dispersion, and Einstein's equation may not be applicable to this case. In this work, one kind of micro-size silica particle and two kinds of nano-size silica particles were used to investigate the effect of solvation films on dispersion viscosity, dispersed in water and ethyl alcohol solvents, respectively. The results of theoretical calculation and experimental investigation show that the increase of viscosity is contributed from solvation films by more than 95 percent for nano-particle dispersions, while less than 10 percent for micro-particle dispersions. [source]