Solvent Influence on Selectivity in α-Pinene Oxide Isomerization Using MoO3-Modified Zeolite BETA

Natural source turpentine is an available source of α-pinene oxide. This compound’s value is especially given by the possibility of producing important compounds campholenic aldehyde and trans-carveol. In this work, we would like to present the usage of MoO3-modified zeolite BETA in α-pinene oxide isomerization concerning campholenic aldehyde and trans-carveol formation using a wide range of solvents. Catalyst calcination temperature also influenced the reaction course (selectivity to desired compounds and reaction rate). MoO3-zeolite BETA was prepared by the wet impregnation method and characterized by different techniques. The use of polar aprotic solvents had the most positive effect on the reaction course. Solvent basicity and polarity considerably influenced the reaction rate and selectivity to particular products. The combination of high basicity and the high polarity was the most suitable for the studied reaction from the reaction rate point of view. Selectivity to campholenic aldehyde and trans-carveol was the most influenced by solvent basicity. Higher solvent basicity caused the preferential formation of trans–carveol, influence on selectivity to campholenic aldehyde formation was the opposite. The described catalyst may be used for α-pinene oxide rearrangement to both desired products dependently on the used solvent. Molybdenum offers an exciting alternative for previously described modifications of zeolites for this reaction.

Using computational chemistry to explore experimental solvent parameters – solvent basicity, acidity and polarity/polarizability

Solvent basicity and polarity/polarizability parameters are analysed using molecular properties of solvents derived from computational chemistry. The results show that Kamlet and Taft’s measure of hydrogen bond basicity, β, is essentially identical to Gutmann’s donor number, a measure of Lewis basicity, both being determined by the charge on the most negative atom of the solvent molecule and the energy of the electron donor orbital. It is also found that, for both parameters, the calculated values for alcohols and N–H containing bases deviate systematically from those for aprotic solvents. This mirrors Kamlet and Taft’s earlier observation that different solvatochromic probes yield different β values in amphiprotic solvents. Reichardt’s ET (30) and Kamlet, Abboud and Taft’s π* both show direct dependences on the dipole moments and quadrupolar amplitudes of the solvent molecules and, surprisingly, an inverse dependence on the molecular polarizability. Additionally, ET (30) has a strong dependence on the charge on the most positive hydrogen atom of the solvent molecule, reflecting its sensitivity to hydrogen bonding. Unexpectedly, π* shows a dependence on the energy of the electron donor orbital. Kammet and Taaft’s hydrogen bond acidity parameter, α, is discussed in light of the results for π* and ET (30).

Solvatochromism in urea/water and urea-derivative/water solutions

Solvent acidity (SA), solvent basicity (SB), and solvent dipolarity and polarizability (SPP) parameters for urea and water mixtures.

Solvent basicity controlled deformylation for the formation of furfural from glucose and fructose

Furfural was synthesized from hexose sugars instead of 5-HMF by using polar aprotic solvents with very low basicity.

Solvent basicity promotes the hydride-mediated electron transfer doping of carbon nanotubes

Donor solvents accelerate the hydride-mediated n-type doping of carbon nanotubes.