Structural aspects in the dielectric properties of pentyl alcohols

Acylative Dynamic Kinetic Resolution of Secondary Alcohols: Tandem Catalysis by HyperBTM and Bäckvall's Ruthenium Complex

Non-enzymatic dynamic kinetic resolution (DKR) of secondary alcohols by enantioselective acylation using an isothiourea-derived HyperBTM catalyst and racemization of slowly reacting alcohol by Bäckvall's ruthenium complex is reported. The DKR approach features high enantioselectivities (up to 99:1), employs easy-to-handle crystalline 4-nitrophenyl isobutyrate as the acylating reagent, and proceeds at room temperature and under an ambient atmosphere. The stereoinduction model featuring cation-π system interactions between the acylated HyperBTM catalyst and π electrons of an alcohol aryl subunit has been elaborated by DFT calculations.

Describing Temperature-Dependent Self-Diffusion Coefficients and Fluidity of 1- and 3-Alcohols with the Compensated Arrhenius Formalism

The location of the hydroxyl group in monohydroxy alcohols greatly affects the temperature dependence of the liquid structure due to hydrogen bonding. Temperature-dependent self-diffusion coefficients, fluidity (the inverse of viscosity), dielectric constant, and density have been measured for several 1-alcohols and 3-alcohols with varying alkyl chain lengths. The data are modeled using the compensated Arrhenius formalism (CAF). The CAF follows a modified transition state theory using an Arrhenius-like expression to describe the transport property, which consists of a Boltzmann factor containing an energy of activation, Ea, and an exponential prefactor containing the temperature-dependent solution dielectric constant, εs(T). Both 1- and 3-alcohols show the Ea of diffusion coefficients (approximately 43 kJ mol(-1)) is higher than the Ea of fluidity (approximately 35 kJ mol(-1)). The temperature dependence of the exponential prefactor in these associated liquids is explained using the dielectric constant and the Kirkwood-Frölich correlation factor, gk. It is argued that the dielectric constant must be used to account for the additional temperature dependence due to variations in the liquid structure (e.g., hydrogen bonding) for the CAF to accurately model the transport property.

Dynamics of glass-forming liquids. XVII. Dielectric relaxation and intermolecular association in a series of isomeric octyl alcohols

It is well established that many mono-hydroxy alcohols show an extra relaxation process of the Debye type in addition to the signatures of primary and secondary structural relaxations, which is observed only in dielectric spectroscopy and related techniques. In order to gain further insight into the nature of this Debye peak, we study the linear and nonlinear dielectric behavior of a series of isomeric octyl alcohols and of mixtures of n-propanol with one of the octanols. These samples display systematic variations of the Debye peak intensity and concomitant changes in the Kirkwood correlation factor gK from 0.1 to 4, indicative of different equilibrium constants, K(c∕r), that characterize the populations of non-polar ring and polar open chain structures. For cases where K(c∕r) is not too far from unity, we find that a high electric field shifts K(c∕r) towards more chains, and that the accompanying change in the end-to-end vector of hydrogen-bond connected structures occurs on the Debye time scale. The results suggest that gK is correlated with the spectral separation of the Debye and primary structural peaks, as both features depend on steric hindrance of chain flexibility or bond rotation barriers and on average chain lengths. Based on the complex dynamics of supercooled mono-hydroxy alcohols with three relaxation peaks that cover many orders of magnitude in frequency, it is argued that a frequency dependent gK may be required for assessing the average orientational correlations within hydrogen-bonded structures correctly.