Proton or Metal? The H/D Exchange of Arenes in Acidic Solvents

The H/D exchange of arenes in acidic media by transition-metal and main-group-metal complexes and common inorganic salts was studied. The influence of Lewis acidity, anions, charge, and ligands was evaluated. The results indicate that the determination of H/D exchange activity in acidic media is not related to the formation of metal–carbon bonds (i.e., C–H activation). The combined experimental data (regioselectivity, activation energy, kinetics, isotope effects, solvent effects) and DFT calculations point toward a proton catalysis mechanism. Thus, highly Lewis acidic metal compounds, such as aluminum(III) triflate, were extraordinarily active for the H/D exchange reactions. Indeed, the degree of H/D exchange reactivity allows for a comparative measurement of Lewis acidities

Thermochemical properties of different 1-(R-phenyl)-1H-imidazoles

© 2016 Elsevier B.V.Phenyl substituted imidazoles exhibit versatile biological activity. 1-(R-phenyl)-1H-imidazoles with different functional groups R provide a convenient suitcase of molecules with tunable physicochemical properties adjustable for many practical applications. In this work, the absolute vapor pressures of 1-(R-phenyl)-1H-imidazoles (with R = H, 2-methyl, 4-methyl, 2-methoxy, 4-methoxy, 2-fluoro, 4-fluoro, 2-bromo and 4-bromo) at different temperatures have been measured by the transpiration method for the first time. The standard enthalpies of vaporization of these compounds were derived from the temperature dependencies of the vapor pressures. An internal consistency of the standard vaporization enthalpies has been proven by comparison with vaporization enthalpies of parent species, as well as by a group contribution method. A system of group-additivity values is suggested for a quick assessment of vaporization enthalpies of different 1-(R-phenyl)-1H-imidazoles. Gas-phase standard molar enthalpies of formation of 1-(R-phenyl)-1H-imidazoles have been calculated using the high-level quantum-chemical method G3MP2. The combination of experimentally determined standard vaporization enthalpies with the G3MP2 results allows for the prediction of the liquid-phase standard enthalpies of formation for the studied compounds

Thermochemical Properties of Tunable Aryl Alkyl Ionic Liquids (TAAILs) based on Phenyl-1H-imidazoles

© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimVaporization enthalpies of five different imidazolium based Tunable Aryl Alkyl Ionic Liquids (TAAILs) with a common bis(trifluoromethylsulfonyl)imide ([NTf2]) anion were measured using a Quartz Crystalline Microbalance (QCM) and by Thermogravimetric Analysis (TGA). The counter anion and the alkyl chain of these imidazolium-based ionic liquids with one N-aryl and one N-alkyl substituent were kept constant to study the influence of the ortho- and para-substituted aryl moieties on the vaporization enthalpies of these ionic liquids. For comparison, enthalpies of vaporization measured at elevated temperatures were adjusted to the reference temperature 298 K. Structure-property relations between TAAILs and similarly shaped corresponding 1-(R-phenyl)-imidazoles were analyzed. An incremental approach to predict vaporization enthalpies of ionic liquids by group contributions was suggested. The procedure is based on vaporization enthalpy of a starting IL and group contributions well established from molecular compounds

Divergent Views of Hope Influencing Communications Between Parents and Hospital Providers

This study evaluates parents’ and health care providers’ (HCPs) descriptions of hope following counseling of parents at risk of delivering an extremely premature infant. Data came from a longitudinal multiple case study investigation that examined the decision-making and support needs of 40 families and their providers. Semi-structured interviews were conducted before and after delivery. Divergent viewpoints of hope were found between parents and many HCPs and were subsequently coded using content analysis. Parents relied on hope as an emotional motivator, whereas most HCPs described parents’ notions of hope as out of touch with reality. Parents perceived that such divergent beliefs about the role of hope negatively shaped communicative interactions and reduced trust with some of their providers. A deeper understanding of how varying views of hope might shape communications will uncover future research questions and lead to theory-based interventions aimed at improving the process of discussing difficult news with parents

Production of Single W Bosons at LEP

We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be $0.61^{+0.43}_{-0.33} \pm 0.05 \; \rm{pb}$ at the centre of mass energy \sqrt{s}=172 \GeV{}, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous $\gamma$WW gauge couplings are derived at 95\% CL: $\rm -3.6 \Delta \kappa_\gamma 1.5$ and $\rm -3.6 \lambda_\gamma 3.6$

RBAC Policies in XML for X.509 Based Privilege Management

This paper describes a role based access control policy template for use by privilege management infrastructures where the roles are stored as X.509 Attribute Certificates in an LDAP directory. There is a brief description of the X.509 privilege management model, and how it can be used to implement RBAC. Policies that conform to the template are written in XML, and the template is specified as a DTD. (A future version will specify it as an XML schema). The policy is designed to be used by the PERMIS API, a Java specification for an Access Control Decision Function based on the ISO 10181 Access Control Framework and the Open Group’s AZN API