Direct Access to Aryl Bis(trifluoromethyl)carbinols from Aryl Bromides or Fluorosulfates: Palladium‐Catalyzed Carbonylation

A palladium‐catalyzed carbonylative approach for the direct conversion of (hetero)aryl bromides into their α,α‐bis(trifluoromethyl)carbinols is described, and it employs only stoichiometric amounts of carbon monoxide and trifluoromethyltrimethylsilane. In addition, aryl fluorosulfates proved highly compatible with these reaction conditions. The method is tolerant of a diverse set of functional groups, and it is adaptable to late‐stage carbon‐isotope labeling.     

On the possible catalysis by single water molecules of gas-phase hydrogen abstraction reactions by OH radicals

The gas phase hydrogen abstraction reaction between OH and CY(2)XH, where X = H, F, OH, or NH(2) and Y = H, CH(3) or F, in the absence and presence of a single water molecule is investigated using both density function theory, B3LYP, and explicitly correlated coupled cluster theory, CCSD(T)-F12. We find that a single water molecule could have a catalytic effect at low temperatures possible in laboratory experiments, but does not seem to catalyze these reactions at 298 K, and will not play a role under relevant atmospheric conditions.     

Direct Access to Isotopically Labeled Aliphatic Ketones Mediated by Nickel(I) Activation

An extensive range of functionalized aliphatic ketones with good functional‐group tolerance has been prepared by a Ni^I‐promoted coupling of either primary or secondary alkyl iodides with NN₂ pincer Ni^II‐acyl complexes. The latter were easily accessed from the corresponding Ni^II‐alkyl complexes with stoichiometric CO. This Ni‐mediated carbonylative coupling is adaptable to late‐stage carbon isotope labeling, as illustrated by the preparation of isotopically labelled pharmaceuticals. Preliminary investigations suggest the intermediacy of carbon‐centered radicals.     

Multistate Switches: Ruthenium Alkynyl–Dihydroazulene/Vinylheptafulvene Conjugates

Multimode molecular switches incorporating distinct and independently addressable functional components have potential applications as advanced switches and logic gates for molecular electronics and memory storage devices. Herein, we describe the synthesis and characterization of four switches based on the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermoswitch pair functionalized with the ruthenium‐based Cp*(dppe)Ru ([Ru*]) metal complex (dppe=1,2‐bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl). The [Ru*]–DHA conjugates can potentially exist in six different states accessible by alternation between DHA/VHF, Ru^II/Ru^III, and alkynyl/vinylidene, which can be individually stimulated by using light/heat, oxidation/reduction, and acid/base. Access to the full range of states was found to be strongly dependent on the electronic communication between the metal center and the organic photoswitch in these [Ru*]–DHA conjugates. Detailed electrochemical, spectroscopic (UV/Vis, IR, NMR), and X‐ray crystallographic studies indeed reveal significant electronic interactions between the two moieties. When in direct conjugation, the ruthenium metal center was found to quench the photochemical ring‐opening of DHA, which in one case could be restored by protonation or oxidation, allowing conversion to the VHF state.     

An Application of Adaptive Independent Chain Metropolis–Hastings Algorithms in Bayesian Hazard Rate Estimation

In this paper, we consider adaptive independent chain (AIC) Metropolis–Hastings algorithms as introduced in a special context in Gåsemyr et al. (2001) and developed theoretically in Gåsemyr (2003). The algorithms aim at producing samples from a specific target distribution , and are adaptive, non-Markovian versions of the Metropolis–Hastings independent chain. A certain parametric class of possible proposal distributions is fixed, and the parameters of the proposal distribution are updated periodically on the basis of the recent history of the chain, thereby obtaining proposals that get ever closer to . In the former paper a version of these algorithms was shown to be very efficient compared to standard simulation techniques when applied to Bayesian inference in reliability models with at most three dependent parameters. The aim of the present paper is to investigate the performance of the AIC algorithm when the number of dependent parameters and the complexity of the model increases. As a test case we consider a model treated in Arjas and Gasbarra (1996). The target distribution is the posterior distribution for the vector X=(X ₁,...,X _n ) of dependent parameters, representing a piecewise constant approximation to the hazard rate X(t), where t ₀ t t _n . Especially, for the case n=12 it turned out that some versions of the AIC were very efficient compared to standard simulation techniques and also to the algorithm applied in Arjas and Gasbarra (1996). This includes a version of the componentwise adaptive independent chain the basic idea of which was given in Gåsemyr (2003).     

Gas-Phase Ion Fluorescence Spectroscopy of Tailor-made Rhodamine Homo- and Heterodyads: Quenching of Electronic Communication by π-Conjugated Linkers

While many key photophysical features are understood for electronic communication between chromophores in neutral compounds, there is limited information on the effect of charges in practically relevant ionic chromo/fluorophores. Here we have chosen positively charged rhodamines and prepared a selection of homo- and heterodimers with alkyl or π-conjugated, acetylenic bridges. Protonated molecules were transferred as isolated ions to gas phase where there is no solvent screening of charges, and fluorescence spectra were measured with a custom-made ion-trap setup. Our work reveals strong polarization of the π-spacer (induced dipole/quadrupole) when it experiences the electric field from one/ two dyes. Hence, π-spacers provide efficient shielding of charges by reducing the Coulomb interaction, whereas two dye cations polarize each other when connected by an alkyl. The screening influences the Förster resonance energy transfer efficiency that relies on the dipole–dipole interaction.     

Behavior and Stability of Naphthenic Acid/Naphthenate Stabilized Emulsions. Mixed C80-Tetraacid and Stearic Acid Stabilization

Previous studies have focused on monomeric naphthenic acids and their ability to stabilize emulsions, but little has been reported on C80-tetraacids and their ability to function as an emulsifier. In this article, we report on the chemistry of the C80-tetraacids as an emulsion stabilizer and also on the role this acid has in mixed monoacid-tetraacid systems. The study focuses on the type of emulsion formed and the stability of these emulsions with respect to water cut, pH, salinity of the water phase, and type of counterion. Interfacial behavior and the electrostatic properties of the emulsion were studied in order to determine which of the acids were present at the interface and which of the acids gave the largest contribution to the emulsion stability. It was found that C80-tetraacids form only O/W emulsion under the conditions studied. Addition of monoacid to the system did not change the type of emulsion formed. Highest stability was seen for emulsions containing both monoacid and tetraacids. When adding NaCl a phase inversion from O/W to W/O emulsion appeared around a concentration of 2 wt% of NaCl.     

SPE-HPLC purification of endocrine-disrupting compounds from human serum for assessment of xenoestrogenic activity

Assessment of xenoestrogenic activity in human serum samples requires the removal of endogenous sex hormones to assure that the activity measured originates from xenobiotic compounds only. Serum samples representing high, medium and lower accumulation of persistent organic pollutants (POPs) were extracted using solid-phase extraction (SPE) followed by normal-phase high-performance liquid chromatography (NP-HPLC) for separation of POPs from endogenous hormones. The recovery of polychlorinated biphenyl (PCB) congeners in spiked serum samples was up to 86 %, making the extraction method suitable for the study. MVLN cells, stably transfected with an estrogen receptor (ER) luciferase reporter vector (estrogen response element chemically activated luciferase expression, ERE-CALUX), were exposed to the reconstituted SPE-HPLC extracts for determination of the integrated estrogenic activity. The effects of PCBs were analyzed by direct in vitro exposure of PCBs (nos. 138, 153, 180) and by ex vivo analysis of SPE-HPLC extracts from serum spiked with the PCBs. Similar effects on ER transactivation were observed for the direct in vitro and the ex vivo analysis experiments. The ER transactivation responses determined for actual serum samples were in the linear range of the dose-response curve. 17β-Estradiol titrations showed that the xenoestrogenic effects were mediated via ER. Moreover, our SPE-HPLC-ERE-CALUX assay was demonstrated to elicit high interlaboratory correlation. In the present study the combination of SPE-HPLC purification and the ex vivo estrogenic responses measured by ERE-CALUX was validated and considered to be a valuable tool to assess the combined ER effect of lipophilic serum POPs where additive/synergistic and agonistic/antagonistic effects are integrated giving an overall estimate of exposure and bioactivity.