Micellar kinetics in aqueous acetonitrile. Part A. Sodium-hydrogen ion-exchange constant for 1-dodecanesulfonate surfactant. Part B. Substrate structural effects for micellar catalysis by perfluorooctanoic acid as reactive counterion surfactant

The sodium-hydrogen ion exchange constant for the system sodium 1-dodecanesulfonate-hydrochloric acid in aqueous acetonitrile has been determined from the pseudo-phase ion exchange model for surfactant catalytic effects. The results indicate that the micellar system behaves similarly for the aqueous and the aqueous acetonitrile (2.106 M) solvent systems. The influence of substrate molecular structure on micellar catalysis by perfluorooctanoic acid of the hydrolysis of hydroxamic acids (R—CO—NHOH) in aqueous acetonitrile has been explored. Data for substrate structures of fifteen compounds with R=alkyl, aralkyl, alicyclylalkyl, phenylalkyl, alkyl-substituted phenylalkyl, and with chain branching at the α, β, and γ positions are compared. Relative binding constant values indicate that substrates with aromatic groups are less well solubilized in the perfluoro micellar environment than are substrates with saturated groups. There is now evidence for specific micellar effects on the reaction rate as well as general micellar catalysis. © 1997 John Wiley & Sons, Inc.     

Non-oxidative Methane Coupling over Silica versus Silica-Supported Iron(II) Single Sites

Non-oxidative CH₄ coupling is promoted by silica with incorporated iron sites, but the role of these sites and their speciation under reaction conditions are poorly understood. Here, silica-supported iron(II) single sites, prepared via surface organometallic chemistry and stable at 1020 °C in vacuum, are shown to rapidly initiate CH₄ coupling at 1000 °C, leading to 15–22 % hydrocarbons selectivity at 3–4 % conversion. During this process, iron reduces and forms carburized iron(0) nanoparticles. This reactivity contrasts with what is observed for (iron-free) partially dehydroxylated silica, that readily converts methane, albeit with low hydrocarbon selectivity and after an induction period. This study supports that iron sites facilitate faster initiation of radical reactions and tame the surface reactivity.     

N-Heterocyclic Carbenes Reduce and Functionalize Copper Oxide Surfaces in One Pot

Benzimidazolium hydrogen carbonate salts have been shown to act as N-heterocyclic carbene precursors, which can remove oxide from copper oxide surfaces and functionalize the resulting metallic surfaces in a single pot. Both the surfaces and the etching products were fully characterized by spectroscopic methods. Analysis of surfaces before and after NHC treatment by X-ray photoelectron spectroscopy demonstrates the complete removal of copper(II) oxide. By using ¹³C-labelling, we determined that the products of this transformation include a cyclic urea, a ring-opened formamide and a bis-carbene copper(I) complex. These results illustrate the potential of NHCs to functionalize a much broader class of metals, including those prone to oxidation, greatly facilitating the preparation of NHC-based films on metals other than gold.     

Theoretical and experimental analysis of the antioxidant features of substituted phenol and aniline model compounds

Structural Chemistry - Although natural polyphenols have attracted extended attention as antioxidants, there is only limited information available on their structure-activity relationship (SAR). In...     

Dynamics of the nearly parametric pendulum

Dynamically stable periodic rotations of a driven pendulum provide a unique mechanism for generating a uniform rotation from bounded excitations. This paper studies the effects of a small ellipticity of the driving, perturbing the classical parametric pendulum. The first finding is that the region in the parameter plane of amplitude and frequency of excitation where rotations are possible increases with the ellipticity. Second, the resonance tongues, which are the most characteristic feature of the classical bifurcation scenario of a parametrically driven pendulum, merge into a single region of instability.     

Rerouting chlorambucil to mitochondria combats drug deactivation and resistance in cancer cells

The difficulty of accessing the mitochondrial matrix has limited the targeting of therapeutics to this organelle. Here, we report, to our knowledge, the first successful delivery of an active DNA alkylating agent--chlorambucil--to mitochondria, and describe unexpected features that result from rerouting this drug within the cell. Mitochondrial targeting of this agent dramatically potentiates its activity, and promotes apoptotic cell death in a variety of cancer cell lines and patient samples. This retention of activity is observed even in cells with resistance to chlorambucil or disabled apoptotic triggering.     

The Relationship of Teacher‐Facilitated,Inquiry‐Based Instruction to Student Higher‐Order Thinking

Commissions, studies, and reports continue to call for inquiry‐based learning approaches in science and math that challenge students to think critically and deeply. While working with a group of middle school science and math teachers, we conducted more than 100 classroom observations, assessing several attributes of inquiry‐based instruction. We sorted the observations into two groups based on whether students both explored underlying concepts before receiving explanations and contributed to the explanations. We found that in both math and science classrooms, when teachers had students both explore concepts before explanations and contribute to the explanations, a higher percent of time was spent on exploration and students were more frequently involved at a higher cognitive level. Further, we found a high positive correlation between the percent of time spent exploring concepts and the cognitive level of the students, and a negative correlation between the percent of time spent explaining concepts and the cognitive level. When we better understand how teachers who are successful in challenging students in higher‐order thinking spend their time relative to various components of inquiry‐based instruction, then we are better able to develop professional development experiences that help teachers transition to more desired instructional patterns.     

Synthesis and reactivity of 3-amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones: development of a novel kinase-focussed library

3-Amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones represent a potentially attractive heteroaromatic scaffold for drug-discovery chemistry. In particular, the arrangement of hydrogen bond donor and acceptor groups in the bicyclic core can fulfil the requirements for ATP competitive binding to kinase enzymes. Efficient and regioselective routes from simple starting materials to novel functionalised 3-amino-1H-pyrazolo[4,3-c]pyridin-4(5H)-ones and related 3-amino-2H-pyrazolo[4,3-c]pyridines were explored and adapted for parallel synthesis, resulting in a library of compounds suitable for screening against kinases and other cancer drug targets. Methods for substituent variation at five distinct positions around the bicyclic core were devised to generate sets of compounds containing two- or three-point diversity.