Partition layer-modified substrates for reversible surface-enhanced Raman scattering detection of polycyclic aromatic hydrocarbons

Herein, we present progress towards an analytical sensor for polycyclic aromatic hydrocarbons (PAHs) using surface-enhanced Raman scattering (SERS) on partition layer-modified nanostructured substrates. Specifically, a 1-decanethiol monolayer has been assembled on a silver film over nanospheres substrate to concentrate PAHs within the zone of SERS detection. Both anthracene and pyrene were detected with limits of detection at 300 and 700 pM, respectively. The measured SERS spectra allowed for easy distinction of the two PAH compounds, due to varying peak locations, and insight into the partitioning mechanism. Additionally, exposure to a common environmental interferant, Suwannee River fulvic acid, did not impede the measurement of the PAHs, and the sensor is reusable after a short exposure to 1-octanol. Finally, the utility of this sensing platform for PAH detection was compared to that achievable for other classes of organic pollutants such as polychlorinated biphenyls and polybrominated diphenyl ethers. Figure SERS detection of polycyclic aromatic hydrocarbons facilitated via partition layer modified substrates.

Mitsunobu Reactions Catalytic in Phosphine and a Fully Catalytic System

The Mitsunobu reaction is renowned for its mild reaction conditions and broad substrate tolerance, but has limited utility in process chemistry and industrial applications due to poor atom economy and the generation of stoichiometric phosphine oxide and hydrazine by‐products that complicate purification. A catalytic Mitsunobu reaction using innocuous reagents to recycle these by‐products would overcome both of these shortcomings. Herein we report a protocol that is catalytic in phosphine (1‐phenylphospholane) employing phenylsilane to recycle the catalyst. Integration of this phosphine catalytic cycle with Taniguchi’s azocarboxylate catalytic system provided the first fully catalytic Mitsunobu reaction.     

Generalizations of a result of Christensen on renewal sequences and linear recurrences

This note extends some recent work of Christensen on simple closed form solutions for linear recurrences, employing connections with renewal sequences. We obtain results for linear recursive sequences defined via monotone coefficients, and provide a broader result in the third-order case. A related open question is posed.     

Laser flash photolysis study of methanol addition to the C60 radical cation

Stable alcohol adducts of buckminsterfullerene (C₆₀) can be created via addition to C₆₀ radical cations. The radical cations were generated by photosensitized electron transfer from C₆₀ in a solution of N-methylacridinium hexafluorophosphate and biphenyl. Growth and decay of the C₆₀ radical cation population was monitored by transient absorption spectroscopy at 980 nm. The lifetime of the transient decreases in the presence of methanol, supporting trapping of the radical cation.     

A single Cu(II) catalyst for the three-component coupling of diverse nitrogen sources with aldehydes and alkynes

A single Cu(II) catalyst without the addition of ligand or base couples a diverse range of nitrogen sources with alkynes and aldehydes bearing alkyl, halogenated, silyl, aryl, and heteroaryl groups. The first example of a copper-catalyzed alkynylation involving p-toluenesulfonamide provides high yields of N-Ts-protected propargylamines. The superior activity of copper(II) triflate also allows this three-component alkynylation to incorporate a ketone.     

Slope and Line of Best Fit: A Transfer of Knowledge Case Study

This paper brings together research on slope from mathematics education and research on line of best fit from statistics education by considering what knowledge of slope students transfer to a novel task involving determining the placement of an informal line of best fit. This study focuses on two students who transitioned from placing inaccurate to accurate lines of best fit during a task‐based interview. The analysis focuses on describing shifts in slope reasoning that accompanied the change to accurately placed lines, and investigates factors that may have influenced the shift in reasoning. The results have implications for the teaching of both slope and the line of best fit.     

Glyco- and peptidomimetics from three-component Joullié-Ugi coupling show selective antiviral activity

Chlorination-elimination chemistry coupled with three-component Joullié-Ugi reaction and facile deprotection allowed efficient access to an array of polyhydroxylated pyrrolidines through parallel synthesis that may be considered to be a library of imino (aza) sugars (glycomimetics) and/or dihydroxyprolyl peptides (peptidomimetics). The utility of generating such a library was illustrated by screening against 15 different targets that revealed potent and selective inhibition of the Gaucher's disease glycosyltransferase enzyme glucosylceramide synthase and of primary pathogen model for human hepatitis C virus (HCV) and bovine diarrhoeal virus (BVDV). An observed selectivity for this HCV model over hepatitis B virus and remarkably low toxicity suggest a novel mode of action.