Peroxide initiated maleic anhydride grafting: Structural studies on an ester‐containing copolymer and related substrates

Maleic anhydride (MAn) was grafted onto the low molecular weight esters methyl decanoate (MD) and methyl 2‐ethylhexanoate (MEH) using the free‐radical initiators Lupersol‐101 and ‐130; the esters were used as model compounds for the copolymer poly(ethylene‐co‐methyl acrylate). The grafted products in both cases were isolated from the unreacted ester and were subjected to extensive analysis using spectroscopic and chromatographic techniques. Analysis of the grafted material indicated the presence of one or more succinic anhydride (SAn) residues grafted to the ester. In the case of the multiply grafted material it has been established conclusively by ¹³C‐NMR using 2,3‐¹³C₂ labeled MAn that the multiple grafts exist as single units. A limited number of grafting experiments was performed on the copolymer in the melt and the graft‐modified copolymer was characterized spectroscopically. Single graft units were observed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1609–1618, 1999     

A chiral rhodium complex for rapid asymmetric transfer hydrogenation of imines with high enantioselectivity

[formula: see text] A chiral rhodium complex, (R)-Cp*RhCl[(1S,2S)-p-TsNCH(C6H5)CH(C6H5)NH2] (1a, (S,S)-Cp*RhClTsDPEN), generated from [Cp*RhCl2]2 and (1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine [(S,S)-TsDPEN], and its enantiomer 1b were found to provide superior catalysts for the rapid, high-yielding, asymmetric transfer hydrogenation of some heterocyclic imines, using an HCO2H-Et3N azeotrope as the hydrogen source.     

Copper and zinc removal from aqueous solution by mixed mineral systems II. The role of solution composition and aging

This study investigates Cu and Zn removal onto binary mixed mineral sorbents from simulated wastewater, relevant to streams impacted by acid mine drainage and effluents. Mixed suspensions of kaolinite/montmorillonite and kaolinite/goethite exhibited different sorption behavior from the single mineral components, reducing Cu and Zn removal (except Cu sorbed on montmorillonite/goethite) over the range of pH investigated. Cu and Zn removal by the electrolyzed systems showed a complex response to increased ionic strength, which increased solid concentration, leading to lower Cu and Zn sorption. Enhanced Cu sorption on the montmorillonite/goethite as age increased may be attributed to increased hydroxylation of the mineral surface resulting in the formation of new reactive sites.     

Carbon dioxide emulsion assisted loading of polymer microspheres toward sustained release materials

An organic solvent-free method for encapsulating progesterone at high loadings within micron-sized inert latex polymer beads is reported. This approach makes use of a polymeric surfactant to emulsify carbon dioxide into an aqueous latex suspension. In this way, preformed approximately 4 microm polystyrene (PS) microparticles surface-grafted with poly(N-vinylpyrrolidone) (PVP) were plasticized and swollen followed by rapid partitioning of progesterone into the polymer matrix. The as-prepared polystyrene beads incorporated over 10% progesterone by weight while maintaining their initial size and morphological uniformity. Dissolution experiments were also carried out to obtain the release profile of progesterone entrapped within the PVP/PS particles.     

Enantioselective synthesis of axially chiral 1-(1-naphthyl)isoquinolines and 2-(1-naphthyl)pyridines through sulfoxide ligand coupling reactions

Racemic 1-(1′-isoquinolinyl)-2-naphthalenemethanol rac-12 was prepared through a ligand coupling reaction of racemic 1-(tert-butylsulfinyl)isoquinoline rac-7 with the 1-naphthyl Grignard reagent 10. Resolution of rac-12 was achieved through chromatographic separation of the Noe-lactol derivatives 14 and 15, providing (R)-(−)-12 of >99% ee and (S)-(+)-12 of 90% ee. The ligand coupling reaction of optically enriched sulfoxide (S)-(−)-7 (62% ee) with Grignard reagent 10 furnished rac-12, with the absence of stereoinduction resulting from competing rapid racemisation of the sulfoxide 7. Reaction of optically enriched (S)-(−)-7 with 2-methoxy-1-naphthylmagnesium bromide was also accompanied by racemisation of the sulfoxide 7, and furnished optically active (+)-1-(2′-methoxy-1′-naphthyl)isoquinoline (+)-3b in low enantiomeric purity (14% ee). The absolute configuration of (+)-3b was assigned as R using circular dichroism spectroscopy, correcting an earlier assignment based on the Bijvoet method, but in the absence of heavy atoms. Optically active 2-pyridyl sulfoxides were found not to undergo racemisation analogous to the 1-isoquinolinyl sulfoxide 7, with the ligand coupling reactions of (R)-(+)- and (S)-(−)-2-[(4′-methylphenyl)sulfinyl]-3-methylpyridines, (R)-(+)-17 and (S)-(−)-17, with 2-methoxy-1-naphthylmagnesium bromide providing (−)- and (+)-2-(2′-methoxy-1′-naphthyl)-3-methylpyridines, (−)-18 and (+)-18, in 53 and 60% ee, respectively. The free energy barriers to internal rotation in 3b and 18 have been determined, and the isoquinoline (R)-(−)-12 examined as a ligand in the enantioselectively catalysed addition of diethylzinc to benzaldehyde; (R)-(−)-12 was also converted to (R)-(−)-N,N-dimethyl-1-(1′-isoquinolinyl)-2-naphthalenemethanamine (R)-(−)-19, and this examined as a ligand in the enantioselective Pd-catalysed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate.     

Electron-capture gas chromatographic analysis of beta-phenylethylamine in tissues and body fluids using pentafluorobenzenesulfonyl chloride for derivatization

A gas chromatographic procedure is described for the analysis of beta-phenylethylamine (PEA) in tissues and body fluids. The method involves the use of pentafluorobenzenesulfonyl chloride for extraction and derivatization of PEA. This is followed by separation and analysis of the derivatized amine on a gas chromatograph equipped with a fused-silica capillary column and an electron-capture detector. The procedure is rapid, provides a stable and sensitive derivative, and has been applied to analysis of PEA in brain, heart, kidney, liver, lung, spleen and blood from the rat and urine from human subjects.     

The Impact of Research Culture on Mental Health & Diversity in STEM

The onset of COVID-19, coupled with the finer lens placed on systemic racial disparities within our society, has resulted in increased discussions around mental health. Despite this, mental health struggles in research are still often viewed as individual weaknesses and not the result of a larger dysfunctional research culture. Mental health interventions in the science, technology, engineering, and mathematics (STEM) academic community often focus on what individuals can do to improve their mental health instead of focusing on improving the research environment. In this paper, we present four aspects of research that may heavily impact mental health based on our experiences as research scientists: bullying and harassment; precarity of contracts; diversity, inclusion, and accessibility; and the competitive research landscape. Based on these aspects, we propose systemic changes that institutions must adopt to ensure their research culture is supportive and allows everyone to thrive.     

A Structures for Lossless Ion Manipulations (SLIM) Module for Collision Induced Dissociation

A collision induced dissociation (CID) structure for lossless ion manipulations (SLIM) module is introduced and coupled to a quadrupole time-of-flight (QTOF) mass spectrometer. The SLIM CID module was mounted after an ion mobility (IM) drift tube to enable IM/CID/MS studies. The efficiency of CID was studied by using the model peptide leucine enkephalin. CID efficiencies (62%) compared favorably with other beam-type CID methods. Additionally, the SLIM CID module was used to fragment a mixture of nine peptides after IM separation. This work also represents the first application of SLIM in the 0.3 to 0.5 Torr pressure regime, an order of magnitude lower in pressure than previously studied.

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The first aldehyde-derived crystalline geminal diol lacking internal electronic stabilization

The first stable crystalline geminal diol of an aldehyde lacking electron-withdrawing groups on the-carbon was synthesized fromd-sorbitol and characterized by¹H and¹³C nuclear magnetic resonance (NMR) and single-crystal x-ray studies. Each hydroxyl is a donor for a single, unique intermolecular hydrogen bond. Only one hydroxyl acts as an acceptor. No intramolecular hydrogen bonding is observed in the crystal.