Triflic acid–catalyzed rearrangement of unalkylated benzene sulfonanilides

Previous work has demonstrated that alkylated benzene sulfonanilides undergo sulfuric acid (98%)–catalyzed rearrangement to alkylamino diaryl sulfones. Similar treatment of their unalkylated analogs typically leads only to hydrolysis. Surprisingly, when the unalkylated benzene sulfonanilides react with triflic acid, rearrangement to sulfones does occur.     

Electrocatalysis of oxygen reduction on multi-walled carbon nanotube supported copper and manganese phthalocyanines in alkaline media

Manganese phthalocyanine (MnPc) and copper phthalocyanine (CuPc)-modified electrodes were prepared using multi-walled carbon nanotubes (MWCNTs) as a support material. The catalyst materials were heat treated at four different temperatures to investigate the effect of pyrolysis on the oxygen reduction reaction (ORR) activity of these electrocatalysts. The MWCNT to metal phthalocyanine ratio was varied. Scanning electron microscopy (SEM) was employed to visualise the surface morphology of the electrodes and the x-ray photoelectron spectroscopic (XPS) study was carried out to analyse the surface composition of the most active catalyst materials. The ORR was studied in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. Glassy carbon (GC) electrodes were modified with carbon nanotube-supported metal phthalocyanine catalysts using Tokuyama AS-4 ionomer. The RDE results revealed that the highest electrocatalytic activity for ORR was achieved upon heat treatment at 800 °C. CuPc-derived catalyst demonstrated lower catalytic activity as compared to the MnPc-derived counterpart, which is in good agreement with previous literature, whereas the activity of MnPc-based catalyst was higher than that reported earlier.     

NMR spectroscopic investigation of inclusion complexes between cyclodextrins and the neurotoxin tetramethylenedisulfotetramine

The binding stoichiometry, strength and structure of inclusion complexes formed between the neurotoxin tetramethylenedisulfotetramine (TETS) and both native and modified cyclodextrins (CyDs) were investigated using nuclear magnetic resonance (NMR) spectroscopy. Of all six examined cases, native β‐cyclodextrin (β‐CyD) and its chemically modified counterpart heptakis‐(2,3,6‐tris‐(2‐hydroxypropyl))‐β‐cyclodextrin (2HP‐β‐CyD) were found to associate most strongly with TETS as reflected in the magnitude of their binding constants (K = 537 ± 26 M^?1 for β‐CyD and K = 514 ± 49 M^?1 for 2HP‐β‐CyD). Two‐dimensional rotating‐frame Overhauser effect spectroscopy NMR experiments confirm close proximity of the TETS molecule to both β‐CyD and 2HP‐β‐CyD as intermolecular, through‐space interactions between the H3 and H5 protons located in the interior of the CyD cavity and the methylene protons of TETS were identified. Copyright © 2012 John Wiley & Sons, Ltd.     

Grignard condensation routes to 1,3‐disilacyclobutane‐containing cyclolinear polycarbosilanes

Alkylene‐ and arylene‐bridged cyclolinear polycarbosilanes (CLPCS) with 1,3‐disilacyclobutane (DSCB) rings incorporated in the main chain of the polymer were prepared by polycondensation between corresponding di‐functional DSCB derivatives and di‐Grignard reagents. Well‐defined, low molecular weight (M_n = 3–5K; DP = 17–26), hexylene‐ and phenylene‐bridged CLPCS polymers were obtained without appreciable ring opening of the DSCB rings. Large exothermic peaks were observed in the DSC for these CLPCSs, which indicated, along with the IR spectra, that crosslinking occurred on heating to about 250 °C via the ring opening of the embedded, alternating, DSCB rings. Moreover, PB‐CLPCS undergoes photochemically induced crosslinking on UV irradiation to form crosslinked polycarbosilane network films. The spin‐cast, cured, films of these CLPCSs exhibit relatively low dielectric constants and promising thermal and mechanical properties for applications in electronics, for example, directly UV‐photoimprinted low‐k dielectrics. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1547–1557