Convenient Ring-Bromination of Alkylnaphthalenes using N-Bromosuccinimide in Acetonitrile

Abstract: Abstract. 1-Alkyl- and 2-alkylnaphthalenes are conveniently brominated in the 4-and 1-positions respectively using N-bromosuccinimide (NBS) in acetonitrile. The reactions are easy to perform and give higher chemical yields and better regioselectivity compared to brominations employing bromine/dichloromethane.     

Bipolar Electrochemistry

A bipolar electrode (BPE) is an electrically conductive material that promotes electrochemical reactions at its extremities (poles) even in the absence of a direct ohmic contact. More specifically, when sufficient voltage is applied to an electrolyte solution in which a BPE is immersed, the potential difference between the BPE and the solution drives oxidation and reduction reactions. Because no direct electrical connection is required to activate redox reactions, large arrays of electrodes can be controlled with just a single DC power supply or even a battery. The wireless aspect of BPEs also makes it possible to electrosynthesize and screen novel materials for a wide variety of applications. Finally, bipolar electrochemistry enables mobile electrodes, dubbed microswimmers, that are able to move freely in solution.     

Amidrazones 9. Convenient Syntheses of 1-Alkyl-1-Phenylhydrazines and α,β-Unsaturated Amidrazones Via Base-Promoted Reactions of 1,1-Disubstituted-3-Amino-4,5-Dihydro-1H-Pyrazolium Salts

A simple, efficient procedure for the conversion of phenylhydrazine to 1-alkyl-1-phenylhydrazines via base-promoted hydrolysis of 1-alkyl-3-amino-4,5-dihydro-1-phenyl-1H-pyrazolium iodides (2) is described. N¹, N¹-disubstituted hydrazones of trans-cinnamamide and acrylamide are obtained by Hofmann-type ring openings of 1,1 -disubstituted-3-amino-4,5-dihydro-5-phenyl (or 5-unsubstituted) -1H-pyrazolium halides (5, 7).     

Cholesteric liquid crystal displays as optical sensors of barbiturate binding

The influence on the optical properties of cholesteric liquid crystal displays (LCDs) was examined for neutral molecule binding by mesogen/receptors in the mesomorphic phase. The motivation was to prepare neutral molecule sensors that use a colour change to signal analyte binding. A receptor that binds barbiturate analytes was modified with two or one cholesteryl groups to yield compounds 2 and 3, respectively. LCDs were prepared by incorporating one of the receptor/mesogen compounds into a cholesteric LC blend along with a potential H‐bonding guest. The optical properties of the LCDs were then determined by measuring the absorbance of the displays. For various LCDs, the colour of the display depended upon several factors: the amount of guest molecule used, the number of cholesteryl side chains on the receptor and the mole concentration of receptor/mesogen in the blend. In particular, complementary host/guest binding of H‐bonding analytes by the bis(cholesteryl) receptor 2 in a cholesteric LCD caused a change of up to +70 nm, which was observed by the naked eye as a blue‐to‐orange colour change. Control experiments confirm that the colour of an LCD is a consequence of molecular recognition in the mesomorphic phase.