CuCN catalyzed one pot synthesis of γ-keto diesters: domino double Michael addition followed by Nef reaction

An efficient one pot synthesis of γ-keto diesters through double Michael addition coupled with Nef reaction in the presence of CuCN catalyst and Cs₂CO₃ base is described. The reaction proceeds rapidly in DCM to give the products in good yields. A plausible mechanism is proposed.     

Formation and characterization of self-organized TiO2 nanotube arrays by pulse anodization

This paper describes TiO2 nanotube arrays prepared by anodic oxidation of Ti substrates using pulse voltage waveforms. Voltages were pulsed between 20 and -4 V or between 20 and 0 V with varying durations from 2 to 16 s at the lower limit of the pulse waveform. Ammonium fluoride or sodium fluoride (and mixtures of both) was used as the electrolyte with or without added medium modifier (glycerol, ethylene glycol, or poly (ethylene glycol) (PEG 400)) in these experiments. The pulse waveform was optimized to electrochemically grow TiO2 nanotubes and chemically etch their walls during its cathodic current flow regime. The resultant TiO2 nanotube arrays showed a higher quality of nanotube array morphology and photoresponse than samples grown via the conventional continuous anodization method. Films grown with a 20 V/-4 V pulse sequence and pulse duration of 2 s at its negative voltage limit afforded a superior photoresponse compared to other pulse durations. Specifically, the negative voltage limit of the pulse (-4 V) and its duration promote the adsorption of NH4+ species that in turn inhibits chemical attack of the growing oxide nanoarchitecture by the electrolyte F- species. The longer the period of the pulse at the negative voltage limit, the thicker the nanotube walls and the shorter the nanotube length. At variance, with 0 V as the low voltage limit, the longer the pulse duration, the thinner the oxide nanotube wall, suggesting that chemical attack by fluoride ions is not counterbalanced by NH3/NH4+ species adsorption, unlike the interfacial situation prevailing at -4 V. Finally, the results from this study provide useful evidence in support of existing mechanistic models for anodic growth and self-assembly of oxide nanotube arrays on the parent metal surface.     

Effects of Alkaline Ferrocyanide on Non-faradaic Yields of Anodic Contact Glow Discharge Electrolysis: Determination of the Primary Yield of OH· Radicals

Non faradaic yields of anodic contact glow discharge electrolysis (CGDE) originate through H^· and OH^· radical generated during the process. Scavenging effects of Fe(CN) ₆ ^4? on OH^· radicals, in alkaline media have been investigated. A kinetic analysis of the competing reactions of O^? with different species in the system leads to an yield of 9.8?mol?mol?electron^?1 of OH^· and H^· radicals each in the liquid phase reaction zone of anodic CGDE in good agreement with the yield reported from a study involving H^· radical scavengers.     

Sonolytic enhancement of the bactericidal activity of irradiated titanium dioxide suspensions in water

Irradiated TiO₂ suspensions in water were used to inactivate Escherichia coli and Hansenula polymorpha. Two types of batch reactors employing static and recirculating solutions were used in this study. Sonolysis using a 20 kHz ultrasonic unit was found to enhance the microorganism inactivation in all instances, although the enhancement was more modest for the batch recirculation reactor. These data are interpreted within the framework of four possible mechanisms. The mechanism based on sonolytic creation of ·OH appears to provide the most satisfactory explanation of the data trends. The present data also implicate ·OH as the dominant bactericidal agent in irradiated TiO₂ suspensions.