Elektrochemische Synthesen, XV. Eine verbesserte kathodische Erzeugung von Dichlorcarben

Abstract

Galvanostatische Reduktion von CCl4 und CHCl3 an Bleikathoden in CHCl3/Bu4NBr oder CH2Cl2/Bu4NBr bei ‐5°C ergibt in Gegenwart von 2‐Methyl‐2‐buten, 2,3‐Dimethyl‐2‐buten, Phenylethylen und 2‐Phenylpropen die entsprechenden 1,1‐Dichlorcyclopropan‐Derivate über das intermediär entstehende Dichlorcarben in bis zu 80 proz. Stromausbeute an isolierter Substanz (Tabelle 1).

Reductive Cleavage of Carbon Tetrachloride in a Polar Solvent. An Example of a Dissociative Electron Transfer with Significant Attractive Interaction between the Caged Product Fragments

“…The first irreversible wave (which remains irreversible over the whole explored range of scan rates, i.e., up to 100 V/s) is a two-electron wave. The second, irreversible wave corresponds to the reduction of chloroform formed at the first wave, as checked with an authentic sample . We may infer from these data that the reduction at the first wave follows the mechanism depicted in Scheme .…”

“…The second, irreversible wave corresponds to the reduction of chloroform formed at the first wave, as checked with an authentic sample . We may infer from these data that the reduction at the first wave follows the mechanism depicted in Scheme . The second electron transfer is expected to take place at a potential much more positive than the first, which thus appears as the rate-determining step of the whole reaction.…”

Fiber optic Raman spectrograph for in situ environmental monitoring. Final report

“…-> :CC12+ cr (3.4) The formation of the dichlorocarbene during the electrochemical reduction process would tend to form a ring type structure [34]. This ring type structure is indicated in our SERS spectra with the strong band at 1380 cm"1.…”

“…However, in our experiments no SERS spectra of the chlorinated hydrocarbons were observed unless the electrode was illuminated during the reduction step and thus a strictly electrochemical reaction can be ruled out.This "photo" induced result indicates the possibility of a photoelectrocher, ical process. Copper oxides are known to be p-type semiconductors which eject electrons under illumination (Equation I)[34]. The band gaps for the two possible copper oxides are 2.0-2.6 eV (620-477 nm) for Cu20 and 1.7 eV (730 nm) for CuO.…”

Electrochemical Phase-Transfer Catalysis in Microemulsions: Carbene Formation

“…This ion associates with a quaternary ammonium ion (such as tetrabutylammonium) and enters the organic phase where it loses chloride to give dichlorocarbene which can partake in a variety of reactions including cyclopropanation across a double bond. To date, electrochemical generation of this intermediate followed by trapping with an alkene has been carried out in dry solvent systems. , …”