Chlorine generating demonstration

The chlorine generated can be used in an interesting reaction. The following demonstration is optional, but is useful to show students that it is not just oxygen that supports burning. 

The pH of the chlorine dioxide reaction mixture must be maintained in the 2.8—3.2 pH range, otherwise decreased conversion yields of chlorite to chlorine dioxide are obtained with by-product formation of chlorate. Generator efficiencies of 93% and higher have been demonstrated. A disadvantage of this system is the limited storage life of the sodium hypochlorite oxidant solution. 

The EPR spectra of the NHC boryl radicals that were generated through HAT to the ferf-butoxyl radical clearly show the delocalized 7i-type nature of these intermediates postulated to be essential by calculations [10, 12]. It was also demonstrated that the decay of the EPR signals could be fitted to a second-order decay having 2kt = 9 x 106 M-1 s-1. In agreement with this kinetic analysis, the NHC boryl radicals ultimately dimerize to give bis-NHC diborane derivatives. With the aid of EPR spectroscopy it was also established that the NHC boryl radicals readily abstract bromine atoms from primary, secondary, and tertiary alkyl bromides. However, chlorine atom abstraction is much slower and useful only for benzyl chloride. 

Ranzi et al. [13] demonstrated that the radical generation by initiation is by far more important than by chlorine elimination or C-C bond breaking. 

It was demonstrated that water electrolysis generates mixed oxidant systems. Oxidation-reduction potential (Hsu and Kao 2004) is not the best parameter for system characterisation. In general, the online analysis of generated species is an unsolved problem. Probably, not all electrolysis products are known. This can be seen in analysing the active and total chlorine concentration. The standard method uses DPD but the effect of other chemicals on the DPD method is one reason that active chlorine is sometimes incorrectly measured. Amperometric analysis and... 

Scheme 1 demonstrates that different products result in dependence on the type of coimection between the CH3SiCl3 molecule and the silicide cluster on the catalyst surface. The preferred connection over two chlorine atoms is plausible and seems to be the reason for the kinetically controlled generation of dichloromethylsilane. 

A number of low-grade transition metal ores (for example, minerals containing nickel oxides) can be used as catalysts. Smuda has demonstrated that microwave or radiofrequency irradiation of a mixture of such ores with a carbon source initiates reduction of the oxide to metal. With this approach, poisoning the active sites of the catalyst will not be critical for the process since there will be a constant supply and generation of active catalyst with the feed material. In addition to well-known catalytic properties of nickel in organic reactions, it was also shown that Ni on carbon and other supports, catalyzes hydrodechlorination and dehydrochlorination of chlorinated organic waste streams [22-24],... 

One can conclude that the 1-phenylethyl halide is by far the preferred product of these interactions, but that suitable conditions of polarity and temperature can create the conditions required for some polymerisation to take place. Pocket et al. have demonstrated that 1-phenylethyl chloride exchanges chlorine atoms with HCl in nitromethane, i.e., that carbenium ion pairs can be generated in tiiis system. It seems likely that the low yields of polymers observed in specific conditions as described above resulted from the solvation of the halide by excess acid, a contingency which restricted active species to a short period. From the few scattered results published it is nevertheless difficult to derive a sound interpretation of such apparent anomalies as the fact that the strongest of all hydrogen halides, HI, failed to induce polymerisation. 

---