Chlorine cations

Fig. 4.3a. The change in the energy of LU, ezv and in the total energy, E, of ethylene-chlorine cation system...

Fig. 4.3 b. The changes in the LU partial population of pt orbital at -carbon ethylene-chlorine cation system... 

The next example for this rule may be the heterolytic addition of chlorine to the C=C bond. Fig. 4.3b indicates the partial valence-inactive population 60> of the 2pz AO of the /9-carbon in LU, calculated by the extended Htickel method. It is seen that this quantity, (c )2, largely increases according to the approach of the chlorine cation to the carbon atom at which the addition is to take place, so that the reactivity of the /9-position towards the second chlorine atom (anionic species) grows. Also Fig. 4.3a shows the decrease of the LU energy in the direction of the reaction path which has already been mentioned above. 

The structure of C1F6+ cation 338 has been established beyond any reasonable doubt by 19F NMR spectroscopy.818,843 The C1F6+ cation 338, except for the C102F2+ cation,845 is the only known heptacoordinate chlorine cation. Besides the well-known NF.4+ cation,846,847 it is the only known example of a fluorocation derived from the hitherto unknown compounds (i.e., NF5 and C1F7). Complete vibrational analysis of C1F6+ cation 338 has been reported,848 and it indicates the octahedral symmetry of the ion. 

Trifluoroacetyl hypochlorite dissociates into chlorine cation and trifluo-roacetoxy anion ... 

Cerium tetrakis(acetylacetonate), 1114 Cesium complexes crown ethers, 40 Chevrel phases, 1321 Chlorella vulgaris nitrate reductase structure, 1438 Chlorine cations... 

In mechanisms (1-2) and (3) it was assumed that the bare electrophilic reagent enters the substitution proper, e.g. the nitronium ion, the chlorine cation or the diazonium ion. There are, however, many electrophilic reagents which consist of the group to be introduced into the aromatic nucleus plus a basic component, e.g. benzoyl nitrate and dinitrogen pentoxide in nitrations (O2N—OCOAr and O N—ONOg), molecular bromine, the bromoacidium ion and hypobromous acid in brominations (Br—Br, Br—OHJ and Br—OH) etc. The question arises in which step the basic part of the electrophilic reagent is released. 

Hypochlorous acid directly reacts with organic nucleophilic compounds (X = O, N, S) or via the intermediate formation of the chlorine cation Cl " (HOCl — OH-+ CC Gallard and Gunten 2002, Hanna et al. 1991). Such reactions might also explain the formation of halogenated organic compounds in soils from OM such as humic material where the volatile fraction (for example chloroform) emits into air. All olefinic hydrocarbons and aromatic compounds add Cl and OH from HOCl (see for example reaction 5.422). 

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