Heterolytic mechanisms definition

A net heterolytic H2 cleavage was evidenced for [Pd(Salen)] (2 in Scheme 4.2) [29, 30]. Its catalytic activity was pH-dependent namely, it was inhibited by acids and enhanced by bases. A kinetic study of the hydrogenation of 1-hexene in DMF led to the definition of the following mechanism (Scheme 4.10) ... 

In this chapter, the basic principle of arrow pushing was introduced in the context of organic reactions driven by homolytic cleavage, heterolytic cleavage, or concerted mechanisms. Furthermore, the concept of polarity was introduced using heteroatoms and common organic functional groups. This discussion led to the definitions of nucleophiles and... 

By far the most evidence for electrophilic sulphur is found in the sulphenyl halides (RSCl, RSBr) Although these compounds may in theory react either as sources of RS or X (X = halogen), none of the observed reactions of the sulphenyl halides indicate the latter mode of heterolysis. Kharasch et have presented good evidence for the existence of the 2,4-dinitrobenzene-sulphenium ion (Ar ) in strongly acidic media evidence has also been presented of a strong solvent effect upon the rate of reaction of 2,4-dinitroben-zenesulphenyl chloride and cyclohexene - and of a definite substituent effect in the reaction of this sulphenyl chloride with some substituted styrenes in acetic acid . Such observations are entirely consistent with an electrophilic heterolytic ad tion mechanism involving attack by the sulphenyl chloride in the sense iC -Cl. 

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