Acid-base behaviour in non-aqueous solvents

Acid-base behaviour in non-aqueous solvents Bromine trifluoride... 

This result, like that found for sulfur dioxide, is somewhat ironic, as phosgene played an important rdle in the development of Franklin s theory of the acid-base behaviour of non-aqueous solvents [736,738a,850d,1285a], There has been a very recent suggestion, however, that [COCl]" is stabilized by a zeolite framework [641], and exhibits r(CO) at 1790 and 1710 cm [641], This claim requires substantiation, however. 

Only a very few solvents will be considered, chosen so as to illustrate a wide range of behaviour towards acids and bases, and these will include some in which the interaction with the solvent is so small that it is necessary to add a second acid-base pair (for example an indicator) before measurable equilibria are set up. We shall begin with qualitative descriptions, followed by a more quantitative treatment of a few examples. There now exist a number of comprehensive accounts of behaviour in non-aqueous solvents, and few references will therefore be given in this chapter. 

M. M. Davis, Bronsted Acid-Base Behaviour in Inert Organic Solvents, in The Chemistry of Non-Aqueous Solvents, ed. J. J. Lagowski, Acad. Press, Vol. 13 (1970). 

A surprising exception has been reported with evidence for a cleavage reaction in the case of divinyl sulphone. In non-aqueous and slightly acidic media, the behaviour of a., ji-unsaturated aromatic sulphones is also complex (see Table 7) since the cleavage and the saturation may compete. Strongly electrophilic double bonds undergo Michael additions in aprotic solvents by slowly protonated anions. Transfer of labile hydrogen may also lead to unactivated bases. It is noteworthy that in numerous cases (Table 6) the saturation is the preferred route. 

An example presented in Fig. 1.1.2 gives a visual presentation of the relative acidities and acid-base ranges of the most important non-aqueous protic and aprotic solvents. The positions of many known acid-base pairs are also presented on this scale. This scale illustrates the above-discussed phenomenon of the levelling of acidic and basic properties that can be seen from the following example concerning the behaviour of acetic acid as a solvent and as a dissolved substance in other solvents. There are three kinds of particles in the pure acetic... 

A non-aqueous analogue of the above examples of base hydrolysis in aqueous solution is solvolysis in acetic acid-acetate solutions. This reaction has been studied for tra/i -CCoCOgC-Rja engl+j where R = o-tolyl or p-tolyl, whose rates of solvolysis are found to decrease with increasing concentration of added acetate. This behaviour is in direct contrast to that of the aqueous system. In acetic acid the V lcb mechanism appears not to operate, and the mechanism must be solvent-assisted dissociation, with ion-pairs less reactive than the free cation. ... 

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