Dimethyl sulfoxide acid catalysis

These complexes, unlike the crown ether complexes but similar to the aza-crown and phthalocyanine complexes, are fairly stable in water. Their dissociation kinetics have been studied and not surprisingly they showed marked acid catalysis.504 Association constant values for lanthanide cryptates have been determined.505,506 A study in dimethyl sulfoxide solution by visible spectroscopy using murexide as a lanthanide indicator showed that there was little lanthanide specificity (but surprisingly the K values for Yb are higher than those of the other lanthanides). The values are set out in Table 9.507... 

HO", to the enhancement of its activity in aqueous dimethyl sulfoxide as the concentration of water approaches low values.) Wang et al. (2011) demonstrated methylation of phenol and benzene-1,2-diol derivatives with 1,3,5-tiioxane (e.g.. Scheme A) in supercritical water, accelerated compared to the solvent-free reaction. The authors describe the reaction as uncatalyzed, though acid catalysis by water or by hydrogen ion is likely (see Section 3.6.1). 

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