Water can be used very advantageously as the solvent in homogeneous catalytic reactions and

thus gives rise to a specific class of aqueous biphasic reactions among two-phase reactions.

Thisnewuseof waterhastwoverypositiveconsequences: anadvantageouseffectonthe

selectivity of the homogeneous catalytic reactions and the opportunity, for the first time, to

“immobilize” the homogeneous catalyst by means of the “liquid support” water, then to sepa-

rate it simply and immediately from the reaction products after its task is complete and thus

to return it to the catalysis cycle. Apart from the industrial use of hydroformylation (oxo pro-

cess), finechemicalsarealsobeingincreasinglypreparedbytheaqueous, homogeneously

catalyzed biphasic technique.