Production of pentenal

PROBLEM TO BE SOLVED: To produce pentenals in high selectivity and yield by hydroformylating 1,3-butadiene dissolved in an inert medium in the presence of an aqueous solution of a rhodium/phosphine complex compound as a catalyst. SOLUTION: 1,3-Butadiene is dissolved in a medium inert under reactional conditions (preferably propane, n-butane, etc.) and then hydroformylated in the presence of an aqueous solution containing a rhodium/phosphine complex as a catalyst and, as necessary, other phosphines at 100-180°C under 5-35MPa pressure. A compound of the formula [Ar 1 to Ar 3 are each phenyl or naphthyl; X 1 to X 3 are each a sulfonate or a carboxylate; Y 1 to Y 3 are each a halogen, CN - , etc.; (m 1 ) to (m 3 ) are each 0-5, with the proviso that at least one of(m 1 ) to (m 3 ) is ≥0; (n 1 ) to (n 3 ) are each 0-5; M is an alkali metallic ion; zinc ion, etc.] is preferred as the phosphine of the rhodium/phosphine complex compound. The catalyst is preferably prepared from rhodium or a rhodium compound and phosphine in the reactional mixture under the reactional conditions. COPYRIGHT: (C)1997,JPO