Process for preparing substantially pure rhodinal

Claim 1

THE PROCESS OF MAKING PURE RHODINAL WHICH COMPRISES REACTING, AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 100*C. AND ABOUT 200*C., A MIXTURE, CONSISTING ESSENTIALLY OF RHODINAL AND CITRONELLAL, WITH A BORATING AGENT SELECTED FROM THE GROUP CONSISTING OF BORIC ACID, BORIC ACID ANHYDRIDE AND A LOWER ALKYL BORATE, SAID BORATING AGENT BEING PRESENT IN A RATIO OF ABOUT ONE-THIRD THE NUMBER OF ATOMS OF BORON TO THE TOTAL NUMBER OF MOLES OF CITRONELLAL AND ISOPULEGOL IN THE STARTING MIXTURE, IN THE PRESENCE OF A CATALYST FOR THE SELECTIVE ISOMERIZATION OF CITRONELLAL TO ISOPULEGOL, WHEREIN SAID CATALYST IS AT LEAST ONE MEMBER SELECTED FROM THE GROUP CONSISTING OF SILICON DIOXIDE, PHENOL, A MONOALKYL PHENOL, A DIALKYL PHENOL, A TRIALKYL PHENOL, BORIC ACID, FORMIC ACID, ACETIC ACID, PROPIONIC ACID, BUTYRIC ACID, VALERIC ACID AND THEIR MONO-ALKYL ESTERS IN WHICH SAID ALKYL GROUP HAS UP TO FIVE CARBON ATOMS; OXALIC ACID, MALONIC ACID AND SUCCINEIC ACID AND THEIR MONO-ALKYL AND DI-ALKYL, SAID CATALYST BEING PRESENT IN AN AMOUNT OF AT LEAST ABOUT 3 PERCENT, BY WEIGHT, BASED ON THE WEIGHT OF THE CITRONELLAL PRESENT IN THE STARTING MIXTURE, AND UNTIL SUBSTANTIALLY ALL OF THE CITRONELLAL HAS BEEN CONVERTED TO ISOPULEGOL, AND SEPARATING THE UNCHANGED RHODINAL FROM THE RESULTING ISOPULEGOL BORATE.