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kilomentor | 24 October, 2007 13:32
Expired US patents 4,332,968 and 4,306,068 contain a chemical trick that can be used to remove water from many wet liquids. Apparently if mesityl oxide, (Me)2C=CH-CO-Me, is added to the wet liquid in the stoichiometry of 1 mole of mesityl oxide for each mole of water and a catalytic amount of a primary amine is added and the liquid is then warmed up two equivalents of acetone will form as the acetone is distilled out of the mixture.
The mechanism of the process has been studied by Ralph M. Pollack and David Strohbeen, J. Am. Chem.. Soc. (1972), 94(7), 2534-5. One can imagine that the method could be used to de-water liquids that are difficult to dry by other means such as DMSO, DMF, etc. The method would certainly efficiently dry lower molecular weight water-miscible primary amines, where the catalyst would be present in enormous excess.
The two patents are directed to other very practical uses. Reaction of a mixture of a primary and a non-primary amine by heating the mixture together with mesityl oxide results in a mixture of the imine of the primary amine with acetone, and unreacted non-primary amine. The patents teach that where the amine mixture cannot be separated by distillation, the new mixture of imine and non-primary amine usually can be.
Another use claimed by these lapsed patents is a means to make the imine quantitatively as a protecting group for the primary amine.
It is not known what range of other functional groups can be tolerated by this method which destroys water by converting it to acetone, but the possibilities are large. As far as I can tell, this methodology has not been used outside of these publications. Of course, one of the problems with process patents is that the users do not publicize that they have been infringing the monopoly.
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