t buoh 10ex 635 0 h sub 2 o 80 ca oh sub 2 62 0 7 70 63 iproh 20__________________________________________________________________________ abbreviations employed in table 1 yld of mma yield of methylmalonic acid based on the acrylic acid charged t buoh 2methyl 2 propanol iproh 2propanol the method of examples 1 to 6 was repeated except the methylmalonic acid was isolated at the end of the reaction 48 hours the isolation treatment comprises cooling the final reaction mixture to approximately 25 u00b0 c and then separating by filtration insoluble part a which is calcium methylmalonate and calcium hydroxide from the filtrate b the filtrate was stirred in air overnight and then filtered to remove the iron salts the new filtrate was added to the solid fraction a and the solution thus obtained was neutralized with dilute hydrochloric acid this solution was then saturated with sodium chloride and was extracted with five 200 cm 3 portions of ethyl ether the ethyl ether solution was dried over mg sulphate by the evaporation of the solvent at reduced pressure the evaporated solvent contain unreacted acrylic acid and traces of propionic acid which were formed after drying a solid was recovered and weighed the purity.