Mixtures of barium acrylate-methacrylate were prepared by crystallization from an aqueous solution of acrylic and methacrylic acids in molar ratios ranging from 1/9 to 4/6. Thermal reaction of the above mixed salts in the solid state under reduced pressure gave four different dimers, dimethyl 2-methylene-4-methylglutarate [1], dimethyl 2-methylene-4, 4-dimethylglutarate [2], dimethyl 2-methyleneadipate [3] and dimethyl 2-methylene-5-methyladipate [4]. On the other hand, the mixed salts of magnesium, calcium and strontium gave dimers[3] and [4]. Dimers[1]and [3] were obtained in the yield of 12.8% and 3.9%, respectively, when the mixture with the molar ratio of 2/8 was heated for 3 h at 210°C. In the case of the strontium salt, [3] was obtained in 7% yield heating the equimolar mixture for 2 h at 220°C. The change of the crystal lattice measured by X-ray analysis showed that the lattice structure of the barium salt was not destroyed as a whole but that of the strontium salt was disordered by heating.
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