I have recently tried a preparation of calcium malonate using an older procedure by Subramaniam et al, as offered by DJF90. This procedure, as
excerpted, is shown below:
"Oxidation of Malic Acid by Hydrogen Peroxide in the Presence of Ammonia.
dl-Malic acid (5 g.) was dissolved in a 20-volume (6%) solution of hydrogen peroxide (100 c.c.), and the liquid was made just alkaline with
concentrated aqueous ammonia and diluted to 150 c.c. with water. After 30 hours the reaction mixture was shaken with animal charcoal (5 g.) to remove
the undecomposed hydrogen peroxide still present. The solution was filtered, boiled, and treated with an excess of calcium chloride solution. After
concentration to 100 c.c. and subsequent standing for 3 days, the white crystalline precipitate (5.25 g.) was collected, washed with water, and dried
in a vacuum [Found : Ca, 21.7. Calc. for CH2(CO*O)2Ca,2H2O: Ca, 22.3%].
A quantity of this calcium salt (1.5 g.) was heated in a sealed tube with glacial acetic acid (5 c.c.) and freshly distilled cinnamaldehyde (30 drops)
at 100° for 10 hours. The product was purified as detailed in a previous case and yielded 0.32 g., which melted at 208° (decomp.), alone or mixed
with authentic cinnamylidenemalonic acid of m. p. 208° (decomp.) (0.1510 g. required 27.4 c.c. of N/20 NaOH. Calc., 27.7 c.c.)."
A white precipitate of the stated weight was indeed obtained. However, extraction of the acidified salt with ether did not yield the desired
malonic acid.
Although a method for identifying the salt as a malonate is presented in the article, it appears cumbersome. Does anyone have any other suggestions
as to how putative Ca malonate can be identified? |
