Question

can methyl malonic acid be converted into propanoic acid on heating? if yes what is the mechanism?

Answer 1

2-methylpropanedioic acid is methylmalonic acid

Answer 2

Yes it will decarboxylate.
It first forms COO- which leaves as CO2.

Answer 3

why does it form COO-. isn't it unstable?

Answer 4

The Well COOH is acidic isn't it? So H+ can easily leave forming COO- and the negative charge on O comes in and the C-C bond breaks to release CO2 and dcarboxyation is complete.