Malonic acid is also known as methane dicarboxylic acid, carrot acid, malic acid reduction, beet acid. There are three kinds of crystal forms, of which two are triclinic, and one is monoclinic. That crystallized from ethanol is white triclinic crystals. Its relative molecular mass is 104.06. The relative density is 1.631 (15 ℃). Melting point is 135.6℃. It decomposes to acetic acid and carbon dioxide at 140℃. It does not decompose at 1.067×103~1.333×103Pa vacuum, but directly sublimates. It is not soluble in benzene. It is soluble in water, and the solubility is respectively 61.1 (0 ℃), 73.5 (20 ℃), 92.6 (50 ℃) in water, and 57 (20 ℃)in ethanol, 5.7 (20 ℃) in diethyl ether. It is slightly soluble in pyridine. It can decompose to formic acid and carbon dioxide in case of potassium permanganate. Malonic acid is dibasic acid. It has a typical reactive of dibasic acids, such as that its methylene is active, and it can be an addition, alkylation, amination, halogenation reaction; its two carboxyl groups are very close and they can be dehydrated; esterification with alcohol; decarboxylation by heating; condensation with carbonyl compounds; addition with compounds that containing active double bonds. Hydroxyl in two carboxyl groups of malonic acid were all replaced by ethoxy (see substitution reaction) to produce diethyl malonate.
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