Exchange of labile bonded hydrogen

Such exchange reactions have preparative importance when the compound 

Shatenstein, Isotopenaustausch und Substitution des Wasserstoffs, VEB Deut-scher Verlag der Wissenschaften, Berlin, 1963. 

Decarboxylation is, of course, easiest when the carboxyl group is loosened by the influence of neighboring groups. Malonic acid18 and suitable substitution products73 can, after deuteration, be readily converted into deuterated acetic acid and its derivatives. Moreover, the simplest carboxylic acid, formic acid, has been obtained labeled in this way 74,75 

Anhydrous oxalic acid (10 g) was recrystallized three times from D20 (9 ml), the crystals being purified each time by sublimation at ca. 1 mm. The resulting [D2]oxalic acid was pyrolysed by being sublimed at ca. 1 mm through a 10-inch column filled with glass pieces and heated at 220°. The [D2]formic acid formed was collected in a dry box, the yield being 2.2 g from 8.8 g of [D2]oxalic acid, i.e., 98% b.p. 44-44.5°C/58 mm n20d 1.3692. 

The [D2]formic acid was treated twice with a ten-fold excess of distilled water. [1-Dxl-Formic acid was isolated from the aqueous phase by saturation with CuS04 and six extractions with anhydrous ether. The ether layer was dried over anhydrous CuS04 and distilled. B.p, 63°/145 mm w20D 1.3674. 

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