Cyanoacetic acid [372-09-8] C3H3NO2, M 85.1, m 70.9-71.1°, pK25 2.47. Recrystallise the acid to constant melting point from *benzene/acetone (2:3), and dry it over silica gel. [Beilstein 2 H 583, 2 I 253, 2 II 530, 2 III 1626, 2 IV 1888.] Cyanoacetamide [107-91-5] C3H4N2O, M 84.1, m 119.4°, is crystallised from MeOH/dioxane (6:4), then water and dried over P2O5 under vacuum. [Beilstein 2 IV 1891.] Cyanoacetic acid hydrazide [140-87-4] C3H5N3O, M 99.1, m 114.5-115°, crystallises from EtOH. The hydrochloride has m 178-180° and the benzylidene derivative has m 178°. It is converted to 3-oxo-5-iminopyrazolidine in hot 40% aqueous NaOH. [Beilstein 2 H 591, 2 I 256, 2 III 1636.] IRRITANT.

Cyanoguanidine (dicyandiamide) [461-58-5] C2H4N4, M 84.1, m ...

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