[Enthalpy]

Hello you all!

As a heat of formation for Guanidine HN=C(NH₂)₂ (solid, at 298K, from its elements in normal state...) I could only find:

• -56.0kJ/mol (for the solid at room temperature?), for instance at Nist;
• +15kJ/mol at Argonne (the ideal gas at 298K, isn't it?)

And I find it hard to believe.

Starting from gaseous methane (-75kJ), one single amine function already adds +52kJ. The next one shouldn't add less, and the double bond neither, should they? This would land near +80kJ for gaseous Guanidine, close to Am1 predictions.

All tables refer to a single Russian publication in 1968... Could it be that conventions differ(ed), meaning an endothermic compound, with +56.0kJ for the solid instead of -56kJ?

Or do you know other figures?

Thanks!