The Czech republic has a long tradition in explosives engineering the infamous ``Semtex" (hexahydro-1,3,5-trinitro-1,3,5-triazine) is a good example. Hence, if a high-ranking senior scholar from the Czech Academy of Sciences announces in a major newspaper interview:

``We discovered... a compound which is ... the strongest classical explosive known so far. It is one hundred times, possibly even one thousand times, stronger than trinitrotoluene, dynamite or nitroglycerin"

one should pay attention, especially if the information was later also published in THEOCHEM. But the army, navy and air-force didn't, not because the cold war is over but because the armed services are not paid to take attention of a mere play of words. Well, what went wrong?

The discoverer named the new species `Krakatene' (in a reference to the famous volcano Krakatoa or Krakatau). The formula of the species is C6. He had no experimental support for his claim that the substance explodes, which was based solely on theoretical speculation, and he gave only one argument in support of this: ``A ring of six carbon atoms is very rich in energy. We say that we have a compound with a very large positive heat of formation."

Small carbon clusters are not new. Otto Hahn and coworkers reported clusters up to C15 as early as 1942. They were never prepared in macroscopic amounts as condensed-phase chemical species. It is known that C4, C3, C2 and even C1 have heats of formation per carbon atom bigger than that of C6. Does this mean we should call them krakatene-4, krakatene-3, krakatene-2 or krakatene-1?

The heat of formation is a very useful quantity as it permits evaluation of the heat of reaction of any chemical process. However, it is a variable term which depends on the definitions of reference states and a stable species does not necessarily have a negative heat of formation. Notorious explosives exhibit positive as well as negative heats of formation. In fact, energy contents are not good predictors of explosive strength. The detonation of nitroglycerin yields about 6 kJ/g. Burning one gram of graphite gives 33 kJ (gasoline 47 kJ). What really matters is kinetics, reaction rates. Indeed, the time for complete reaction is by five orders of magnitude shorter in explosions than in fuel burning. If someone tries to 'invent' new explosives using pencil and paper, he/she should estimate reaction rates, not heats of formation! Hinshelwood and Semenov received the Nobel for such works in 1956.

Even before we discuss any kinetics -- potential explosives must be normally stable and producible in large quantities. C6 can only be prepared in small amounts in the gas phase or on inert-gas matrices. We can illustrate the point with N2. Let us take some its excited electronic state, say a quintet 900 kJ/mol above the ground state. Its heat of formation is about 33 kJ/g, considerably higher than that for C6. Should we speak of a super-Krakatene? Of course not -- we cannot produce the quintet in large amounts and store it.

It is virtually impossible to publish such a criticism in Czechia. People are afraid that it would further lower the shaky image of science. Hence, the clear nonsense, a Czech cold fusion, has still remained a discovery of the decade for some locals.

Zdenek Slanina

Acknowledgement: The author acknowledges the valuable remarks of Professor Ernest F. Silversmith, a leading expert in chemical etymology (see A. Nickon and E. F. Silversmith: Organic Chemistry: The Name Game, Pergamon Press, New York, 1987).

A partial bibliography of the explosive discovery: Young Front (March 20, 1993) J. Mol. Struct. THEOCHEM 313 (1994) 335, esp. p. 341 Chem. Listy 86, (1992) 162, esp. p. 164 General Chemistry, Karolinum (1994), esp. p. 211.