accompanying speech (the asterisks instead of the spaces mark the clicks on the presentation):
Hello, I am Tiago Vieites Branco Fonseca and present*this, the substance named by*Heinrich Debus, who first isolated it,*glyoxaline. This name has been however made obsolete: the substance is now known as*imidazole.*It was formed at the time of its isolation from*ethanedial, or glyoxal, from which "glyoxaline" comes, and ammonia. As*Bronisław Leonard Radziszewski later found, there were actually*two reactions occurring: half of the ethanedial must first hydrolyse, as it is the resulting formaldehyde that forms with the other half of the ethanedial and the ammonia the imidazole. Now, just what exactly is formed? The chemical formula is not enough, the bonding arrangement is required. The*mechanism of the reaction would provide that but is unknown: nucleophilic addition necessarily occurs, the ammonia preferentially attacking the formaldehyde, followed by dehydration but the sequence stays undetermined. The dicarbonyl can be other than ethanedial, that is, the hydrogen can be substituted; "c" and "d" represent these generic groups, "a" and "b" will follow. Anyway,*this comes out. These are two generally different outcomes: 5-(c)-4-(d)imidazole is represented on the left and 4-(c)-5-(d)imidazole on the right. They are more precisely*tautomers, their relative predominance depending on the substituents, c and d. There are two other substitutable hydrogenous atoms so the ring can carry two more substituents, expectably on the leftover carbonaceous atom, bound to both nitrogenous ones, and one of them, becoming therefore*1,2,4,5-tetrasubstituted. 2-substitution, by employing some aldehyde other than formaldehyde, was already known in Radziszewski's time, along with both 4- and 5-substitution; 1-substitution followed, with some primary amine instead of half the ammonia. Both additional substituents can be however on the nitrogenous atoms, in which case the formaldehyde is employed but the other half of the ammonia is exchanged for some primary amine, though the reaction is slightly different as an*imidazolium is formed whose hydrogenous atom can leave, albeit difficultly. This may remind of the tautomers presented before but is resonance. The dehydronation, with a very strong base, of the cation gives the intended*1,3,4,5-tetrasubstituted imidazole. This awkward structure can be redrawn, avoiding the resonance and the formal charges, as a*carbene, which matches the behaviour.
