Proton-transfer chemistry of urazoles and related imides, amides, and diacyl hydrazides

Abstract

The stabilty and the molecular properties of thiiranimine are studied by using ab initio MO methods. Geometries are optimized at the HF/631G* and MP2/631G** levels while relative energies are estimated at the MP4/631G** level together with the zero-point energies. Our analysis pointa out that the interaction between the C-N moiety and the three-membered ring is responsible for several unusual properties of thiiranimine such as the high C=N stretching frequency, the relatively small ring strain (as compared with thiirane), and the large proton affinity at nitrogen. Our calculations also suggest that the first photoelectron band is due to an S ionization and that the first UV band arisea ementially from an intraatomic sulfur transition. The fragmentation reaction is endothermic, but consideration of entropy terms modifies the picture significantly. The resulting free energies show that thiiranimine is quite stable towards fragmentation into hydrogen isocyanide plus thioformaldehyde in agreement with experiments on substituted thiiranimines. Finally, the regiochemistry of thiiranimine in cycloadditions is also discussed on the basis of the frontier orbitals.

Racemic 1-methyl-1,2,4-triazolidine-3,5-dione (1-methylurazole). Definitive characterization of pyramidal hydrazide N atoms and racemate intermolecular hydrogen bonding

“…These observations do not support the recent statement by Bausch et al (1991) that a methyl substituent bonded to a hydrazyl N atom in urazole '...may be constrained to be relatively coplanar with the imide-urazolyl moiety', in their accounting for the acidifying effect on urazole by the introduction of a 1-methyl substituent.…”

“…For the comparative reactivity studies of urazoles (Kolb, Dworkin & Miller, 1994), (I) was prepared as reported by Bausch et al (1991) by refluxing equimolar amounts of methylhydrazine and biuret in 1-pentanol for 9 h. The mass of crystals from the cooled mixture was isolated by filtration and recrystallized from ethanol; small, colorless crystals, m.p. 517-518 K (corr; colorless melt) [literature m.p.…”

“…517-518 K (corr; colorless melt) [literature m.p. 518-519 K (Bausch et al, 1991)]. An ethanolic solution of these crystals, evaporated very slowly, provided thick colorless crystals, m.p.…”

The structure of hydantoins in solution and in the solid state

“…Bausch et al [20,21] proved the acidity of hydantoin and 1-methylhydantoin, respectively, to be similar in DMSO (pK~ = 15.0 and 14.7, respectively [21a]) and water (pKs = 9.0 and 9.1, respectively [21b]). Surprisingly, in contrast to the sequence in urazole [20,21], in hydantoin and hydantoin derivatives the imide N(3)--H proton was found to be sufficiently more acidic than the amide N(1)--H proton from detailed IH NMR spectroscopic studies [15,22], )SN NMR [14] and UV [23], and potentiometric measurements [24].…”

Synthesis and characterization of new polyamides derived from 4‐(4′‐aminophenyl)urazole and aliphatic diacid chlorides

“…4,5 The polymerization of 4-phenylurazole (PHU) with phosgene, terephthaloyl chloride, and epichlorohydrin has been reported to produce insoluble polymers. 6 The polymerization of PHU with aliphatic diacid chlorides yields soluble polyamides with an inherent viscosity of 0.39 dL/g. 7 The copolymerization of 4-cyclohexylurazole (CHU) with aliphatic diacid chlorides produces soluble polyamides.…”