From Molecular Complexes to Zwitterions and Final Products. Reactions between C₃O₂ and Amines

Abstract

The formation of molecular complexes (prereactive intermediates) between C3O2 and amines (ammonia, dimethylamine, trimethylamine, and 4-(dimethylamino)pyridine) as well as the subsequent transformation of the complexes into C3O2−amine zwitterions in cryogenic matrixes (ca. 40 K) has been observed. In the case of dimethylamine, the formation of tetramethylmalonamide has also been documented. Calculations using density functional theory (B3LYP/6-31G(2d, p)) are used to assign all above species and are in excellent agreement with the IR spectra.

Theoretical Study of the Stereoselective Additions of Chiral Alcohols to Ketenes

“…Direct observation of ylide adducts of ketenes and pyridine, 16 − 18 , has been achieved in solid argon matrixes (ca. 40 K) using FTIR spectroscopy, with ketenes such as dibenzopentafulvenone and derivatives, − 19 − 21 , dicarboalkoxyketenes, 22 − 24 , dipivaloylketene, and phenyl and 1-naphthylketenes, 25 and 26 , shown in Figure . In these cases, where the negative charge can be efficiently stabilized by formation of an aromatic ring or by resonance delocalization onto an α-carbonyl group or aromatic ring, ab initio calculations indicated that zwitterion formation is mildly exothermic and has a low activation energy in the gas phase. , So far, no ketene-trialkylamine ylides have been observed experimentally in argon matrices, and this suggests that the delocalization of positive charge in the pyridine ring is also important in stabilizing the corresponding zwitterions.…”

Chemistry of Stable Iminopropadienones, RNCCCO

“…Thiazole forms a van der Waals complex with C 3 O 2 in the same manner as pyridine, , involving an interaction between the nitrogen lone pair and the cumulene system . Therefore, it may be expected that thiazoles and thiazolines react with ketenes in much the same manner as pyridines and that reaction with 6 will proceed analogously to Schemes and .…”

“…40 K), to produce ketene−pyridine zwitterions . Furthermore, carbon suboxide, OCCCO, reacts with pyridine and other amine nucleophiles in low-temperature matrixes to give, first, observable van der Waals complexes, which can be transformed into covalent zwitterions of the type OCCC(O - )Nu + . It is postulated that the corresponding zwitterion 17 can form by interaction of 2-(methylamino)pyridine with 6 .…”

“…Addition of the exocyclic amino group to the imine carbon atom in 17 affords the mesoionic heterocycle 18 . It would be possible to bypass 17 by postulating that the exocyclic amino group reacts with the less electrophilic CN carbon of the cumulene 6 , but this goes against all our knowledge of the initial stages of these and similar reactions. ,, This reaction is reversible: FVT of 18b at 350 °C regenerates 2-(methylamino)pyridine and 6b , as proved by the IR spectrum of the products in Ar matrix at 10 K. However, the mechanisms of the synthesis and fragmentation of 18c are likely to involve different intermediates. A rational mechanism for the FVT reaction is given in Scheme , and this is based on a previous investigation of ring opening and fragmentation in six-membered mesoionic compounds .…”

Zwitterion Formation in Titan Ice Analogs: Reaction Between HC3N and NH3

“…With regard to the IR and mass spectroscopic results, we can conclude that the aminoacrylonitrile is not the product formed. In view of these results, and the work obtained on the thermal reactivity of NH 3 on C 3 O 2 , 27 we considered the formation of a zwitterion between NH 3 and HC 3 N. To better understand the formation process of this new product, we have measured the experimental activation barrier. To study this reaction, we use a NH 3 :HC 3 N mixture in a 10.5:0.5 ratio and we measure the reaction rate as a function of temperature.…”