Novel reaction of N,N'-bisarylmethanediamines with formaldehyde. Synthesis of some new 1,3,5-triaryl-1,3,5-hexahydrotriazines.
The acid-catalyzed cyclocondensation of N,N'-bisaryl (aryl = 2-pyrimidinyl, 2-pyrazinyl and 4-nitrophenyl) methanediamines 5a-c with aqueous formaldehyde in refluxing acetonitrile leads to the formation of the corresponding 1,3,5-triaryl-1,3,5-hexa-hydrotriazines 6a-c. The stoichiometric reactions of 2-aminopyrimidine and 2-amino-pyrazine with aqueous formaldehyde in acetonitrile under reflux conditions also afforded 6a and 6b, respectively. Treatment of 2-aminopyrimidine with aqueous formaldehyde in a 3:2 ratio yielded N,N',N"-tris(2-pyrimidinyl)dimethylenetriamine (7a) as a sole product, which upon subsequent reaction with formaldehyde also afforded 6a. The reaction of N,N'-biphenylmethanediamine with formaldehyde was also investigated.
Computational and experimental studies on the mechanism of formation of poly(hexahydrotriazine)s and poly(hemiaminal)s from the reactions of amines with formaldehyde.
Combined experimental and computational studies have been performed on the mechanism of formation of poly(hexahydrotriazine) and hemiaminal dynamic covalent network (PHT and HDCN) thermosetting polymers from the reactions of diamines with formaldehyde (Science 2014, 344, 732-735). Results suggest that these polymers are formed by a mechanism involving the water promoted stepwise addition of amines with formaldehyde in preference to dimerization or cyclotrimerization of imine intermediates or self-catalysis by the amine reagents. The predicted mechanism also explains experimentally observed electronic effects for hexahydrotriazine formation.
The microwave spectrum, structure and dipole moment of aniline
Abstract The microwave spectra of thirteen isotopic modifications of aniline have been measured and a complete substitution structure of the planar C 6 H 5 N fragment has been determined. The C-N distance is found to be 1.402±0.002 A and the NH 2 group adopts an out-of-plane angle of 37° 29'±2° with the angle HNH 113° 6'±2°. The μ a component of the dipole moment has been measured as 1.129±0.005 D for the 0 + state and as 1.018±0.005 D for the 0 − state.