29836-96-2

Upstream product

• 62-53-3 aniline 
• 405260-79-9 N-{[5-[(dimethylamino)methylene]-1,3-cyclopentadien-1-yl]methylene}-1,2,4-triazole-4-amine 
• 405260-80-2 C₁₁H₁₃N⁽¹⁵⁾N₄ 
• 696-68-4 6-(dimethylamino)fulvene 

Relevant academic research and scientific papers

Symmetry of O-H-O and N-H-N hydrogen bonds in 6-hydroxy-2-formylfulvene and 6-aminofulvene-2-aldimines

The symmetry of the hydrogen bonds in 6-hydroxy-2-formylfulvene and two N,N′-diaryl-6-aminofulvene-2-aldimines is probed by the NMR technique of isotopic perturbation. Observed deuterium-induced 13C NMR isotope shifts at several positions can be attributed to a combination of an intrinsic shift and the perturbation of a tautomeric equilibrium. The most dramatic are at the aldehydic or aldiminic carbon signals, where the observed isotope shift for the unlabeled carbon is +376 or +223 ppb. This large downfield shift is contrary to the small upfield shift expected for a four-bond intrinsic shift and can be attributed only to a perturbation shift. Therefore these intramolecular hydrogen bonds are asymmetric, the proton resides in a double-minimum potential surface, and each molecule exists as a pair of rapidly interconverting tautomers, regardless of solvent. The symmetry of the hydrogen bond is not governed only by the O-O or N-N distance. It is proposed that symmetric hydrogen bonds can be observed in crystalline phases but not as yet in solution because the disorder of the solvation environment induces an asymmetry of the hydrogen bond, whereas a crystal can guarantee a symmetric environment. These results provide no insight into the source of the stabilization attributed to low-barrier hydrogen bonds if they lack the special feature of symmetry.

Tautomerism in the solid state and in solution of a series of 6-aminofulvene-1-aldimines

To study systems able to sustain intramolecular proton-transfer, we have prepared a series of six aminofulvene aldimines including several labeled with 15N and 2H. These compounds show coupling constants through the hydrogen bond, 1hJ(15N-1H) and 2hJ(15N-15N). The position of the tautomeric equilibria, i.e., on what nitrogen atom is the proton, was determined in the solid state and in solution. The crystal structure of N{([5-[(phenylamino)methylene]- 1,3-cyclopentadien-1-yl]methylene})pyrrole-1-amine (3) has been determined by X-ray analysis. In solution, both N-H and C-H tautomers were observed and their structures assigned by NMR spectroscopy. Particularly useful is the value of the 1J(15N-1H) coupling constant.