Current Organic Chemistry - Volume 13, Issue 3, 2009

Polyphenols are a very diverse class of compounds. In the present volume the emphasis is on Schiff bases and azo compounds containing one or more hydroxy group. Such polyphenols have many interesting properties and uses. Photochromism is an extremely important feature to be used in many context in society. o-Hydroxy Schiff bases show this feature in a number of cases. A model for the process is now suggested. X-ray Read More

The main problem in the quantitative analysis of tautomeric compounds is that the individual tautomers cannot be physically separated. As a result, quantitative analysis, which requires calibration, is in general impossible. This is a general problem for molecular spectroscopy and gives rise to many chemometric approaches for the treatment of existing spectral data, all of them developed to overcome the lack of individual spe Read More

In many cases, the cofactors of biologically important proteins are linked to their apoproteins by Schiff bases. In this review we discuss three classes of proteins in which Schiff bases are crucial for their function and catalytic mechanisms. First, we focus on retinylidene proteins, in which the cofactor retinal is fixed to the apoprotein by a protonated Schiff base. Light induced retinal isomerization triggers a photocycle or a Read More

This review reports a systematic investigation, carried out on the Cambridge Crystallographic Database (CSD), on the structural features of iminoalkyl-phenols (or naphthols) as well as azo-phenols (or naphthols). All these compounds form N-H…O/O-H…N intramolecular hydrogen bonds assisted by resonance (RAHB) in tautomeric equilibrium which can be finely tuned by the substituents. Accordingly, they can present rev Read More

Schiff bases of salicylaldehyde with amines (anils) comprise a chemical system undergoing hydrogen-atom tautomerism between enol and keto forms and show the phenomena of solid state photochromism and thermochromism. However, the photochromic phenomenon is exhibited not only in the crystalline state but in solution and rigid glasses as well. The extensive investigations on the system converge to a general sc Read More

The specific features of intramolecular OH···N hydrogen bonds in o-hydroxyphenyl Schiff bases are discriminated. They are identified as resonance assisted low-barrier hydrogen bonds. The properties of such bridges are best reflected in infra-red absorption spectra and particularly in the stretching OH or NH bands. As shown, the most characteristic is the low intensity of these bands. The discussion is presented for a numb Read More