18102-38-0Relevant articles and documents
Substituent effects on aromatic stacking interactions
Cockroft, Scott L.,Perkins, Julie,Zonta, Cristiano,Adams, Harry,Spey, Sharon E.,Low, Caroline M. R.,Vinter, Jeremy G.,Lawson, Kevin R.,Urch, Christopher J.,Hunter, Christopher A.
, p. 1062 - 1080 (2007/12/27)
Synthetic supramolecular zipper complexes have been used to quantify substituent effects on the free energies of aromatic stacking interactions. The conformational properties of the complexes have been characterised using NMR spectroscopy in CDCl3, and by comparison with the solid state structures of model compounds. The structural similarity of the complexes makes it possible to apply the double mutant cycle method to evaluate the magnitudes of 24 different aromatic stacking interactions. The major trends in the interaction energy can be rationalised using a simple model based on electrostatic interactions between the π-faces of the two aromatic rings. However, electrostatic interactions between the substituents of one ring and the π-face of the other make an additional contribution, due to the slight offset in the stacking geometry. This property makes aromatic stacking interactions particularly sensitive to changes in orientation as well as the nature and location of substituents. This journal is The Royal Society of Chemistry.
Nitration in Aqueous Nitric Acid: the Rate Profile and the Limiting Reaction Rates
Draper, Mark R.,Ridd, John H. A.
, p. 94 - 99 (2007/10/02)
Rate coefficients for the nitration of a series of quaternary ammonium ions have been used to establish a rate profile for reaction in 63.7percent-100percent nitric acid at 25 deg C and to estimate the concentration of nitronium ions in the aqueous media.The kinetics of nitration of a series of reactive aromatic aromatic compounds (mainly phenolic ethers) in aqueous nitric acid have been analysed in terms of a first-order rate coefficient and the zeroth-order rate of formation of the nitronium ion.The first-order rate coefficients approach a limiting value as the reactivity of the aromatic substrate is increased and this value is as expected for the rate-limiting formation of an encounter pair (ArH*NO2+).The lifetime of nitronium ions in 60.4percent nitric acid (t1/2 ca. 5 x 10-8 s) has been calculated from the zeroth-order rate at 25 deg C and used to show that the formation of the encounter pair (ArH*NO2+) occurs by the diffusion together of the components, not by pre-association.The studies on the more reactive aromatic compounds were carried out in the presence of hydrazine since this was shown to prevent the nitrous-acid catalysed reactions previously observed.
