No abstract

No abstract

No abstract

The adsorptive interactions of 2-propanol (2-PrOH) molecules with silica surfaces were investigated using ab initio and density functional calculations. Two cluster models of silica were chosen to represent the terminal ≡SiOH groups and the siloxane bridges ≡Si-(O) 2-Si≡ on the silica surface. The Hartree-Fock (HF) and Density Functional Theory (DFT) approaches, employing a 6-31G(d) basis set, were used to calculate the geometries, electronic structures, vibrational frequencies and adsorption energies of the adsorption complexes formed. The calculated adsorption energies were corrected for zero-point vibrational energies (ZPVE) and basis set superposition errors (BSSE). The results favoured a most likely surface configuration for the physisorbed species in which 2-PrOH molecules are bound to exposed silanol groups via two hydrogen bonds, with the alcoholic-OH group acting simultaneously as a proton acceptor and donor. Moreover, bonding of 2-PrOH with strained surface siloxane bridges (≡Si-O-Si≡) was shown to lead to chemisorption of the alcohol molecule. These findings have been shown to help interpreting reported infrared spectroscopic results of in-situ experimental studies.

Abstract4‐Arylidenimino‐3(2H)‐thioxo‐1,2,4‐triazin‐5(4H)‐ones (1a–e) and 4‐arylidenimino‐3‐methylthio‐1,2,4‐triazin‐5(4H)‐ones (2a–e) were synthesized. Pyrolytic deprotection of these substrates were carried out. The kinetic results, product analysis and theoretical studies lend support to a reaction pathway involving a six‐membered transition state in which the carbonyl and not thione bond attacks the hydrogen atom of the arylidenimino group. This reaction represents an efficient, clean and general synthetic procedure for the protection and selective synthesis of potential biologically active triazines and their derivatives. Copyright © 2003 John Wiley & Sons, Ltd.

No abstract