Won Heui Lee, H. Maskill
1994
Citations
0
Influential Citations
2
Citations
Journal
Journal of The Chemical Society-perkin Transactions 1
Abstract
The 4,4′-dimethoxytrityl carbenium ion has been generated in 80 : 20 (v/v) water–methanol containing perchloric acid in a rapid reaction from 4,4′-dimethoxytrityl alcohol and in a slower reaction from 4,4′-dimethoxytritylamine. The pKR+(–0.95; KR+= 8.98) and molar absorptivity (IµR+= 297 000) of the cation have been measured directly under equilibrium conditions in this highly aqueous medium at ionic strength = 1.0 mol dm–3 by a convenient spectrophotometric method at 25 °C. In addition, the pKR+ has been measured at other temperatures, which allows the determination of the standard enthalpy (ΔH⊖=–11.4 kJ mol–1) and entropy (ΔS⊖=–20 J K–1 mol–1) of the reaction of the cation with the solvent, and at other ionic strengths. The equilibrium constant for the formation of 4,4′-dimethoxytrityl chloride from the cation and chloride has also been measured in the same medium (KRCI= 8.20 at 25.0 °C, ionic strength = 1.0 mol dm–3) by generating the cation from the alcohol and perchloric acid in the presence of 0.10 mol dm–1 sodium chloride.