14039-18-0Relevant academic research and scientific papers
1H and 13C NMR detection of the carbocations or zwitterions from Rhodamine B base, a fluoran-based black color former, trityl benzoate, and methoxy-substituted trityl chlorides in the presence of alkali metal or alkaline earth metal
Hojo, Masashi,Ueda, Tadaharu,Yamasaki, Masanori,Inoue, Akihiko,Tokita, Sumio,Yanagita, Mitsuhiro
, p. 1569 - 1576 (2007/10/03)
The cleavage of C-O bonds in two fluoran-based dyes by the addition of alkali metal (M+ = Li+, Na+) and alkaline earth metal (M2+ = Mg2+, Ba2+) perchlorates in acetonitrile solution was exa
Reactivity in acid-catalyzed carbon-carbon heterolysis
Cao, Weiguo,Erden, Ihsan,Grow, Richard H.,Keeffe, James R.,Song, Jiangao,Trudell, Mary B.,Wadsworth, Teri L.,Xu, Fu-Pei,Zheng, Ji-Bin
, p. 1009 - 1034 (2007/10/03)
Equilibrium and rate constants have been determined for the acid-catalyzed heterolysis of two alcohols, 9-xanthydrol and p-anisyldiphenylmethanol, and two sulfides, (9-xanthyl) methyl sulfide and (7-tropyl) methyl sulfide. These data together with literature information are compared with rate constants for acid-catalyzed C-C heterolysis of several (9-xanthyl) compounds, (7-tropyl) compounds, a set of 3-arylcyclobutanones, and two 2-arylnitrocyclopropanes, all of which fragment to carbocations plus a carbon-centered nucleofuge. The fragmentation mechanisms are shown to be A1 or A1(ion pair) except for the 2-arylnitrocyclopropanes which cleave in trifluoroacetic acid by a concerted mechanism. Rate comparisons among several unstrained substrate sets indicate that O-centered nucleofuges undergo acid-catalyzed heterolysis ca. 103-104 faster than S-centered nucleofuges and ca. 109-1014 faster than the C-centered nucleofuges used here. Factors assisting C-C heterolysis (and their effectiveness) include the acidity of the medium (strong); the basicity and nucleofugality of the nucleofuge (moderate); the stability of the electrofugic carbocation (strong); and relief of ring strain (enormous). Compared with acyclic cleavages, rate accelerations worth ca. 15 kcal/mol (for cyclobutanones) and ca. 27 kcal/mol (for nitrocyclopropanes) are found. These effects are discussed in terms of transition-state structure, aided by computational evidence.
The Effect of Both ?-Donor Substituents and Acid Media on the Formation of Trityl Cations, Studied by Relaxation Methods and NMR-Spectroscopy
Blumenstock, H.,Dickert, F.,Fackler, H.,Hammerschmidt, A.
, p. 157 - 170 (2007/10/02)
Trityl trifluoroacetates were taken to study why ion formation from ionogens is favoured by acid media.From relaxation measurements, NMR-spectroscopy and conductivity studies it was found that this effect is due to anion solvation by acid, namely a specific solvation of the free anions and a statistical solvation of the anions bound in the ionogen.This leads to a drastically reduced ion recombination rate constant even at low concentrations of acid and an increased dissociation rate constant at rather high concentrations of acid. -.Keywords: Kinetics/ Ion solvation/ Carbenium ions/ NMR-spectroscopy
