714223-43-5Relevant academic research and scientific papers
Effect of the leaving group solvation on solvolytic behavior of benzhydryl derivatives
Denegri, Bernard,Kronjaa, Olga
, p. 495 - 503 (2009)
An effect of the leaving group (LG) solvation on reactivity of benzhydryl derivatives in SN1 reactions has been investigated by using X, Y-substituted benzhydryl phenyl carbonates, methyl carbonates, 3, 5-dinitrobenzoates (DNB), and the corresponding benzhydryl chlorides as reference compounds. Reaction constants (sf) derived from LFER equation log k (25°C)=sf (Nf+Ef) indicate that s f parameters of carbonates and DNBs decrease as the fraction of the water in a given solvent/water mixture increases, while those of chlorides remain unchanged. This phenomenon is due to less important solvation and less charge separation in the TS. Effects of the solvents on the reaction rates were analyzed by Grunwald-Winstein correlations using various solvent-ionizing power scales. The m values obtained for carbonates and DNBs are considerably smaller than the m values for chlorides. Also, the solvolysis rate constants of substrates that have stronger electrofuges are less influenced by solvent (lower m) than those with weaker electrofuges. Values of m parameters obtained for a given substrate in a given binary solvent system correlate well with the electrofugality of the generated benzhydrylium ion. Abscissa at which m=0 represents the extrapolated critical electrofugality Ecrit f of the substrates whose solvolysis rates should not depend on the water fraction in the aqueous/organic solvent mixtures. Similar values for the critical electrofugality have also been obtained from extrapolated logk versus Ef plots. Copyright
Molecular recognition of chiral diporphyrin receptor with a macrocyclic cavity for intercalation of aromatic compounds
Ema, Tadashi,Ura, Norichika,Eguchi, Katsuya,Sakai, Takashi
experimental part, p. 101 - 109 (2012/03/07)
Chiral diporphyrin receptor 1, which has a macrocyclic cavity for the intercalation of aromatic guest molecules, was designed and synthesized from pyrrole in five steps. The binding constants (Ka) revealed the greater affinity of 1 for more electron-deficient aromatic guests. The complexation between 1 and 1,3,5-trinitrobenzene (G8) (Ka = 1850M-1) was much stronger than that between porphyrin monomer 3 and G8 (Ka = 50M-1). This result strongly suggests that G8 was intercalated into the cavity of 1 via cooperative double π-π stacking. Interestingly, 1 enabled the naked-eye detection of an aromatic explosive G8; a dark-red solution of 1 in CHCl3 turned into a colloidal suspension upon addition of G8, and the light was scattered. Fluorescence spectroscopy was also useful for the selective detection of G8; fluorescence of 1 was quenched by complexation with G8, which was visible with the naked eye. Despite modest binding constants for dinitrobenzene derivatives, 1 showed a good ability to discriminate the enantiomers of twelve chiral compounds bearing a dinitrophenyl group by NMR spectroscopy. The MM calculations with the MM3 force field reproduced inclusion complexes between 1 and nitroaromatic compounds. The mechanism of chiral discrimination is proposed.
Kinetics of the solvolyses of benzhydryl derivatives: Basis for the construction of a comprehensive nucleofugality scale
Denegri, Bernard,Streiter, Andre,Juric, Sandra,Ofial, Armin R.,Kronja, Olga,Mayr, Herbert
, p. 1648 - 1656 (2007/10/03)
A series of 21 benzhydrylium ions (diarylmethylium ions) are proposed as reference electrofuges for the development of a general nucleofugality scale, where nucleofugality refers to a combination of leaving group and solvent. A total of 167 solvolysis rate constants of benzhydrylium tosylates, bromides, chlorides, trifluoroacetates, 3,5-dinitrobenzoates, and 4-nitroben-zoates, two-thirds of which have been determined during this work, were subjected to a least-squares fit according to the correlation equation log k 25°C = Sf(Nf + Ef), where s f and Nf are nucleofuge-specific parameters and E f is an electrofuge-specific parameter. Although nucleofuges and electrofuges characterized in this way cover more than 12 orders of magnitude, a single set of the parameters, namely sf, Nf, and E f, is sufficient to calculate the solvolysis rate constants at 25°C with an accuracy of ± 16%. Because sf ≈ 1 for all nucleofuges, that is, leaving group/ solvent combinations, studied so far, qualitative discussions of nucleofugality can be based on Nf.
