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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 23, Number 1
BKCSDE 23(1)
January 20, 2002 

Interpretation of Dispersion Phenomena in Grunwald-Winstein Correlation for Solvolyses of Naphthoyl Chloride
Zoon Ha Ryu, Chang-Suk Ju, Dae Dong Sung, Nak Chang Sung, T. William Bentley
Solvolysis, Dispersion, Grunwald-Winstein correlation.
Solvolyses rate constant of 1- and 2- naphthoyl chlorides (1 and 2) are reported for aqueous binary mixtures with methanol, ethanol, fluorinated alcohol, acetonitrile and dioxane. Kinetic solvent isotope effects (KISE) in methanol and product selectivities (S) of 2-naphthoyl chloride (2) in alcohol-water are also reported. Dispersions in Grunwald-Winstein correlations (r ≤ 0.901) are discussed by multiple regression analysis incorporating ionizing power (YCl) scale and rate-rate profiles. Major causes for these phenomena are investigated as an aromatic ring solvation effects, in conjunction with weakly nucleophilic solvation effects (SN2 character), for solvolyses of 1 and for solvolyses of 2, as dual reaction channels, described as SN1-SN2 and SAN-SN2 processes. Distinct border lines between the two pathways are derived from solvolyses rates of 2 in 18 solvent using the results of log(k/ko) = mYCl + lNT + hI plot with values of 1.13 for m, 0.37 for l and 0.15 for h value in 5 aqueous fluorinated alcohol mixtures. Using rate-product correlation, the validity of a third order model based on a general base catalyzed by solvent and contribution from these rate constants, kaa, kaw and kwa, are investigated for SAN/SN2 solvolyses of 2 favored in more rich alcohol media and gradual addition of water to alcohol solvent shows a great shift away from stoichiometric solvation to predominantly medium effects. Rate-rate correlation between solvolyses of 2 and trimethyl acetylchloride (5) with alkyl group in the 29 aqueous solvent mixtures shows appreciable linearity (slope = 0.84, r = 0.987), caused by the same pathway (SN1-SN2 process), even if this correlation coincides with appreciable dispersion (different solvation effect).
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