The influence of intramolecular hydrogen bonding on proton-transfer reactions. A temperature-jump study of acid-base reactions involving substituted salicylic acids

1984 ◽  
Vol 88 (19) ◽  
pp. 4229-4232 ◽  
Author(s):  
H. Diebler ◽  
F. Secco ◽  
M. Venturini
Keyword(s):  
Hydrogen Bonding ◽  
Proton Transfer ◽  
Temperature Jump ◽  
Intramolecular Hydrogen Bonding ◽  
Transfer Reactions ◽  
Acid Base ◽  
Proton Transfer Reactions ◽  
Intramolecular Hydrogen ◽  
Salicylic Acids

Effect of intramolecular hydrogen bonding on the relative acidities of substituted salicylic acids in benzene solution

1967 ◽  
Vol 45 (14) ◽  
pp. 1699-1706 ◽  
Author(s):  
G. E. Dunn ◽  
Thomas L. Penner
Keyword(s):  
Hydrogen Bonding ◽  
Electronic Effect ◽  
Benzene Solution ◽  
Intramolecular Hydrogen Bonding ◽  
Acid Strength ◽  
Carboxyl Group ◽  
Hammett Equation ◽  
Phenolic Group ◽  
Intramolecular Hydrogen ◽  
Salicylic Acids

The relative acidities of fifteen 4- and 5-substituted salicylic acids were determined in benzene solution by potentiometric titration. The potentials at half neutralization (h.n.p.) relative to that of salicylic acid were considered to measure the acidities of the substituted acids relative to the parent acid. These potentials, designated by Δhnp, gave a significantly better correlation with Hammett's sigma constants in an equation of the form proposed by Jaffe, Δhnp = ρ1σ1 + ρ2σ2, than in a simple Hammett equation, Δhnp = ρ1σ1. In these equations the subscripts 1 and 2 refer to the position of a substituent relative to the carboxyl group and to the phenolic group respectively. The value of ρ2/ρ1 was found to be 0.4, indicating that the electronic effect of a substituent on the acid strength via the phenolic hydrogen-bonded path is almost half as large as the direct effect through the carboxyl group. These results, together with the fact that in aqueous solution there is very little if any transmission via the phenolic group, are discussed in terms of intramolecular hydrogen bonding of salicylic acids in benzene and in water.

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