Intramolecular hydrogen bonding in the lowest excited singlet states of some substituted salicylic acids

1968 ◽  
Vol 72 (9) ◽  
pp. 3297-3299 ◽  
Author(s):  
Stephen G. Schulman ◽  
Herman Gershon
Keyword(s):  
Hydrogen Bonding ◽  
Intramolecular Hydrogen Bonding ◽  
Excited Singlet ◽  
Singlet States ◽  
Excited Singlet States ◽  
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.

EFFECT OF INTRAMOLECULAR HYDROGEN BONDING ON IONIZATION CONSTANTS OF SUBSTITUTED SALICYLIC ACIDS

1966 ◽  
Vol 44 (11) ◽  
pp. 1261-1269 ◽  
Author(s):  
G. E. Dunn ◽  
Fei-lin Kung
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Spectrophotometric Method ◽  
Chelate Ring ◽  
Substituent Effects ◽  
Intramolecular Hydrogen Bonding ◽  
Ionization Constants ◽  
Intramolecular Hydrogen ◽  
Hammett Relationship ◽  
Salicylic Acids

Ionization constants at 25 °C have been determined by a spectrophotometric method for 17 substituted salicylic acids. These have been fitted to the simple Hammett relationship and to the extended one proposed by Jaffe, which takes into account the transmission of substituent effects by the o-hydroxy group. The results with Jaffe's equation show that substituent effects on acidity are transmitted only slightly, if at all, through the intramolecular hydrogen bond of a chelate ring. Possible interpretations of the results are discussed.

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