scholarly journals LINEAR FREE ENERGY RELATIONSHIPS CONCERNING REACTION RATES IN MODERATELY CONCENTRATED MINERAL ACIDS

1966 ◽  
Vol 44 (16) ◽  
pp. 1917-1931 ◽  
Author(s):  
J. F. Bunnett ◽  
Fredric P. Olsen
Keyword(s):  
Free Energy ◽  
Transition State ◽  
Reaction Rates ◽  
Mineral Acid ◽  
Linear Free Energy Relationships ◽  
Linear Free Energy ◽  
Linear Relationships ◽  
Mineral Acids ◽  
Energy Relationships ◽  
Better Than

Linear relationships exist between log kψ + H0 (for reactions of weakly basic substrates) or log kψ (for reactions of strongly basic substrates) and (H0 + log [H+]). These are linear free energy relationships. For weakly basic substrates, the correlations obtained are better than in plots of (log kψ, + H0) versus log [Formula: see text] or of log kψ versus −H0. The slopes in plots of log kψ or (log kψ + H0), as appropriate, against (H0 + log [H+]) are taken as parameter, [Formula: see text], which characterizes the response of the reaction rate to changing mineral acid concentration. Values of [Formula: see text] for reactions of strongly basic substrates reflect only relationships between protonated substrate and transition state, and may be related to reaction mechanism. [Formula: see text] values for reactions of weakly basic substrates reflect both equilibrium protonation of the substrate and transformation of protonated substrate to transition state, and are therefore less directly related to mechanism. However, the [Formula: see text] values for the two steps are additive and that for the latter step can be obtained by subtraction if the overall [Formula: see text] value and that for equilibrium protonation are known.

LINEAR FREE ENERGY RELATIONSHIPS CONCERNING EQUILIBRIA IN MODERATELY CONCENTRATED MINERAL ACIDS: A SIMPLE METHOD FOR ESTIMATING pK's OF WEAK BASES

1966 ◽  
Vol 44 (16) ◽  
pp. 1899-1916 ◽  
Author(s):  
J. F. Bunnett ◽  
Fredric P. Olsen
Keyword(s):  
Free Energy ◽  
Acid Concentration ◽  
Standard Form ◽  
Acidity Function ◽  
Linear Free Energy Relationships ◽  
Simple Method ◽  
Linear Free Energy ◽  
Equilibrium Quotient ◽  
Mineral Acids ◽  
Energy Relationships

Linear relationships exist between the logarithms of equilibrium quotients, [SH+]/[S][H+], of diverse bases as they vary with acid concentration in moderately concentrated mineral acids. For purposes of formulating these linear free energy relationships in standard form, the equilibrium quotient for protonation of a hypothetical aromatic primary amine of pKa zero has been chosen as horizontal coordinate; this is given by (−H0 − log [H+]). Log ([SH+]/[S]) + H0 is plotted against (H0 + log [H+]). The slope, [Formula: see text] of the linear plot is a parameter which characterizes the response of the equilibrium quotient to changing acid concentration. The intercept represents the thermodynamic pKa of the base. This constitutes a general method for estimating the pKa of any base which undergoes protonation in moderately concentrated mineral acid, with reference to the single acidity function, H0. For bases of diverse type, pK's estimated by this method are in good agreement with those estimated by the acidity function method. Use of the new correlation procedure as a check on the validity of several acidity functions and its application to equilibria not involving proton gain or loss are also discussed.

Linear free energy relationships in CN bond dissociations in molecular ions of 4-substitutedN-(2-furylmethyl)anilines in the gas phase

2007 ◽  
Vol 42 (11) ◽  
pp. 1496-1503 ◽  
Author(s):  
Eduardo A. Solano Espinoza ◽  
Elena Stashenko ◽  
Jairo Martínez ◽  
Uriel Mora ◽  
Vladimir Kouznetsov
Keyword(s):  
Free Energy ◽  
Gas Phase ◽  
Molecular Ions ◽  
Linear Free Energy Relationships ◽  
Linear Free Energy ◽  
Energy Relationships
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