Thermodynamic functions of ionization of t-butyl-substituted and methoxysubstituted phenols

1972 ◽  
Vol 25 (1) ◽  
pp. 75 ◽  
Author(s):  
PD Bolton ◽  
FM Hall ◽  
J Kudrynski
Keyword(s):  
Aqueous Solution ◽  
Thermodynamic Functions ◽  
Spectrophotometric Method ◽  
Substituent Effects ◽  
Steric Effects ◽  
Ionization Process ◽  
Ionization Constants ◽  
Temperature Range

Thermodynamic ionization constants of 2-t-butylphenol, 3-t-butylphenol, 4-t-butylphenol, 3,5-di-t-butylphenol, and 3,5-dimethoxyphenol have been measured in aqueous solution by an e.m.f./spectrophotometric method within the temperature range 5-60�C and the thermodynamic functions of ionization ΔG25, ΔH25, ΔS25, and ΔCp25 calculated. These results confirm the additivity of substituent effects noted previously for the ionization of 3,5-disubstituted phenols and indicate that this ionization process is relatively insensitive to steric effects.

Additive substituent effects on the ionization of meta-substituted phenols

1968 ◽  
Vol 21 (6) ◽  
pp. 1541 ◽  
Author(s):  
PD Bolton ◽  
FM Hall ◽  
J Kudrynski
Keyword(s):  
Thermodynamic Functions ◽  
Substituent Effects ◽  
Ionization Constants ◽  
Free Energies ◽  
Reaction Series ◽  
Substituted Phenols ◽  
Temperature Range

Thermodynamic ionization constants of 3-ethoxyphenol; 3,5-diethoxyphenol, 3,5-dichlorophenol, 3,5-dibromophenol, 3,5-diiodophenol, and 3,5-dinitrophenol have been measured spectrophotometrically within the temperature range 5-60�, and the thermodynamic functions of ionization ΔG25, ΔH25, ΔS25, and ΔCp.25 calculated. These results, in conjunction with others measured previously, indicate that, for this reaction series, substituent effects on the free energies of ionization are precisely additive, and on the entropies of ionization closely additive. An assessment of the results in terms of Hepler's internal/external enthalpy theory is made.

Substituent effects on the thermodynamic functions of ionization of metasubstituted anilinium ions

1968 ◽  
Vol 21 (4) ◽  
pp. 939 ◽  
Author(s):  
PD Bolton ◽  
FM Hall
Keyword(s):  
Linear Function ◽  
Thermodynamic Functions ◽  
Substituent Effects ◽  
Negative Slope ◽  
Hammett Equation ◽  
Reaction Parameter ◽  
Reaction Series ◽  
Acidity Constants ◽  
Temperature Range ◽  
Relationship Of

Thermodynamic acidity constants of the meta-methoxyanilinium, meta- chloroanilinium, meta-bromoanilinium, and meta-iodoanilinium ions have been measured spectrophotometrically over the temperature range 5-50� and those of the meta-nitroanilinium ion over the temperature range 5-60�. The thermodynamic functions of ionization, ΔG25, ΔH25, ΔS25, and ΔCp,25, have also been calculated for each ion. For a series of seven meta-substituted anilinium ions the acidity constants show close obedience to the Hammett equation over the temperature range 10-50� with the reaction parameter p being a precise linear function of 1/T. The same reaction series also shows a well-defined isoequilibrium relationship of negative slope.

scholarly journals Carbonyl Addition Reactions: Factors Affecting the Hydrate–Hemiacetal and Hemiacetal–Acetal Equilibrium Constants

1975 ◽  
Vol 53 (6) ◽  
pp. 898-906 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Compounds ◽  
Equilibrium Constants ◽  
Substituent Effects ◽  
Steric Effects ◽  
Addition Reactions ◽  
Free Energies ◽  
Electronic Effects ◽  
Factors Affecting ◽  
Analogous Formula

Equilibrium constants for hydrate–hemiacetal interconversion in aqueous solution at 25° have been measured for four fluorinated carbonyl compounds: compound, alcohol, K4 (M−1): CF3CHO, C2H5OH, 2.3; CF3COCH3, CH3OH, 1.0; CF3COPh, CH3OH, 3.5; CF3COCF3, CH3OH, 0.14. These values, combined with values from the literature, permit an examination of substituent effects upon the equilibrium constant for[Formula: see text]The free energy change for this process, corrected for symmetry and steric effects, follows the equation[Formula: see text]Thus electronic effects upon this equilibrium are generally small and in fact are often smaller than steric effects.This analysis permits and justifies the calculation of free energies of formation of [Formula: see text] compounds from the (more generally measurable) free energies of formation of the analogous [Formula: see text] compounds.

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.

Effects of Bromine Substituents on Rates of Acetate-promoted Enolization of Ketones

1972 ◽  
Vol 50 (19) ◽  
pp. 3242-3247 ◽  
Author(s):  
R. A. Cox ◽  
J. Warkentin
Keyword(s):  
Transition State ◽  
Carbonyl Group ◽  
Substituent Effects ◽  
Steric Effects ◽  
Ionization Constants ◽  
Polar Substituent ◽  
Methylene Group ◽  
Better Than

Effects of bromine substituents on rates of acetate-catalyzed bromination of ketones are reported. Approximate polar contributions to the rates were obtained, based on the approximation that the steric effects of bromine and methyl are identical. Such polar substituent effects are quite large at the α′-position of an α-bromo ketone, leading to the conclusion that the carbonyl group is much better than the methylene group in transmitting polar effects.Rate enhancements caused by α-bromine substituents are largely entropic in origin and rates correlate well with ionization constants of α-bromo acids. These results are interpreted as indicative of an enolate-like transition state for acetate-catalyzed enolization.

The decomposition mechanism for TDO in aqueous solution within 25–95 °C temperature range

2019 ◽  
Vol 731 ◽  
pp. 136603
Author(s):  
Jianzhong Shao ◽  
Xiaoyun Liu ◽  
Sergei V. Makarov ◽  
Kemei Pei
Keyword(s):  
Aqueous Solution ◽  
Decomposition Mechanism ◽  
Temperature Range

Inerte Amminkomplexe als mehrwertige Kationsäuren in wäßriger Lösung / Inert Ammine Complexes as Multivalent Cationic Acids in Aqueous Solution

1980 ◽  
Vol 35 (9) ◽  
pp. 1096-1103 ◽  
Author(s):  
Matthias Kretschmer ◽  
Lutwin Labouvie ◽  
Karl-W. Quirin ◽  
Helmut Wiehn ◽  
Ludwig Heck
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Spectrophotometric Method ◽  
Complex Cation ◽  
Aqua Ligand ◽  
Second Step ◽  
Acidity Constants ◽  
Ammine Complexes ◽  
Temperature Variations ◽  
Enthalpy Changes

Acidity constants of ammine complexes of tetravalent platinum in aqueous solutions have been determined by a spectrophotometric method at very low ionic strengths and extrapolated to zero ionic strength. Temperature variations of pK-values (25 °C and 50 °C) yield thermodynamic parameters for two successive deprotonation steps of hexaammineplatinum(IV), pentaamminechloroplatinum(IV), and tris(ethylenediamine)pla- tinum(IV) complexes and for the deprotonation of pentaammineaquacobalt(III) ion.The enthalpy changes for the first and second steps are similar and range from 50 to 75 kJ/mole while for the aqua ligand of Co(III) 33 kJ/mole are found. The very large dif­ference in the entropy changes (about 70 to 80 J/K mole for the first step and -10 to + 20 J/K mole for the second step) is interpreted by a model of solvation change. The primary hydration sphere of strongly oriented and immobilized water dipoles around the highly charged complex cation is transformed to a hydrogen-bonded solvation sheath when the electric field of the complex is weakened upon release of the first proton.

Substituent effects on the binding of phenols to cyclodextrins in aqueous solution

1989 ◽  
Vol 93 (18) ◽  
pp. 6863-6867 ◽  
Author(s):  
Gary L. Bertrand ◽  
James R. Faulkner ◽  
Soon M. Han ◽  
Daniel W. Armstrong
Keyword(s):  
Aqueous Solution ◽  
Substituent Effects

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

1983 ◽  
Vol 61 (1) ◽  
pp. 109-115 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Steric Effects ◽  
Slow Exchange ◽  
Conformational Properties ◽  
Derivatives Of ◽  
Ring Conformations ◽  
Twist Boat

The conformational properties of 2-alkyl (Me, Et, i-Pr, and t-Bu) and 2-phenyl derivatives of 1,3-dioxa-5,6-benzocycloheptene (1) were studied by 13C dnmr. Analysis of slow exchange spectra at 100.6 MHz indicates that all derivatives except tert-butyl exist in an equilibrium of chair (major) and twist-boat (minor) conformations. Substituent effects on the position of the equilibrium are rationalized in terms of steric effects.

Sign in / Sign up

Export Citation Format

Share Document