Thermodynamics of ionization of 2,4- and 2,5-dinitrophenol in dimethylsulfoxide

1980 ◽  
Vol 58 (10) ◽  
pp. 970-973 ◽  
Author(s):  
Kok-Siong Siow ◽  
Kok-Peng Ang
Keyword(s):  
Thermodynamic Functions ◽  
Solvent Effects ◽  
Ionization Constants ◽  
Conductance Method ◽  
Thermodynamics Of Ionization

Ionization constants of 2,4- and 2,5-dinitrophenol in dimethylsulfoxide were measured by the conductance method at five temperatures ranging from 20 to 40 °C. The ionization constants of 2,4-dinitrophenol are much larger than those of 2,5-dinitrophenol, and in both cases they increase with temperature. The thermodynamic functions of ionization are discussed in terms of Hepler's theory for substituent and solvent effects. The ionization of phenols in dimethylsulfoxide is controlled by the enthalpy factor, both internal and environmental, which is in contrast to the entropy-controlled process in water.

Thermodynamics of ionization of trans-crotonic and adipic acids in water; the silver – silver adipate electrode

1980 ◽  
Vol 58 (4) ◽  
pp. 323-327 ◽  
Author(s):  
Upendra Nath Dash ◽  
Uttam Kumar Nayak
Keyword(s):  
Adipic Acid ◽  
Silver Chloride ◽  
Ionization Constants ◽  
Thermodynamic Quantities ◽  
Liquid Junction ◽  
Different Temperatures ◽  
Heat Capacity Changes ◽  
Silver Silver ◽  
Silver Silver Chloride ◽  
Thermodynamics Of Ionization

The ionization constant, K, of trans-crotonic acid, and the first and second ionization constants, K1 and K2, of adipic acid have been determined in water at seven different temperatures ranging from 15 to 45 °C with the help of the cells without liquid junction using silver – silver chloride and quinhydrone electrodes. The variations of pK, pK1, and pK2 with temperature have been expressed by the equations[Formula: see text]and[Formula: see text]From the temperature coefficient of the ionization constants, the standard enthalpy, entropy, Gibbs energy, and heat capacity changes of the corresponding dissociation processes have been calculated. Using the values of ionization constants of adipic acid, the standard potential of the Ag(s)/Ag2Ad(s)/Ad2− electrode, and the related standard thermodynamic quantities for the electrode process[Formula: see text]have been calculated in water at those temperatures.

Determination of thermodynamic functions by means of infrared spectroscopy. The accuracy in -ΔH determination; Formation of complexes phenol-pyridine and its homologues

1979 ◽  
Vol 44 (1) ◽  
pp. 148-156 ◽  
Author(s):  
Václav Šára ◽  
Jaromír Moravec ◽  
Milan Horák
Keyword(s):  
Infrared Spectroscopy ◽  
Thermodynamic Functions ◽  
Ionization Constants ◽  
Experimental Conditions ◽  
Pyridine Bases ◽  
Methyl Derivatives ◽  
Pyridinic Nitrogen ◽  
Influence Of Substituents ◽  
Formation Of Complexes

Values of thermodynamic functions -ΔH, -ΔG, and -ΔS of the complex formation between molecules of pyridine (and its methyl derivatives) and phenol in CCl4 solutions were determined using infrared spectroscopy. After optimalizing experimental conditions the error in -ΔH determination does not exceed 0.2%; this accuracy is sufficiently high to investigate the influence of substituents on the pyridinic nitrogen basicity. The values of -ΔH determined in this way correlate linearly with values of ionization constants of pyridine bases.

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.

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