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Acid Dissociation Constants, Enthalpy, Entropy and Gibbs Energy of Bedaquiline by UV-Metric Spectral and pH-Metric Analysis
- Source :
- Journal of Solution Chemistry. 50:315-339
- Publication Year :
- 2021
- Publisher :
- Springer Science and Business Media LLC, 2021.
-
Abstract
- Bedaquiline (trade name Sirturo) is an antibiotic used to treat pulmonary tuberculosis that is resistant to other antibiotics. The pH-spectrophotometric and pH-potentiometric titrations allowed the measurement of two near successive and one distant dissociation constants. The neutral bedaquiline LH molecule was able to protonate and dissociate in pure water to form soluble species L−, LH, $${\text{LH}}_{2}^{ + }$$ , $${\text{LH}}_{3}^{2 + }$$ and $${\text{LH}}_{4}^{3 + }$$ . In the pH range 2–7, three dissociation constants can be reliably estimated. REACTLAB (UV-metric spectral analysis) values are: $${\text{p}}K_{{{\text{a}}1}}^{T}$$ = 3.91(09), $${\text{p}}K_{{{\text{a}}2}}^{T}$$ = 4.58(12) and $${\text{p}}K_{{{\text{a3}}}}^{T}$$ = 5.26(07) at 25 °C and $${\text{p}}K_{{{\text{a}}1}}^{T}$$ = 3.61(30), $${\text{p}}K_{{{\text{a2}}}}^{T}$$ = 4.44(15) and $${\text{p}}K_{{{\text{a3}}}}^{T}$$ = 5.54(33) at 37 °C. ESAB (pH-metric analysis) values are: $${\text{p}}K_{{{\text{a}}1}}^{T}$$ = 3.21(39), $${\text{p}}K_{{{\text{a2}}}}^{T}$$ = 3.68(31) and $${\text{p}}K_{{{\text{a3}}}}^{T}$$ = 5.21(42) at 25 °C and $${\text{p}}K_{{{\text{a}}1}}^{T}$$ = 3.31(12), $${\text{p}}K_{{{\text{a2}}}}^{T}$$ = 3.67(15) and $${\text{p}}K_{{{\text{a3}}}}^{T}$$ = 5.73(08) at 37 °C. Molar enthalpy ΔH0, molar entropy ΔS0 and Gibbs energy ΔG0 were calculated from the spectra using the dependence of ln K on 1/T. The potentiometric data showed positive enthalpy ΔH0(pKa1) = 85.49 kJ·mol−1, ΔH0(pKa2) = 86.42 kJ·mol−1, and ΔH0(pKa3) = 65.84 kJ·mol−1 values and the dissociation reactions were endothermic. The entropy ΔS0 at 25 °C was positive for the three dissociation constants ΔS0(pKa1) = 217.47 J·K−1·mol−1, ΔS0(pKa2) = 204.87 J·K−1·mol−1, and ΔS0(pKa3) = 92.63 J·K−1·mol−1 at 25 °C and proved irreversible dissociation reactions.
- Subjects :
- Standard molar entropy
Chemistry
Enthalpy
Biophysics
02 engineering and technology
010402 general chemistry
01 natural sciences
Biochemistry
Acid dissociation constant
0104 chemical sciences
Gibbs free energy
Entropy (classical thermodynamics)
symbols.namesake
Crystallography
020401 chemical engineering
Pulmonary tuberculosis
symbols
Ph range
Spectral analysis
0204 chemical engineering
Physical and Theoretical Chemistry
Molecular Biology
Subjects
Details
- ISSN :
- 15728927 and 00959782
- Volume :
- 50
- Database :
- OpenAIRE
- Journal :
- Journal of Solution Chemistry
- Accession number :
- edsair.doi...........bee71c5ae7a5633c649c02dcc5cbc640