Qualitative Prediction of Reaction Rates Using Transition State Theory, Solvent Effects and Activation Parameters: A Review

Transition State Theory (TST), also known as Activated Complex Theory, provides an important theoretical framework for understanding and qualitatively predicting the rates of chemical reactions. The theory proposes that reactant molecules undergo transformation through a high-energy transition state or activated complex before forming products. The rate of a reaction is strongly related to the Gibbs free energy of activation (ΔG‡), while the enthalpy of activation (ΔH‡) and entropy of activation (ΔS‡) provide additional information about the nature and organization of the transition state. The uploaded article emphasizes the application of these concepts to organic reactions and mixed aqueous–organic solvent systems. It also discusses the Hughes–Ingold approach, hydrogen bonding, ion-solvating power of solvents, and the role of activation parameters in interpreting reaction mechanisms. Solvent polarity, solvation, molecular structure, substituent effects, and temperature can significantly influence the stability of reactants, intermediates, and transition states, thereby modifying reaction rates. The review demonstrates that combining Transition State Theory with solvent effects and activation parameters provides a useful qualitative approach for understanding reaction mechanisms and comparing relative reaction rates.

Transition State Theory Activated Complex, Reaction Rate, Gibbs Free Energy of Activation, Enthalpy of Activation

1. Seliverstova T S, Marina Kushner, Matusevich L G. (2020). Kinetics and mechanism of hydrolysis of Benzyl Ether bond in aqueous-organic media. Russian J of Physical Chemistry A. Vol-94: 310-316. [Google Scholar] [Crossref]

2. 2.Magda F Fathalla,Yassir R. Elmarassi.(2019). The reaction of 2-chloroquinoxaline with piperidine in DMSO-H2O and DMF- H2O mixture. Kinetic and solvent effect. Journal of solution chemistry. Vol. 48:1287-1308,. [Google Scholar] [Crossref]

3. Singh A K. (2026). Organic Reaction in Mixed Aqueous Solvents and their Kinetics. International journal of Research and Scientific Innovation (IJRSI) ISSN No.2321-2705.DOI:10.51244/IJRSI. VOL VIII. Issue-VII. July 2026. PP1747-1753. [Google Scholar] [Crossref]

4. Keith J. Laidler, & John H. Meiser. (1999). Physical Chemistry. Houghton Mifflin. [Google Scholar] [Crossref]

5. Kenneth A. Connors. (1990). Chemical Kinetics: The Study of Reaction Rates in Solution. VCH Publishers. [Google Scholar] [Crossref]

6. F. A. Carey, & Richard J. Sundberg. (2007). Advanced Organic Chemistry, Part A: Structure and Mechanisms (5th ed.). Springer. [Google Scholar] [Crossref]

7. Jerry March. (1992). Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (4th ed.). John Wiley & Sons. [Google Scholar] [Crossref]

8. Isaac Lowry, & K. S. Richardson. (1987). Mechanism and Theory in Organic Chemistry (3rd ed.). Harper & Row. [Google Scholar] [Crossref]

9. Christopher G. Swain, Christopher B. Scott, & Robert W. Taft. Studies on solvent effects and transition state stabilization in organic reactions. Journal of the American Chemical Society. [Google Scholar] [Crossref]

10. Henry Eyring. (1935). "The Activated Complex in Chemical Reactions." Journal of Chemical Physics, 3, 107–115. [Google Scholar] [Crossref]

11. Meredith Gwynne Evans, & Michael Polanyi. (1935). "Some Applications of the Transition State Method to the Calculation of Reaction Velocities." Transactions of the Faraday Society, 31, 875–894. [Google Scholar] [Crossref]

12. Cyril Norman Hinshelwood. (1940). The Kinetics of Chemical Change. Oxford University Press. [Google Scholar] [Crossref]

13. Kenneth B. Wiberg. (1964). Physical Organic Chemistry. John Wiley & Sons. [Google Scholar] [Crossref]

14. 14 John McMurry. (2021). Organic Chemistry (10th ed.). Cengage Learning. [Google Scholar] [Crossref]

15. Thomas H. Lowry, & Kathleen Schueller Richardson. (1987). Mechanism and Theory in Organic Chemistry (3rd ed.). Harper & Row. [Google Scholar] [Crossref]

16. 16. Singh AK & LK. TIWARI . (2020) “Study of Solvent effect of Protic solvent on Solvolysis of Hexanoate ester and Activation parameters.” Asian journal of Research in Chemistry, ISSN 0974-4150, 13(3), pp 216-218. DOI: 10.5958/0974-4150.2020.00041.3 [Google Scholar] [Crossref]

17. Singh A K. (2019). Kinetics and solvent effect on activation parameter of aquo-propanol solvent system for acid catalyzed solvolysis of propyl formate. International Journal of Chemical Science ISSN:2523-2843 ,Vol-3, Issue-4, July, pp85-88 [Google Scholar] [Crossref]

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