Thermodynamic analysis of the ionization of ortho and para toluic acids : influence of the medium on the hyperconjugative and steric effects |
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| Affiliation: | 1. Department of Chemistry, Geethanjali College of Engineering and Technology, Cheeryal 501301, India;2. Department of Pharmacy, School of Health Science, University of Kwazulu Natal, Durban, South Africa;3. Department of Chemistry, Osmania University, Hyderabad 500007, India;1. Department of Chemistry and Pharmacy, University of Sofia, Sofia 1164, Bulgaria;2. Center for Computational Quantum Chemistry, University of Georgia, Athens, GA 30602, United States;1. School of Metallurgy and Environment, Central South University, Changsha 410083, China;2. Department of Dermatology, Second Xiangya Hospital, Central South University, Changsha 410011, China;3. College of Environmental Science and Engineering and Key Laboratory of Environmental Biology and Pollution Control (Ministry of Education), Hunan University, Changsha 410082, China;4. Institute of Big Data and Internet Innovation, Hunan University of Technology and Business, Changsha 410205, China;5. Center of Research Excellence in Renewable Energy and Power Systems, Center of Excellence in Desalination Technology, Department of Mechanical Engineering, King Abdulaziz University, Jeddah 21589, Saudi Arabia |
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| Abstract: | The hyperconjugative effect of the methyl group in the para and ortho position of the benzene ring is studied as a function of the medium. The ionization and solution enthalpies of ortho and para toluic acids have been measured in H2O/DMSO mixtures. A study of the ortho effects by means of the linear combination of the ordinary polar, proximity polar and steric effects has also been performed.The methyl group both in ortho and para position seems to be forced out by the benzene ring at Xdmso= 0.5 mole fraction with a consequent decrease of hyperconjugation effect. A study of enthalpic and entropic contributions to substituent and reaction constants and the proton transfer process from ortho and para derivatives to benzoic acid, compared with the same process in the gaseous phase are also presented. |
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