A Voltammetric Determination Of The Effect Of Hydrogen Bonds On Acids And Bases In Aprotic Solvents

Proton coupled electron transfer reaction(PCET)plays a crucial role in both biological and chemical reactions.The most typical pair of redox substances in PCET reactions is p-benzoquinone hydroquinone,and hydrogen bonding also has an important impact on the study of PCET reactions.This paper investigates the effect of hydrogen bonding on acidity and alka linity in proton inert solvents through the electrochemical reduction of p-benzo quinone and the oxidation of hydroquinone.The derivative of p-benzoquinone tetramethylbenzoquinone was used as an auxiliary study,and hydroquinone was selected as the proton donor to investigate their electrochemical behavior in acetonitrile.The solvent of both systems was acetonitrile;We also investigated the reduction process of p-benzoquinone using acetic acid,lactic acid,and trifluoroacetic acid as proton donors,as well as the influence of conjugated bases of diethylamine,triethanolamine,aniline,and acetic acid on the oxidation process of p-benzoquinone.We found that when a certain concentration of acid is added to the acetonitrile solution of p-benzoquinone,a new cathodic peak is formed,and the current of this new cathodic peak shows a good linear relationship with the concentration of the acid,The peak potential is determined by the pKa value of the acid and is independent of the concentration of benzoquin one.As the p Ka value of the acid increases,the new peak potential shifts in a positive direction;After adding a certain concentration of alkali to the solution of hydroquinone,a new oxidation peak will appear,and its new peak potential is determined by the p K_b value of the alkali.As the p K_b value of the alkali increases,the new peak potential also shifts in the positive direction;Subs equently,a certain concentration of hydrogen bonding reagents and different hydrogen bonding reagents of the same concentration were added to the reaction system.Analysis showed that the concentration of hydrogen bonding reagents was proportional to the displacement of new peaks,and the new peak potentials of compounds that could form hydrogen bonds moved in a positive direction after addition.The stronger the hydrogen bonding effect,the more changes in peak potentials and the greater the changes in acidity and alkalinity.A new electrochemical method has been established to study the effect of hydrogen bonding on acidity and alkalinity.So it is concluded that the formation of hydrogen bonds in non aqueous solvents helps to enhance the acidity of acids and weaken the alkalinity of bases.This study does not require the addition of any indicator or titrant,and the operation is simple with minimal sample usage,fast analysis speed,and accurate results.Finally,a brief discussion was conducted on the direction of further work.