Quinone studies

Abstract

CHAPTER I First chapter contains a brief review on the oxidation-reduction potentials of quinones. Various factors like resonance energy, substituents, solvents and pH of the medium that influence the oxidation-reduction potentials of quinones are discussed. Methods of determining oxidation-reduction potentials have also been surveyed briefly. An attempt has been made to explain the cause of difference in the potentials of ortho and para quinones. It is hoped that this chapter will be useful as background material for later chapters. CHAPTER II A new approach for synthesizing phenanthrene derivatives has been explored. The structures of unexpected products obtained by the reaction of phenacyl bromide and phenylmagnesium bromide have been determined. Syntheses of 3-alkyl substituted phenanthrenes by a new sequence is described. CHAPTER III Half-wave potentials of 3-substituted phenanthrenequinones have been determined in five buffer solutions having different pH values. It has been shown that the half-wave potentials bear a linear relationship with Hammett's ? constants. CHAPTER IV Detailed kinetics of chromic acid oxidation of phenanthrene and 3-substituted phenanthrenes to the corresponding quinones has been described. The rate expression obtained is as follows: Phenanthrene + HCrO?? ? Quinone It is found that electron-donating groups increase the rate and electron-withdrawing groups decrease it. It is found that the rate of oxidation follows Hammett equation. This is the first successful attempt, as far as we are aware, to correlate the rates of reaction at 9,10-positions of phenanthrene with Hammett's ? constants. CHAPTER V Structures assigned in literature to the compounds obtained from the reaction of p-benzoquinone, pyridine and carboxylic acids have been shown to be incorrect. On the basis of spectroscopic evidence, it has been shown that the compounds are charge-transfer complexes between the quinone and pyridinium salts of carboxylic acids.