Preparation, Vibration and Electronic Spectral Studies of Substituted 1,4-quinones

Abstract

p-Quinones are a group of compounds which played a vital role in biological processes through their redox system in the respiratory cycles and blood. The chemistry of p-quinones including their preparation, reactions and different physicochemical properties were dealt with in chapter one of this thesis. Fifteen compounds of the type 2-amino-1,4-naphthoquinone, 2-hydroxy-3-amino-1,4-naphthoquinone and 2,5-diamino-1,4-benzoquinone were prepared in this work. The compounds were prepared according to a well established literature methods. The identities of the prepared compounds were confirmed by infrared, ultraviolet-visible spectral analysis and chromatographic examination. Mechanisms of the reactions and the appropriate retro synthetic analysis were given and discussed in chapter two. Detailed infrared examination of the target compounds was given and the functional groups were assigned to the proper absorption bands. Special emphasis was put upon the carbonyl group stretching vibration. In follow up the structure from simple p-benzoquinone which reveals the presence of one sharp carbonyl group at 1633 cm-1 to the more complicated unsubstituted naphthoquinones, a variations in the number of peaks and their positions were noticed. The introduction of a wide range of amines at position 2 of the quinoid ring cause some shift in the position of this absorption. The parent quinones, intermediate amines and the final compounds were scanned in the full range of UV-visible range, 200-800 nm in ethanol and in presence of both acids and bases. Attempts to locate all the types of E, K, B and R bands were carried out. Certain difficulties were encountered in assigning different absorbances and transitions whether those of ET or LE in both of the benzenoid and quinoid bands. An electron transfer band was noticeably for the benzenoid ring at 240-250nm and that of the quinoid ring was observed at 275nm