The formation of Fries rearrangement by-products represents the main drawback affecting the melt synthesis of PC since these by-products present a significant light absorbance in the visible region and therefore produce discoloration in the final material.
0 ppm was ascribed to 1H of the linear Fries rearrangement products, while the signal at 8.
These conditions favor degradation reactions, yellowing, and sometimes branching of the product PC caused by Fries rearrangements by-products [8, 9].
4] (PPA) was found to be an efficient new reagent for probing the mechanism of acylation reactions and Fries rearrangement of acyloxy benzene derivatives and also the direct acylation reactions of phenol derivatives with Carboxylic acids.
In the same way we have investigated the effects of ortho, meta and para substituents on the acylation reactions of benzoic acid derivatives and also Fries rearrangement in PPA.
Keywords: Polyphosphoric acid (PPA), Acylation reactions, Fries rearrangement, Hydroxyaryl Ketones, Phenol derivatives.
Fries rearrangement is a synthetically useful reaction for the preparation of hydroxyaryl ketones, not only in laboratory but also in industrial processes .
In this work we probed the mechanism of Fries rearrangement of acyloxy benzene derivatives based on the mechanism which suggested by H.
In addition, we optimized the best conditions to achieve the Fries rearrangement.
In the same way, we investigated the effects of ortho- meta- and para- substituents on acylation reactions of benzoic acid derivatives and also Fries rearrangement in PPA (Scheme 2 and Tables 1, 2 and 3)
Therefore, the Fries rearrangement mechanism may be in agreement with the free acylinium ion (Intermolecular rearrangement) mechanism and not related to the [pi]-cmplex (Intermolecular rearrangement) mechanism.