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The Fries rearrangement is an organic reaction used to convert a phenyl ester to a hydroxy aryl ketone using a Lewis acid catalyst and Brønsted acid work-up. In this reaction, an acyl group belonging to phenol ester migrates to the aryl ring either in the ortho or para position, depending on the reaction temperature and solvent.
- What Is The Fries Rearrangement reaction?
- Fries Rearrangement Mechanism
- Limitations of Fries Rearrangement
Fries Rearrangement is an organic rearrangement reaction in which an aryl ester is transformed into a hydroxy aryl ketone with the help of a Lewis acidcatalyst and an aqueous acid.In this reaction, an acyl group belonging to the phenolic ester migrates to the aryl ring.It is important to note that Fries rearrangement is ortho and para selective, i.e. the acyl group attaches itself at the ortho or para positions of the aryl ring.The selectivity of the reaction can be directed by modifying the reaction conditions (such as the temperature under which the reaction is conducted, or the solvent used in the reaction).Initially, the carbonyl oxygen belonging to the acyl group forms a complex with the Lewis acid catalyst (usually AlCl3). The formation of the complex with the carbonyl oxygen is favoured over the complexation of the phenolic oxygen since the carbonyl oxygen is richer in electrons and is, therefore, a better Lewis base. Now, the bond between the phe...
The key limitations of Fries rearrangement are listed below. 1. Owing to its relatively harsh reaction conditions, only esters with relatively stable acyl components can be used in this reaction. 2. Low yields are obtained when heavily substituted acyl components exist. 3. The presence of deactivating or meta-directing groups on the aromatic ring r...
Fries rearrangement. The Fries rearrangement, named for the German chemist Karl Theophil Fries, is a rearrangement reaction of a phenolic ester to a hydroxy aryl ketone by catalysis of Lewis acids. [1][2][3][4] It involves migration of an acyl group of phenol ester to the aryl ring. The reaction is ortho and para selective and one of the two ...
Mechanism of the Fries Rearrangement. The reaction is catalyzed by Brønsted or Lewis acids such as HF, AlCl 3, BF 3, TiCl 4 or SnCl 4. The acids are used in excess of the stoichiometric amount, especially the Lewis acids, since they form complexes with both the starting materials and products. The complex can dissociate to form an acylium ion.
This video explains what is Fries rearrangement. The rearrangement involves the phenolic ester to a hydroxy aryl ketone using Lewis acids. The lewis acid is ...
- 6 min
- 1634
- One Chemistry
The mechanism for a Fries rearrangement which is used to convert a phenyl ester to an ortho- and para-hydroxy aryl ketone using a Lewis acid catalyst and aci...
- 3 min
- 1890
- Organic Mechanisms
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What is Fries rearrangement?
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How does Fries rearrange aryl esters?
Which acyl group migrates to the aryl ring in Fries rearrangement?
Why is Photo-Fries rearrangement not used in commercial production?
Jan 23, 2023 · Herein, the first mechanochemical Fries rearrangement for the industrially important synthesis of para-hydroxyacetophenone, inside a ball mill and a twin-screw extruder, is presented. Our approach leads to a yield of 62 % in as little as 90 minutes while liquid-assisted grinding can shift the isomer ratio resulting in an excess of the desired para -product.
