Para-Hydroxy benzoate

Perhaps the most accurate calculations performed to date are the MP2, LMP2, and LCCSD(TO) calculations on chorismate mutase (CM) and para hydroxy-benzoate-hydroxylase (PHBH) (the L in the acronyms indicates that local approximations were used, and TO is an approximate triples correction).41,42 These are coupled-cluster calculations that account for the effects of conformational fluctuations through an averaging over multiple pathways (16 for CM and 10 for PHBH). Initial structures were sampled from semiempirical QM/MM dynamics, using B3LYP/MM optimized reaction pathways. 

Class A FPMOs Mechanism and Structure Para-hydroxy Benzoate Hydroxylase (PHBH)... 

Heating a phenol ester in the presence of Nafion-H gave good yields of the hydroxy phenyl ketone.This Fries rearrangement gave a mixture of the ortho and para hydroxy compounds in a 1 2-2.5 ratio (Eqn. 22.19). A study of the rearrangement of phenyl benzoate over a number of solid acid catalysts indicated that Nafion-H was more effective than montmorilIonite or amorphous aluminum silicate for this reaction. " ... 

PhotoFries Rearrangement Of Poly (4-vinyl 3 -methoxv phenvl benzoate). Unit structures obtained in this reaction are those of the poly (4-vinyl 2 -hydroxy 4 -methoxy benzophenone) (Poly-5) and poly (4-vinyl 4 -hydroxy 2 -methoxy benzophenone) described in Figure II. For spectroscopic caracteristies we have compared the para-hydroxy derivative to poly (4-vinyl 2, 4 -dimethoxy ben-zophenone)(Poly-10) which is an intermediary in the synthesis of Poly-5 (13). Here too, absorption of the reaction products in the range of 100-360 nm were sufficient to estimate the ortho/para rearrangements ratio. The ultraviolet caracteristies of Poly-7, Poly-5, Poly-10 and results of irradiations of Poly-7 are listed in Tables VIII and IX. In the same conditions of irradiations, ortho/para ratio and yields are smaller than the values obtained in the case of Poly-6. But, as in the previous case, benzophenones are obtained very rapidly and the ortho product formation is greater than the para one. It is thus possible to consider poly (4-vinyl phenyl benzoates) as U.V. protectors. 

Unmodified BEA zeolite, on the other hand, shows the highest activity in the acylation of phenol wifh benzoic anhydride. Phenyl benzoate (PB) is the main product (61% yield), accompanied by C-acylated products (35%), with an interesting para-selectivity (ortho/para = 0.48). When the reaction time is increased from 4 to 20 h, an increase in para-hydroxy-benzophenone yield (from 11% to 23%) fogefher wifh a decrease in PB yield (from 79% to 64%) is observed however, a small increase in the orf/zo-hydroxybenzophenone yield (from 9% to 10%) cannof be avoided. The acfivify of the catalyst, together with its selectivity, does not distinctly decrease when the catalyst is used from fresh to firsf recycle. 

Only para coupling was observed during the alkaline ferricyanide oxidation of 4-hydroxy-3-(3-hydroxybenzoyl)benzoic acid. 7-Hydroxy-9-oxoxanthene-2-carboxylic acid (515) was obtained in 21% overall yield from methyl 4-hydroxybenzoate (78JCS(P1)876). The synthesis utilizes a photochemical Fries rearrangement of methyl 4-(3-methoxybenzoyloxy)benzoate to prepare the benzophenone (514 Scheme 189). A similar route was used to prepare 2-hydroxy-2 -methoxybenzophenones, which undergo intramolecular cyclization with loss of methanol on treatment with base. 

Aromatic carboxylic acids produce intense molecular ion peaks. The most important fragmentation pathway involves loss of OH to form the CeHsC O" (miz = 105), followed by loss of CO to form the ion (mIz = 77). In the mass spectrum of para-anisic acid (Fig. 8.71), loss of OH gives rise to a peak at miz =135. Further loss of CO from this ion gives rise to a peak at miz =107. Benzoic acids bearing ortho alkyl, hydroxy, or amino substituents undergo loss of water through a rearrangement reaction similar to that observed for orffto-substituted benzoate esters, as illustrated at the end of Section 8.8R. 

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