Of phthalamic acid

Many sigmoid rate curves have been reported. A typical example is provided by the hydrolysis of phthalamic acid. ... 

For an example, see 10-9.) When this happens internally, we have an example of a neighboring-group mechanism at a carbonyl carbon. For example, the hydrolysis of phthalamic acid (77) takes place as follows ... 

The pH-rate constant profile for hydrolysis of phthalamic acid showed participation by the undissociated carboxyl group, and an anhydride intermediate was detected (Bender, 1957 Bender et al., 1958b). Hydrolysis was 10 times faster than in the case of p-carboxybenzamide. A four-center mechanism [58] was postulated. 

A solution of 30 g. (0.165 mole) of ammonium phthalamate in 30 ml. of cold water is treated with 20 ml. of concentrated hydrochloric acid. The solid formed is collected by filtration, and the white paste obtained is washed with cold water until free of chloride. The yield is 22 g. (81%). The phthalamic acid melts at 149 with loss of water, resolidifies at about 155 , and remelts at 231 . This represents conversion of phthalamic acid to phthalimide (m.p. 231 ). 

The mechanism of the intramolecular general acid catalysis of the oxygen esters has not been established since the possible formation of anhydride intermediates has not been thoroughly investigated. The hydrolysis of phthalamic acid has been shown to proceed through an anhydride intermediate, detected by double labeling experiments (Bender et al., 1958a), as does the aminolysis of succinic acid. In these cases, the reaction may involve either a four-center path, symbolised by 40, or involve prior protonation followed by intermolecular attack by the carboxylate anion (41). 

Aminopropyltrimethoxysilane coupling of phthalamic acid to silica particles on a quartz crystal microbalance Uranyl nitrate [12]... 

The hydrolysis rate of phthalamic acid is 105 times faster than that of benzamide. Formation of a phthalic anhydride intermediate has been demonstrated in C13- and 018-labeling experiments (13). These results and the degradation data are consistent with the previously proposed mechanism of intramolecular displacement of the protonated amide moiety by the carboxylate anion (7,13,14). 

Detection of an intermediate by double labelling is well exemplified in the hydrolysis of phthalamic acid to phthalic acid [49]. One mechanism involves phthahc anhydride as an intermediate and this may be checked by labelling the amide carbon with C and the water with 0 (Eqn. 68). 

It is now evident that the acmal rate enhancement due to intramolecular carboxylic-acid-assisted hydrolysis of phthalamic acid is °o, because for the hydrolysis of benzamide under identical experimental conditions is nearly zero. However, if one compares the for the hydrolysis of phthalamic acid... 

Bender, M.L. General acid-base catalysis in the intramolecnlar hydrolysis of phthalamic acid. J. Am. Chem. Soc. 1957, 79, 1258-1259. 

The hydrolysis and alkylaminolysis products of phthalimide are phthalamic acid and A-substituted phthalamide, respectively, and these products show an insignificant absorption at 300 nm. The values of molar extinction coefficients of phthalamic acid and phthalic acids are same as 40 Af cm- at 300 nm. ° Thus, the calculated value of A for the reaction mixtures containing 0.50-M trimeth-ylamine at pH 10.95 (A 0.0, Table 7.2) is plausible in view of insignificant absorption of phthalamic acid at 300 mn. 

Blackburn, R.A.M., Capon, B., McRitchie, A.C. The mechanism of hydrolysis of phthalamic acid and N-phenylphthalamic acid the spectrophotometric detection of phthaUc anhydride as an intermediate. Bioorg. Chem. Wll, 6, 71-78. 

The work at the University of Wyoming was supported by the National Science Foundation through an EPSCoR-ADP grant T e work at the University of California at Berkeley was supported by the Office of Naval Research. Paul Walton is acknowledged for elucidating certain aspects of the solution phase behavior of phthalamic acid binding to U02. ... 

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