Resorcylic acid, decarboxylation

Since the nitration of resorcinol by the conventional method for phenols (i.e. sulphonation followed by the action of nitric acid) yields a trinitro derivative, two other methods for the preparation of dinitroresorcinol are possible, viz. oxidation of dinitrosorcsorcinol or nitration of resorcylic acid followed by decarboxylation. 

Hemmelmayer [28] presented the nitration of resorcylic acid and its subsequent decarboxylation by the following reactions ... 

The data for this solvent were not used to calculate the parameters in Table 54. Similarly the data for decarboxylation of oxanilic acid in anisole were not used for the AH -AS correlation. With the reported AH value of 32.6 kcal.mole , the entropy of activation is calculated to be 3.59 0.03 eu compared to the reported value of 11.1 eu. In the decarboxylation of malonic acid, the data obtained with pyridine and ) -mercaptopropionic acid solvents deviated considerably from the plots and were not included in the correlation. The data for malonic acid decarboxylation appeared to be best correlated by two lines. One line was described by the following solvents acids, phenols, nitro-aromatics, benzaldehyde, and the melt the other line involved amines, alcohols, dimethylsulfoxide and triethyl phosphate. The latter line was not as well defined as the former. However, it was our intention to correlate as many solvents as possible with a minimum number of lines. The data for decarboxylation of malonic acid in water and in benzyl alcohol fell between these two lines and were not included in either correlation. The data for decarboxylation of benzylmalonic acid also appeared to be best correlated with two lines. One line was defined by the cresols, acids and the melt, while the other line was defined by the amines. Decarboxylation of cinnamalmalonic acid was correlated by two lines as indicated in Table 54. Similarly j8-resorcylic acid was correlated by two lines. The separation of data into parallel lines is presumably due to multiple solvation mechanisms . In support of this interpretation it is seen that when two lines are observed, acids fall into one line and amines into the other. It is not unexpected that the solvation mechanisms for these two classes of solvents would differ. It is interesting to note that all of the nitrogen containing acids are correlated reasonably well with one line for both basic and acidic solvents. Also the AHq values fall in a rather narrow range for all of the acids. From the values of p in Table 54, there appears to be little correlation between this parameter and the melting point of the acids, contrary to prior reports " ... 

Bromoresorcinol may be similarly prepared from /3-resor-cylic acid [27]. To obtain 2-bromo- or 2-chloro-resorcinol, /3-resorcylic acid is successively nitrated and halogenated. The resulting product is then reduced, deaminated, and finally decarboxylated (H2O, 100 , 3hr) to give the desired compound [28]. 

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