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(2) (Measurement ofpKa Value ofVarious Fluorine-contain› ing Compounds Having OH Group) 

Measurement of pKa Value of Cyclopentene Derivative Hav› ing -C(CF 3)2OH Group 

In a water/acetone mixture (10/15 ml) solution was put 0.4045 g of the above-mentioned cyclopentene derivative, followed by stirring at room temperature. After it was con- firmed that the solution became homogeneous, titration was carried out with about 0.2 mol/liter NaOH solution. A titra› tion curve was obtained by adding a NaOH solution dropwise in increments of0.15 ml and recording a pH value at every addition. An equivalence point was determined by an inflec› tion point (maximum differential value of titration curve=dpH/dml) of the titration curve. In this case, the equivalence point was 8.0 ml. A pH value at 4.0 ml which was a half of the equivalence point was read from the titration curve and was found to be 11.12. From a titration curve of water/acetone solution and aqueous solution which had been measured previously as a blank solution, a difference in a pH value derived from an electric potential difference between the solutions at titration of 4.0 ml was 1.50. Therefore from 11.12-1.50=9 .62, a pKa value of this norbomene derivative was determined as 9.62. 

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In the case of titration of 0.8104 g of cyclopentene deriva› tive by the same procedures as above, an equivalence point was 16.4 ml and a half of equivalence point was 8.4 ml. A pH value at a half of the equivalence point was 11.14. A differ- ence in a pH value between the both solutions at 8.4 ml was 1.19, and from 11.14-1.19=9.95, a pKa value of the cyclo› pentene derivative was determined as 9.95. 

In the case of titration of0.9812 g of cyclopentene deriva› tive by the same procedures as above, an equivalence point thereof was 18.95 ml andahalfof equivalence point was 9.48 ml. A pH value at this time was 11.03. A difference in a pH value between the both solutions at 9 .48 ml was 1.17, and from 11.03-1.17=9.86, a pKa value of the cyclopentene derivative was determined as 9.86. 

From those experiments carried out three times, a pKa value of the cyclopentene derivative was determined as 9.8. 

With respect to the various fluorine-containing compounds having OH group shown in Table 2, a pKa value was mea› sured by the same procedures as above. The results are shown in Table 2. 

(3) Relation Between llH and Actually Measured pKa 

With respect to the various fluorine-containing compounds having OH group shown in Table 2, FIG. 1 is a graph in which calculated AH and actually measured pKa are plotted in an abscissa and an ordinate, respectively. As shown in FIG. 1, it was found that a good proportional relation is exhibited. 

From the graph, an equation: 

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(R 2 =0.9224) was obtained. 

