97  US 7,511,179 B2  98  (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 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.  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.  (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:  (R 2 =0.9224) was obtained.  (pKa)~0.0442•L\.H+6.8613  (Equation 4)  TABLE2  Fluorine-containing compound  having OH group  Model structure  (1)  (2)  L\.H  pKa  qC(CC;);OH  F  H  H  ’d-C(CC;);OH  60.5  9.8  59.5  10.2  40.4  9.0  29.9  8.3 