Q2 GIBBS, WILLIAMS, AND PRATT. 
of this form of tautomerism.” The exact coincidence of the bands in 
different compounds, characteristic of this condition, is not material since 
their position may be altered by the character of adjacent atoms or 
groups. An increase in the mass of the molecule causes the oscillation 
frequency to decrease and the band is shifted toward the red. Thus, the 
nitrogen atom of aniline and the carboxyl group of the hydroxybenzoic 
acids shift this band, and an important characteristic in its identification 
is the shifting toward the red which is produced in the presence of 
akalies. 
The spectrum of benzoic acid” shows only general absorption, o- and 
m-hydroxy benzoic acids” give a strong absorption band heading about 
300 “# while the para compound shows no corresponding band. The three 
eresols show the characteristic band heading about 275 uu and the three 
dihydroxy phenols also exhibit the same uniformity. The amino phenols 
are tautomeric in the same way as are the phenols. p-amino phenol, the 
only one investigated by Baly and Eubank, has the characteristic band 
heading about 300 uz. 
That this tautomerism is present in all the phenols is supported 
by their chemical behavior, in fact the greater the number of 
hydroxyl groups, the greater.the chemical activity. A notable 
exception seems to be p-hydroxy benzoic acid. This compound, 
as has been stated, shows no absorption band characteristic of 
the labile hydrogen, and the hydroxyl group in the para position 
behaves like a positive radicle decreasing the hydrogen ioniza- 
tion of benzoic acid. 
Baly and Eubank™ point out that the internal motions of the benzene 
ring are less disturbed by the substitution of two groups in the para 
position than in either the ortho or the meta. In every case which they 
examined, the para compounds showed strong evidence of being more 
symmetrical than the other two isomers, that is, the para compounds gave 
an absorption much more closely related to the parent substance benzene, 
than did the ortho or meta. 
The oxidation of the phenols is much more easily effected when 
the hydrogen, para to the phenol group, is not fixed. This is 
especially typical in the case of the three hydroxy acids, the 
ortho and meta being comparatively easily effected, while the 
para acid is not changed by the sunlight in presence of oxygen, 
or at least the rate of reaction is so slow as to be negligible. 
In the case of p-cresol, while the para oxidation is not possible, 
* Baly and Collie, Journ. Chem. Soc. London (1905), 87, 1839. 
“ Hartley and Huntington, Phil. Trans. (1879), 170, 1257. 
“ Hartley, Journ. Chem. Soc. London (1888), 53, 641. 
* Derick, Journ. Am. Chem. Soc. (1912), 34, 79. 
“ Journ. Chem. Soc. London (1905), 87, 1855. 
