STRUCTURES AND PROPERTIES OF SUBSTITUTED PHENOLS

During the 160 years since the discovery of phenol, thousands of studies were conducted on halophenols, partly due to their significance in the theory of hydrogen bonding indeed their hydrogen bonding abilities can be varied nearly continuously over a wide pATj range from 10.2 to 0.4 - . 

Inspection of Table 11, which gathers the harmonic vibrational modes of both conformers with the corresponding potential energy distribution patterns, reveals that the trans voe is calculated at 3835.4 cm , which is almost identical to voe of phenol in Table 10, while its cis partner is red-shifted (as expected according to the theory of hydrogen bonding by cis-trans aa cm . This calculated value lies rather close 

In this regard, the more than two decades following the appearance of Pauling s work ° deserve to be recalled. Indeed, on the one hand, they were full of criticism of the earlier experimental results because it was believed that the higher frequency band appears more likely due to a trace of phenol impurity than to the presence of trans isomer and the new experiment demonstrated the ratio of the absorptions being much smaller and equal to 1/56 17.9 x 10 , which anyway is about three times larger than 

In 1958, it was verified experimentally that the cis-trans doublet could not be detected for 0-FC6H4OH the trans vqh band was suggested to be too weak to show up in IR experiments and cis-trans ou small ( 20 cm it is estimated 

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