Intramolecular Interaction between Hydroxyl Group and π-Electrons. VI. Electronic Effect on the Interaction in ω-Arylalkanols

Publisher Website
Google Scholar
Abstract
The electronic effect on the intramolecular interaction between the hydroxyl group and the π-electrons of the benzene nucleus was studied with various ω-aryl-alkanols. In 2-arylethanols, introduction of an electron-releasing group into the benzene nucleus gives rise to the shift of the νO–H absorption maxima to a lower wave number and to greater integrated intensities of the band due to the interacting form, and introduction of an electron-attracting group to a higher wave number and smaller integrated intensities. However, the wave number of the band due to the interacting form is not affected by the position of the substituent, as far as the substituent is the same. Thus, the structure represented by IX is favored. On the other hand, a compound with an electron-releasing group in the meta position always shows greater integrated intensities of the band due to the interacting form than the para-substituted isomer and this fact saves structure VIII from entire rejection. Hence, the authors tentatively assign structure IX as the most favorable with participation of structure VIII to some extent. In 3-arylpropanols the interaction is observed only in the compounds with an electron-releasing group and 3-(p-chloro-phenyl)-propanol shows the normal νO–H absorption for primary alcohols. The phenomenon that 3-arylpropanols show smaller interaction in spite of the appearance of the band due to the interacting form at a lower wave number is attributed to the unfavorable change in both energy and entropy. In 4-arylbutanol no interaction is observed, even though a strongly electron-donating group is introduced. Thus, as the authors predicted, it has been proved that the intramolecular interaction occurring in 2-phenylethanol is different in nature from that in benzyl alcohol.