1H NMR study of through‐bond and through‐space effects in the hetero‐association of pyridine with alkane diols

摘要: The 1H NMR titration method is used to investigate through-space and through-bond effects on the association of diols with pyridine in benzene. Alkan-1,n-diols (n goes from 2 10), DL meso isomers butan-2,3-, pentan-2,4- hexan-2,5-diols, two adamantane a bicyclo[2.2.2]octane diol are compared alkanols. –CH2OH groups tri- bicyclic compounds behave as if they were independent, limiting OH proton shifts (at very low concentration) both first second constants similar those primary alcohol. In contrast, alkane diols, n = 2–4, display unusually high shifts, ranging 1.0 1.5 ppm (2.1 ppm for one methyl-substituted diol). For these dissociation constant sum 1:1 pyridine: complex enhanced. This may be attributed small cooperative effects, implying intramolecular hydrogen bonding, n = 3 4, but n = 2 effect accounts most increase. Substituent interaction falls off sharply n = 5 practically negligible n = 10, which close first. A sterically hindered BiEDOT diol, 2,2′-bis{(3,4-ethylenedioxythienyl)-5-[3-(2,2,4,4-tetramethylpentan-3-ol)]} behaves like polycyclic compounds, C(t-Bu)2OH independent. Copyright © 2010 John Wiley & Sons, Ltd.