Diols as hydrogen bond acids: ¹H NMR study of the hetero‐association of pyridine with sterically hindered EDOT diols

Abstract

The hetero‐association of pyridine with the cis and trans methyl‐3,4‐ethylenedioxy‐2‐[3‐(2,2,4,4‐tetramethylpentan‐ 3‐ol)]thiophenes (Me‐EDOT alcohols), 3,4‐ethylenedioxy‐2,5‐bis[3‐(2,2,4,4‐tetramethylpentan‐3‐ol)]thiophene (EDOT diol) and methyl‐3,4‐ethylenedioxy‐2,5‐bis[3‐(2,2,4,4‐tetramethylpentan‐3‐ol)]thiophene (Me‐EDOT diol) has been studied by 1H nuclear magnetic resonance (NMR) spectroscopy in benzene at 298 K. Self‐consistent association constants for the syn (S), anti‐syn (AS) and syn‐syn (SS) rotamers are determined from the variation of the OH proton chemical shift and of the rotamer composition with the pyridine concentration. The bridge methyl group has no effect upon the association constant of a syn OH group. Association constants are the same for the syn OH groups in the AS and syn‐anti (SA) rotamers of the diols, being slightly higher than for the alcohols. In contrast, values for a single syn OH group in the SS rotamers of the diols are significantly lower. Hydrogen bond acidity A values, determined for some congested alcohols and diols by the NMR method of Abraham, confirm that the syn OH protons of SS rotamers are less acidic than the single syn OH proton of an AS or SA rotamer. A values, with the notable exceptions of those for propan‐1,3‐diol and butan‐1,4‐diol, correlate with pyridine hetero‐association constants. Copyright © 2008 John Wiley & Sons, Ltd.

Influence of Chemical and Structural Properties of Functionalized Polythiophene‐Based Layers on Electrochemical Sensing of Atrazine

“…These imprinted cavities, keeping the memory of the targets at the molecular level, explain the selectivity which can be expected from these sensing structures. [19] To compare the ability of PEDOT, NICP, and washed MICP to detect the presence of newly added pesticide targets, thanks to establishment of new interactions between the probe-functionalized monomer units and the target molecules, [30,31] the modified gold electrodes were immersed for 10 min in ACN solutions containing both LiClO 4 0.1 mol L À1 and pesticide at various concentrations ranging from 10…”

“…In other words, whatever the thickness, MICP copolymers are the sensing layers which show the most accurate sensing properties towards atrazine target molecules. On the contrary, although the ethylenedioxy residues of the EDOT monomers can also interact with the triazine ring based ATZ molecules through hydrogen bonds, [30] PEDOT homopolymers are the worst sensing layers, since the corresponding Q r values remain very low. These observations can be explained in terms of structural and chemical properties of MICP, NICP, and PEDOT.…”

Enthalpy of cooperative hydrogen bonding in complexes of tertiary amines with aliphatic alcohols: Calorimetric study

“…Studies of hydrogen bond formation in aliphatic alcohols have been carried out with different experimental methods, for example, vapor pressure [3,4] and calorimetric measurements [5][6][7][8], infrared (FTIR) spectroscopy [9][10][11][12][13][14] and nuclear magnetic resonance (NMR) [15][16][17][18][19] techniques. The authors attempted to solve two major tasks in these studies.…”

1H NMR study of the hetero‐association of non‐symmetrical diols with pyridine; GIAO/DFT calculations on diols

“…In the following, association constants are numbered in accordance with previous publications 46, 50, 51. For a monohydric alcohol, the association constant, K 3 , is given by Eqn :52 where [M] o is the analytical alcohol concentration, [py] o that of pyridine, δ M and δ Mpy the chemical shifts of the OH proton in free and in pyridine‐complexed alcohol, respectively, and B = [M] o + [py] o + 1/ K 3 .…”