Hydrogen bond cooperativity in polyols: A DFT and AIM study

Cooperativity in alkane‐1,2‐ and 1,3‐polyols: NMR, QTAIM, and IQA study of O─H…OH and C─H…OH bonding interactions

“…Two series of polyols are considered. The first features a well defined, slightly curved, hydrogen‐bonded OH … OH chain in a series of alkane‐1,3‐polyols previously studied by Parra and Streu 19 (Figure 1). A hydrogen‐bonded conformer of propane‐1,3‐diol (tG'Gg'), 1 , is extended so as to construct polyols 1 – 7 (Figure 1).…”

“…The series of 1,3‐polyols is an ideal test bed for exploring intramolecular cooperativity, and several characteristics can be used to determine its importance, notably 1 H NMR shifts, interatomic distances, and atom–atom interaction energies. This is by no means an exhaustive list of the possibilities for exploring hydrogen bonding, and other theoretical values, based on QTAIM analysis, have been exploited elsewhere 19, 82–84 …”

“…The tG'Gg' repeat unit was chosen arbitrarily, and obviously the results and conclusions would be the same for tGG'g, its mirror image. Rather than view the effects of extending the chain in both directions around a central propane‐1,3‐diol motif, 19 we preferred to extend it in the tail direction only, from propane‐1,3‐diol, 1 , to pentadecane‐1,3,5,7,9,11,13,15‐octol, 7 (see Scheme 1). There are two ways of looking at the propagation of cooperative effects, either up the chain from tail to head or down the chain from head to tail.…”

“…In the context of hydrogen bonding, this implies that bond strengths should be mutually enhanced, that is, that the strengths of two interacting bonds should be higher than those of the isolated bonds 6 . Cooperativity in long chains or clusters of small monomers or mixtures of different monomers has been widely studied by theoretical methods, 3,7–18 but work on intramolecular cooperativity going beyond two or three interacting bonds is much more limited 19–23 . It is generally assumed that in carbohydrates, where there are chains or clusters of OH groups, many features, for example, stability, molecular recognition, and binding with acceptors, are determined by long‐range cooperative effects 24–27 .…”

Cooperativity effects of intramolecular OH…O interactions on pK a values of polyolalkyl sulfonic acids in the gas phase and solution: a density functional theory study

“…Such an interaction increases the stability of the molecular conformation in which it occurs. For instance, Parra and Streu carried out density functional theory (DFT) calculations to investigate cooperativity in two basic model systems: 1,3‐propanediol and 1,8‐napthalenediol . Moreover, high level ab initio calculations were carried out on diacetamide–X (DA—X) dimers, X = HCN, CH 3 OH to study the energetics and cooperative phenomena in intermolecular three‐center hydrogen‐bond (H‐bond) interactions pertinent to two‐center H‐bond interactions .…”