Computational insight into networking H‐bonds in open and cyclic forms of glucose

Abstract

We have studied the intramolecular H‐bonds existing in cyclic and open forms of glucose using B3LYP/6‐311++G(d,p) level, AIM, and NBO methods. The theoretical results indicated that based on acidity values, (ΔHacid), glucose in the open form is more acidic than cyclic form. The acidity values for open and cyclic glucose (332 and 338 kcal/mol) exhibit significantly lower values (i.e., stronger acid) than the reported acidity values for α‐/ß‐anomers of D‐glucopyranose and simple alcohols. Because their conjugate bases are more stabilized through trifurcated and bifurcated intramolecular H‐bonds. AIM analysis showed normal H‐bonds in the conjugate bases of open glucose (O‐Glc), bifurcated, and normal H‐bonds in the conjugate base of cyclic glucose. In the conjugate base of glucose, the O–H···O bonds are categorized as mostly electrostatic and strong, whereas multiple interactions including C–H···O, C–H···H–C (dihydrogen bonding), C–H···C–H, and C=O···H are categorized as weak H‐bonds. The NBO results confirm that the O–H···O intramolecular H‐bonds should be the strongest among all H‐bonds existing within glucose.