Location: Cotton Structure and Quality Research
Title: Hydrogen Bonding in the Methanol Dimer Authors
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: February 19, 2010
Publication Date: April 28, 2010
Citation: French, A.D., Johnson, G.P. 2010. HYDROGEN BONDING IN THE METHANOL DIMER. Proceeding of the National Cotton Council Beltwide Cotton Conference, January 5-7, 2010, New Orleans, Louisiana. p. 1581-1584. Interpretive Summary: Hydrogen bonds are interactions between atoms that, despite individual weakness, are still thought to be extremely important to biology in general and cotton chemistry in particular. When viewing proposed structures, either from experiment or computer modeling, it is often difficult to decide whether a particular 3-dimensional arrangement corresponds to a hydrogen bond. The present work studied methanol molecules because their ability to form hydrogen bonds should be similar to that of cellulose, the main molecule in cotton fiber. The methanol molecules were placed in many different arrangements and quantum mechanics was used to calculate the energy and the wavefunction for each. The wavefunction, a description of the arrangement of the electrons in the molecules, was then analyzed for properties that would demonstrate the existence of a bond between the methanol molecules. Bonding was found for a wide range of arrangements of the two methanol molecules. This fundamental research is of interest to chemists and other scientists who are studying the biosynthesis, structure and chemical modification of cotton cellulose and other carbohydrate materials.
Technical Abstract: In this work, two methanol molecules are placed in different arrangements to study hydrogen bonding in carbohydrate materials such as cellulose. Energy was calculated as a function of both hydrogen bond length and angle over wide ranges, using quantum mechanics (QM). The QM wavefunctions are analyzed in terms of R. F. W. Bader's “atoms-in-molecules” theory. “Bond critical points” and “bond paths,” indicators of bond formation, were found over H...O distances from 1.5 to 3.5 Å, and O-H…O angles greater than 110°. Therefore, a wide range of geometries, especially those with long H…O distances, can correspond to hydrogen bonds. This range is wider than allowed by some geometric criteria.