Neutron crystallographic and molecular dynamics studies of the structure of ammonia-cellulose I: rearrangement of hydrogen bonding during the treatment of cellulose with ammonia

Abstract

The hydrogen bond arrangement in a complex of cellulose with ammonia has been studied using neutron crystallography in combination with molecular dynamics simulations. The O6 atom of the hydroxymethyl group is donor in a highly occupied hydrogen bond to an ammonia molecule. This rotating ammonia molecule is donor in partially occupied and transient hydrogen bonds to the O2, O3 and O6 atoms of the hydroxyl groups of other chains. The hydrogen atom bound to the O3 atom is disordered but it is almost always involved in some type of hydrogen bonding. It is donated in a hydrogen bond most of the time to the O5 atom on the same chain. However, it also rotates away from this O5 atom to be donated to an ammonia molecule part of the time. On the other hand the hydrogen atom bound to the O2 atom is free from hydrogen bonding most of the time. It is donated in a hydrogen bond to the O6 atom on a neighboring chain only with a relatively small probability. These results provide new insights into how hydrogen bonds are Electronic supplementary material The online version of this article (

Water in Crystalline Fibers of Dihydrate β-Chitin Results in Unexpected Absence of Intramolecular Hydrogen Bonding

“…Another implication is that it might be expected that in the binary complexes of cellulose or chitin with other mobile solvent molecules, that the O3 hydroxyl group will hydrogen bond with the solvent molecules rather than O5. In fact in the complex of ammonia with cellulose the hydrogen atom on O3 is found to be disordered, being donated in a hydrogen bond most of the time to O5 on the same chain, but rotating away to also be donating to the ammonia molecule part of the time [11] .…”

“…Understanding the structural and chemical properties of these feedstock materials can be of fundamental importance to the development of more efficient or new processing conditions. Thus recent determination of the complete structures of the various crystal forms of cellulose using high resolution fiber diffraction [1] – [11] has helped guide new approaches to the efficient conversion of cellulosic biomass into biofuels. [12] , [13] In these studies X-rays were used to visualize the arrangement of carbon and oxygen atoms that make up the molecular skeleton of the cellulose chains, and neutrons were used to visualize the smaller and more mobile hydrogen atoms involved in hydrogen bonding.…”

Chirality and bound water in the hierarchical cellulose structure

“…All-atom MD simulations have been used to study the properties of cellulose in a broad context. This includes studies on the crystal structure of cellulose microfibrils (Matthews et al 2006;Wada et al 2011;Oehme et al 2015bOehme et al , 2018, and, as mentioned before, various aspects of the microfibril twist (Yui et al 2006;Matthews et al 2006;Yui and Hayashi 2007;Paavilainen et al 2011;Hadden et al 2013;Bu et al 2015;Conley et al 2016;Kannam et al 2017). Other studies have looked at the interactions of microfibrils with water (Yui et al 2006;Bergenstråhle et al 2008;Maurer et al 2013;Kulasinski et al 2015Kulasinski et al , 2017Lindh et al 2016;O'Neill et al 2017), their response to elevated temperatures (Matthews et al 2011(Matthews et al , 2012bZhang et al 2011); their mechanical properties (Paavilainen et al 2012;Saitoh et al 2013;Molnár et al 2018), aggregation and disintegration (Oehme et al 2015a;Paajanen et al 2016;Silveira et al 2016), chemical modification (Wada et al 2011;Paajanen et al 2016), enzymatic degradation (Beckham et al 2011;Orłowski et al 2015), and dissolution in ionic liquids (Gross et al 2011;Uto et al 2018); the pyrolytic degradation of cellulose (Zheng et al 2016;Paajanen and Vaari 2017); and radiation-induced defects…”

Neutron Technologies for Bioenergy Research

“…19,20 Neutron fiber diffraction on samples of cellulose isolated from biomass has helped to reveal that, under controlled anhydrous conditions, ammonia can penetrate into the cellulose fibers to form crystalline complexes. 21 Upon removal of ammonia, the cellulose is found in another crystal form called cellulose III I , which has greater susceptibility to enzymatic hydrolysis. 22 These results on model systems have been used to alter AFEX pretreatment to improve overall hydrolysis yield in preliminary studies with corn-stover biomass.…”