High‐Resolution Rotational Spectroscopy Study of the Smallest Sugar Dimer: Interplay of Hydrogen Bonds in the Glycolaldehyde Dimer

Abstract

Molecular recognition of carbohydrates plays an important role in nature. The aggregation of the smallest sugar, glycolaldehyde, was studied in a conformer-selective manner using high-resolution rotational spectroscopy. Two different dimer structures were observed. The most stable conformer reveals C2 -symmetry by forming two intermolecular hydrogen bonds, giving up the strong intramolecular hydrogen bonds of the monomers and thus showing high hydrogen bond selectivity. By analyzing the spectra of the (13) C and (18) O isotopologues of the dimer in natural abundance, we could precisely determine the heavy backbone structure of the dimer. Comparison to the monomer structure and the complex with water provides insight into intermolecular interactions. Despite hydrogen bonding being the dominant interaction, precise predictions from quantum-chemical calculations highly rely on the consideration of dispersion.

Water Triggers Hydrogen‐Bond‐Network Reshaping in the Glycoaldehyde Dimer

“…The resulting molecular clusters can then be probed with different spectroscopic techniques to reveal their structural preferences and shed light on the preferred anchoring sites for both intra‐ and intermolecular interactions . Among the simple sugars, glycoaldehyde (Gly), HOCH 2 −CHO, has been the object of numerous experimental and theoretical studies . From a structural standpoint, Gly is often considered to be the simplest sugar (diose), as it is the smallest molecule containing both an aldehyde and a hydroxyl group (aldoses).…”

Water Triggers Hydrogen‐Bond‐Network Reshaping in the Glycoaldehyde Dimer

“…The experimental structures are compared to the previously observed (Gly) 2 . [11] As shown in Figure 2 a, (Gly) 2 exhibits C 2 spatial symmetry with two equivalent intramolecular HBs between the hydroxy and the carbonyl groups. Upon the addition of one water molecule, a remarkable rearrangement occurs.…”

“…The structural preferences of the dimer [9] and its complex with water [10] were also studied using IR and IR-VUV spectroscopies, respectively. More recently, Zinn et al [11] studied the self-aggregation of Gly using rotational spectroscopy and provided accurate structural information of two qualitatively different Gly dimers in the gas phase.…”

“…[4] Among the simple sugars, glycoaldehyde (Gly), HOCH 2 ÀCHO, has been the object of numerous experimental and theoretical studies. [5][6][7][8][9][10][11] From a structural standpoint, Gly is often considered to be the simplest sugar (diose), as it is the smallest molecule containing both an aldehyde and a hydroxyl group (aldoses). Gly has been shown to be a key intermediate in the formation of larger sugars through the formose reaction, [5] and it has even been discovered in the interstellar medium.…”

Water-Induced Structural Changes in Crown Ethers from Broadband Rotational Spectroscopy

“…MW spectroscopy in supersonic jets offers one of the most powerful experimental methods to precisely determine the structure of an isolated molecule or cluster, and it provides access to molecules without chromophore groups. [16][17][18] Because of this, potential influences of the chromophores on the formation of water clusters, as studied in previous, UV-based spectroscopic studies (vide supra) 9-13 can be investigated. For MW spectroscopy, the molecules need to be polar and have to be brought into the gas phase.…”