Comparative quantum-chemical study of complexes of cyclic ether with ethylene glycol

A Symmetric Recognition Motif between Vicinal Diols: The Fourfold Grip in Ethylene Glycol Dimer

“…Thus,t he almost exclusive observation of as ymmetric dimer in the spectra points at ap ronounced case of chirality synchronization in the recognition process, opposite in sign to the case of trifluoroethanol. [35] 7.6 kJ mol À1 higher or 15 %l ess stable than the 4H structure,atriply hydrogen-bonded structure,s imilar to structures discussed before, [4][5][6]9] is located and denoted 3H (Figure 1). Again, all its hydrogen bonds are intermolecular, but one OH is dangling.…”

“…[2] Ethylene glycol or 1,2-ethanediol is ap articularly valuable model system for the study of multiple hydrogenbonded dimers and carbohydrate interactions, [3] because it allows for av ast range of quantum-chemical options to be explored. Indeed, the question of its preferred dimer structure has been addressed repeatedly by theory, [4][5][6] but not by experimental techniques.B ecause of the torsional flexibility of ethylene glycol, there are several possibilities how the four OH groups of the dimer can engage in hydrogen bonds.None of the previously proposed structures involves more than three hydrogen bonds among these OH groups. [4][5][6][7][8][9][10][11] We present unambiguous combined IR and Raman spectroscopic evidence that ethylene glycol in fact forms an S 4 -symmetric and thus non-polar and achiral dimer with four equivalent hydrogen bonds.U sing Gaussian 09, [12] an extensive search of the intermolecular potential-energy hypersurface at B3LYP-D3(BJ)/6-311 + G(2d,p) level (in short B3LYP) confirms that this structure wins over all triply hydrogen-bonded dimer structures by as ubstantial energy margin.…”

A Symmetric Recognition Motif between Vicinal Diols: The Fourfold Grip in Ethylene Glycol Dimer

“…Ethylene glycol or 1,2‐ethanediol is a particularly valuable model system for the study of multiple hydrogen‐bonded dimers and carbohydrate interactions, because it allows for a vast range of quantum‐chemical options to be explored. Indeed, the question of its preferred dimer structure has been addressed repeatedly by theory, but not by experimental techniques. Because of the torsional flexibility of ethylene glycol, there are several possibilities how the four OH groups of the dimer can engage in hydrogen bonds.…”

“…Because of the torsional flexibility of ethylene glycol, there are several possibilities how the four OH groups of the dimer can engage in hydrogen bonds. None of the previously proposed structures involves more than three hydrogen bonds among these OH groups …”

“…7.6 kJ mol −1 higher or 15 % less stable than the 4H structure, a triply hydrogen‐bonded structure, similar to structures discussed before, is located and denoted 3H (Figure ). Again, all its hydrogen bonds are intermolecular, but one OH is dangling.…”