Study of the temperature‐dependent conformational averaging of ¹H NMR resonances in vinylcyclopropane through the use of ab initio methodology and Boltzmann statistics

Use of 13C chemical shift surfaces in the study of carbohydrate conformation. Application to cyclomaltooligosaccharides (cyclodextrins) in the solid state and in solution

“…As we have stated above and discussed in more detail in our previous report, 16 this is hampered by the fact that most of the NMR data available for carbohydrates is from studies carried out in solution, and as a result the measurements are affected by conformational averaging. [5][6][7] Although we have shown that these effects can be taken into account through the use of high-quality ab initio potential energy diagrams and Boltzmann statistics, 35 the methodology is only accurate for small molecules with few degrees of conformational freedom. Therefore, 13 C NMR data for single oligosaccharide conformers, such as those obtained from CP/MAS studies on crystalline samples, are required for our purposes.…”

Molecular Dynamics and NMR Parameter Calculations

“…Two methods that do not involve liquid simulations, but can be used to predict chemical shifts of liquids are the quantum cluster equilibrium (QCE) method [2,43] and the Boltzmann averaging method [44]. We discuss them briefly here, and present some results obtained using these methods in Section 11.3…”

“…The expectation value for the NMR property is obtained for the canonical ensemble by directly substituting these functions and carrying out a numerical integration. Swalina et al [44] discuss the Boltzmann averaging method, and use it in a study of the temperature dependence of chemical shifts of an isolated molecule. They compare the results with a MD study.…”

“…The Boltzmann method applied in a discrete way (summing over clusters rather than generating a function and integrating) is equivalent to the QCE method. The Boltzmann averaging method can also be readily extended to study solvent effects [44].…”

Research involving NMR spectroscopy at undergraduate institutions in the United States

“…A similar ab initio methodology has been devised to predict chemical shift variations as a function of temperature. The applicability of the method was demonstrated with vinylcyclopropane [33].…”