Mesomorphic state of cyclotetradecane

Drotloff, Hansotto; Rotter, H.; Emeis, D.; Moeller, Martin

doi:10.1021/ja00259a031

Cited by 15 publications

(7 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The crystal undergoes a phase transition in the 173-153 K range, 53 the crystallographic details of which are not known. The solid-state 2 H NMR 25 and the 13 C NMR 24 spectra as a function of temperature indicate that the same conformation remains dominant in the melt, in a mesophase, and in the crystal at 150 K, with temperature-dependent conformational interconversion dynamics observed.…”

Section: Resultsmentioning

confidence: 92%

“…This is the conformation predicted to be lowest in energy in this (see Table 12) and previous studies. 55 Solid-state 2 H NMR 25 and the 13 C NMR 24 spectra have been obtained over a temperature range that includes the melt, a mesophase, and the crystal at 175 K. These studies conclude that the same conformation persists through these phase transitions with dynamics observed due to temperature-dependent conformational reorientation. This a For this set of spectra, j ) 77 with F(60,60) ) 1.5 required to determine the presence of one conformer over another with 95% confidence.…”

Section: Resultsmentioning

confidence: 94%

“…Vibrational spectroscopy is a useful technique in this area because it is able to report on the presence of each of the multiple conformations as distinct signals. [19][20][21][22] Solid-state NMR [23][24][25][26][27] has played an important role in these studies because of its ability to detect phase transitions, to distinguish between static and dynamic disorder, and to detect the presence of minor species.…”

Section: Introductionmentioning

confidence: 99%

“…The medium ring cycloalkanes have a long history as a testing ground for empirical treatments of conformational energetics and interconversions. − The cyclo C 7 −C 10 compounds have recently received extensive treatment by post-Hartree−Fock ab initio methods. , The major interest and challenge of these studies stem from the presence of multiple low-energy minima on the conformational energy surface. Vibrational spectroscopy is a useful technique in this area because it is able to report on the presence of each of the multiple conformations as distinct signals. − Solid-state NMR − has played an important role in these studies because of its ability to detect phase transitions, to distinguish between static and dynamic disorder, and to detect the presence of minor species.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Conformational Distinguishability of Medium Cycloalkanes in Crystals via Inelastic Neutron Scattering

2006

View full text Add to dashboard Cite

This paper begins an exploration of the use of the combination of DFT computations with experimental inelastic neutron scattering (INS) spectra as a method for establishing what conformation is present in a molecular crystal at low temperature. Presented here are INS spectra of a series of medium-sized cycloalkanes: C6H12, C7H14, C8H16, C10H20, C12H24, and C14H28. Optimized geometries and normal mode calculations were performed at B3LYP/6-311G(d,p) on the lowest energy conformations (i.e., those thermally accessible at the experimental temperature of 30 K). The calculated and observed spectra were analyzed for the best fit from each set of conformers, allowing a prediction of the dominant conformation in a conformationally rich system. For each cycloalkane, the calculated spectrum for the lowest energy conformer shows good agreement with experiment while the higher energy conformations have a much poorer fit. With little ambiguity, the lowest energy conformer is therefore predicted to be the dominant conformation, consistent with the diffraction data available for C6H12, C10H20, C12H24, and C14H28. These results indicate that INS spectroscopy may be a useful tool in determining the dominant conformation in a crystal lattice in cases such as this in which the intermolecular interactions are weak and the different conformers are calculated to have distinguishable spectra. Such an analysis is applied to the cases of C7H14 and C8H16 for which no low-temperature X-ray analysis is available. Clear structure predictions result, and the conformer observed is that computed to be of lowest energy for the molecule in isolation.

show abstract

Section: Resultsmentioning

confidence: 92%