Unprecedented Detection of Distinct Barriers Involving Formally Enantiotopic Substituents: Phenyl Rotation in Solid Diphenyl Sulfoxide

Casarini, Daniele; Lunazzi, Lodovico; Mazzanti, Andrea

doi:10.1002/1521-3773(20010702)40:13<2536::aid-anie2536>3.0.co;2-r

Cited by 23 publications

(12 citation statements)

References 23 publications

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“…Selected geometrical parameters of the sulfoxides 2-8 calculated at B3LYP/6-311G(d,p) level, are listed in Table 3. Geometrical parameters derived from X-ray crystal structures of these sulfoxides 35,36 are also included in Table 3, where available. Sulfoxides are strongly pyramidalized.…”

Section: Conformational Spaces For the Pyramidal Inversion Of Simple mentioning

confidence: 99%

Pyramidal inversion mechanism of simple chiral and achiral sulfoxides: A theoretical study

2007

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The pyramidal inversion mechanism of simple sulfoxides was studied, employing ab initio and DFT methods. The convergence of the geometrical and energetic parameters of H2SO and DMSO with respect to the Hamiltonian and basis set was analyzed in order to determine a computational level suitable for methyl phenyl sulfoxide (3), methyl 4-cyanophenyl sulfoxide (4), diphenyl sulfoxide (5), 4,4'-dicyanodiphenyl sulfoxide (6), benzyl methyl sulfoxide (7) and benzyl phenyl sulfoxide (8). The DFT B3LYP/6-311G(d,p) level was chosen for further calculations of larger sulfoxides. The barriers DeltaE calculated for the pyramidal inversion mechanism of sulfoxides 3-8 are in the range of 38.7-47.1 kcal/mol. These values are in good agreement with the experimental barriers for racemization via the pyramidal inversion mechanism. A resonance effect of a phenyl ring selectively stabilizes the transition state conformations, decreasing the energy barrier for pyramidal inversion by about 3 kcal/mol, compared to a similar molecule without a phenyl substituent. Introducing electron withdrawing groups (cyano) at the para positions of the phenyl ring(s) causes a further decrease of the energy barrier.

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Section: Conformational Spaces For the Pyramidal Inversion Of Simple mentioning

confidence: 99%

Pyramidal inversion mechanism of simple chiral and achiral sulfoxides: A theoretical study

2007

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“…24 In another example of phenyl flipping in crystals reported by Casarini and coworkers, rates of rotation of 3.5 × 10 2 and 1.2 × 10 3 s -1 were calculated at ambient temperature for the two formally enantiotopic phenyl groups of diphenyl sulfoxide. 25 If a single point of attachment reduces the rates of rotation of phenyl groups in crystals, one may expect that the linkage of a benzene ring along its 1,4-axis may restrict its rotational dynamics even further. However, coalescence analysis by 13 C CPMAS NMR in the case of 3 revealed rates of rotation of ca.…”

Section: Thermal Stability Of the Benzene Clathrate: Dsc And Tg Analysismentioning

confidence: 99%

Molecular “Compasses” and “Gyroscopes.” III. Dynamics of a Phenylene Rotor and Clathrated Benzene in a Slipping-Gear Crystal Lattice

et al. 2002

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Samples of 1,4-bis(3,3,3-triphenylpropynyl)benzene 3 were prepared by Pd(0)-catalyzed coupling of 3,3,3-triphenylpropyne (1) and 1,4-diiodobenzene. The structure of compound 3 is such that the central phenylene can play the role of a gyroscope wheel, while the alkyne bond and trityl groups can act as an axle and shielding frameworks, respectively. Crystals grown from benzene and dichloromethane were characterized by X-ray diffraction, variable-temperature (13)C CPMAS NMR, quadrupolar echo solid-state (2)H NMR, and thermal analyses. The rotational dynamics of benzene molecules and phenylene groups were characterized in terms of 6-fold rotation and 2-fold flipping models, respectively. The possibility of a gearing mechanism between adjacent benzene molecules and phenylene groups suggested by the clathrate structure was investigated. However, it was found that 6-fold rotation of benzene molecules at 300 K occurs in the gigahertz regime (or higher) and 2-fold flipping of phenylene groups in the kilohertz range in a structure that can be described as a slipping-gear lattice. The rotational dynamics of the phenylene group in the solvent-free structure were remarkably similar to those in the clathrate, and both are among the fastest known for phenylene rotation in solids. The results presented here provide a valuable starting point for the design and analysis of crystalline solids with correlated molecular motions.

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“…The same group studied the dynamic process of trimethyl (3‐phenylpropyl) ammonium bromide ( 2 ) in the solid‐state and measured methyl rotation (~30 kJ mol −1 ), trimethylammonium rotation (43.4 kJ mol −1 ) and phenyl rotation (~55 kJ mol −1 ) . Lunazzi et al have measured distinct barriers to the phenyl rotation in solid diphenyl sulfoxide ( 3 ) finding in average a value of 56.5 kJ mol −1 . Houk, Garcia‐Garibay et al studied a series in dendrimeric molecular rotors and their deuterated derivatives .…”

Section: Introductionmentioning

confidence: 99%

Libration of phenyl groups detected by VT‐SSNMR: Comparison with X‐ray crystallography

Nieto¹,

Cabildo²,

García³

et al. 2018

Magnetic Reson in Chemistry

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The X-ray crystal structure of 2-benzyl-1H-benzimidazole, 2BnBzIm, was determined at 293 K showing no dynamic phenomena (disorder) of any class. On the other hand, some C NMR signals were absent in the CPMAS spectrum (100 MHz, 300 K). We decided to carry out variable-temperature SSNMR and discovered that the missing signals are ortho and meta carbons of the phenyl ring of the benzyl group. Line-shape analysis and the Eyring equation were used to determine the barrier, which was compared with the calculated DFT for the gas phase that it is much lower.

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Unprecedented Detection of Distinct Barriers Involving Formally Enantiotopic Substituents: Phenyl Rotation in Solid Diphenyl Sulfoxide

Cited by 23 publications

References 23 publications

Pyramidal inversion mechanism of simple chiral and achiral sulfoxides: A theoretical study

Pyramidal inversion mechanism of simple chiral and achiral sulfoxides: A theoretical study

Molecular “Compasses” and “Gyroscopes.” III. Dynamics of a Phenylene Rotor and Clathrated Benzene in a Slipping-Gear Crystal Lattice

Libration of phenyl groups detected by VT‐SSNMR: Comparison with X‐ray crystallography

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