A deuterium NMR study of orientational order in tertiary-butyl bromide

Pettitt, Brian A.; Lewis, J. S.; Wasylishen, Roderick E.; Danchura, Werner; Tomchuk, E.; Bock, E.

doi:10.1016/0022-2364(81)90284-5

Cited by 11 publications

(13 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There are other sets of NMR activation energies that would be equally successful, but the tert -butyl group activation energy will be in the 17–23 kJ mol –1 range and the three methyl group activation energies will all be in the 7–12 kJ mol –1 range. The important point here is that all tert -butyl groups and their constituent methyl groups are contributing to the observed relaxation in various temperature regions between 85 and 303 K and the parameters that characterize these rotation are similar to the parameters found for similar planar organic van der Waals molecular solids. − ,− ,− There are significant systematic differences between the fitted and observed relaxation rates for the fit shown, especially at 53.0 MHz in the 160–220 K range in Figure . Other sets of four activation energies within the ranges given above will shift these differences between theory and experiment to other temperature ranges and to another NMR frequency, but they cannot be eliminated.…”

Section: Methods and Resultssupporting

confidence: 63%

“…Solid-state 1 H nuclear magnetic resonance (NMR) spin–lattice relaxation experiments are helpful in modeling the motion of tert -butyl groups [C(CH 3 ) 3 ] and their constituent methyl groups (CH 3 ). − In turn, the parameters that characterize these kinds of rotations contribute to the understanding of the angular anisotropies (for the rotations) in the intramolecular and intermolecular potentials in the solid state. , In these kinds of van der Waals molecular solids, composed of small covalently bonded organic molecules with tert -butyl groups, the molecules usually keep their isolated-molecule structure in the solid state, except perhaps for the orientations of the tert -butyl groups. Here we report and model the unusual dependence on thermal history of the temperature dependence of solid-state 1 H NMR relaxation measurements in 1,3,5-tri- tert -butylbenzene (TTB), a molecule of which is shown in Figure .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

Beckmann¹,

McGhie²,

Rheingold³

et al. 2017

J. Phys. Chem. A

View full text Add to dashboard Cite

Using solid-state 1H nuclear magnetic resonance (NMR) spin–lattice relaxation experiments, we have investigated the effects of several solid–solid phase transitions on tert-butyl and methyl group rotation in solid 1,3,5-tri-tert-butylbenzene. The goal is to relate the dynamics of the tert-butyl groups and their constituent methyl groups to properties of the solid determined using single-crystal X-ray diffraction and differential scanning calorimetry (DSC). On cooling, the DSC experiments see a first-order, solid–solid phase transition at either 268 or 155 K (but not both) depending on thermal history. The 155 K transition (on cooling) is identified by single-crystal X-ray diffraction to be one from a monoclinic phase (above 155 K), where the tert-butyl groups are disordered (that is, with a rotational 6-fold intermolecular potential dominating), to a triclinic phase (below 155 K), where the tert-butyl groups are ordered (that is, with a rotational 3-fold intermolecular potential dominating). This transition shows very different DSC scans when both a 4.7 mg polycrystalline sample and a 19 mg powder sample are used. The 1H spin–lattice relaxation experiments with a much larger 0.7 g sample are very complicated and, depending on thermal history, can show hysteresis effects over many hours and over very large temperature ranges. In the high-temperature monoclinic phase, the tert-butyl groups rotate with NMR activation energies (closely related to rotational barriers) in the 17–23 kJ mol–1 range, and the constituent methyl groups rotate with NMR activation energies in the 7–12 kJ mol–1 range. In the low-temperature triclinic phase, the rotations of the tert-butyl groups and their methyl groups in the aromatic plane are quenched (on the NMR time scale). The two out-of-plane methyl groups in the tert-butyl groups are rotating with activation energies in the 5–11 kJ mol–1 range.

show abstract

Section: Methods and Resultssupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

Beckmann¹,

McGhie²,

Rheingold³

et al. 2017

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…Since the T 1 of deuterium is in general anisotropic, we have used the above pulse sequences to measure the effective relaxation time characteristic of the system. [33][34][35][36] The temperature of the sample was controlled to AE1 K. Lineshape simulations of the spectra were performed by standard methods 37 using the MXQET computer program.…”

Section: Methodsmentioning

confidence: 99%

NMR studies of the molecular dynamics of tert-butyl chloride confined in the mesoporous molecular sieve MCM-41

Wasyluk

Peplińska

Klinowski

et al. 2002

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

The molecular dynamics of tert-butyl chloride (TBC) confined in the molecular sieve MCM-41 were investigated by measuring NMR linewidths, lineshapes, and 1 H and 2 H spin-lattice relaxation times. The temperatures of phase transitions of confined TBC are different from those in bulk. The behaviour of confined TBC can be explained assuming that the guest molecules form two kinds of molecular layers, one located at the pore surface and the other at the centre of the pore.

show abstract

“…tert- Butyl compounds have stimulated a large number of theoretical studies as well as have been the object of considerable experimental efforts to elucidate the nature of the disorder and, more specifically, the hindrance to the orientational disorder. − …”

Section: Introductionmentioning

confidence: 99%

“…As for the tert -butyl bromide dealt with in this paper, polymorphism has been the subject of an intensive work. ,,− ,,,,− , It exists in three solid phases, designated I, II, and III in order of decreasing temperature and is one of the compounds possessing two stable OD phases (I and II). OD phase I is stable between ca.…”

Section: Introductionmentioning

confidence: 99%

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

et al. 2006

View full text Add to dashboard Cite

Phase equilibria involving orientationally disordered (OD) and liquid phases of the two-component system between carbon tetrachloride (CCl4) and 2-methyl-2-bromomethane ((CH3)3CBr) have been determined by means of X-ray powder diffraction and thermal analysis techniques from 210 K up to the liquid state. The isomorphism relation between the OD stable face-centered cubic (FCC) phase of (CH3)3CBr and the metastable FCC phase of CCl4 has been demonstrated throughout the continuous evolution of the lattice parameters and the existence of the two-phase equilibrium [FCC + L] for the whole range of composition, despite the monotropy of the FCC phase for the CCl4 component with respect to its OD rhombohedral (R) stable phase. A continuous series of OD R mixed crystals is found, which confirms the R lattice symmetry of the OD phase II of (CH3)3CBr, for which the crystallographic results have been long-time misinterpreted. X-ray patterns of such a phase were indexed according to the recent single-crystal results obtained by Rudman (Rudman, R. J. Mol. Struct. 2001, 569, 157). In addition, some experimental evidences are given to confirm the number of molecules per unit cell (Z = 21). The thermodynamic assessment reproduces coherently the phase diagram for the stable [R + L] and [R + FCC] two-phase equilibria as well as for the partially metastable [FCC + L] two-phase equilibrium and provides a set of data for the thermodynamic properties of nonexperimentally available phase transitions of pure components. Surprisingly, the phase equilibrium involving R and FCC OD phases appears as one of the very few showing a solid-solid equilibrium with two extremes.

show abstract

A deuterium NMR study of orientational order in tertiary-butyl bromide

Cited by 11 publications

References 13 publications

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

NMR studies of the molecular dynamics of tert-butyl chloride confined in the mesoporous molecular sieve MCM-41

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Contact Info

Product

Resources

About

A deuterium NMR study of orientational order in tertiary-butyl bromide

Cited by 11 publications

References 13 publications

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State 1H Nuclear Spin Relaxation

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State 1H Nuclear Spin Relaxation

NMR studies of the molecular dynamics of tert-butyl chloride confined in the mesoporous molecular sieve MCM-41

Two-component System CCl4 + (CH3)3CBr: Extrema in Equilibria Involving Orientationally Disordered Phases

Contact Info

Product

Resources

About

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

Solid–Solid Phase Transitions and tert-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid-State ¹H Nuclear Spin Relaxation

Two-component System CCl₄ + (CH₃)₃CBr: Extrema in Equilibria Involving Orientationally Disordered Phases