Intramolecular dynamics resonance

The effects of intramolecular dynamics (vibration and rotation) on nuclear shielding have been observed as temperature dependence of resonance... 

Intramolecular dynamic processes that are fast on the NMR timescale are also observable in the H-NMR spectrum of the bound Hoechst molecule. Resonance averaging is observed for the H2/H6 and H3/H5 protons of the phenol group, which is consistent with the environments on either side of the ring being averaged by rapid ring-flipping motions about the C4-C2 axis. This occurs despite the appar-... 

Tricarhonylbis(N, N-dimethyldithiocarbamato)tungsten, (W(CO)3(dmtc)2), has been synthesized, and two distinct intramolecular dynamic processes have been identified by variable temperature NMR studies of this seven-coordinate molecule. The sodium salt of dimethyldithiocarbamate reacts with tetracarbonyldiiodotungsten to form the above product, W(CO)s(dmtc)2. Analytical, IR and NMR data confirm this formulation. The NMR spectrum at —llO C has three distinct resonances, two of which initially coalesce independently of the third (aG+ = 8.1 heal moT ) as the temperature is increased. All three carbon monoxide signals are averaged at higher temperatures (aG+ = 9.0 heal moT ). Reversible loss of one CO occurs upon heating to form an insoluble blue W(CO)2(dmtc)2 compound. 

The behavior of molecules within the intermolecular bottleneck, that is to say intramolecular dynamics, is also of interest. For example, trajeaories can be trapped for signficant periods of time within resonance zones inside the intermolecular bottleneck. A classical resonance is a region of phase space where, locally, the condition... 

Although exchange reactions, where bonds are broken and formed, are fundamentally different from a chemical point of view to the intramolecular dynamic phenomena that we have discussed so far, in principle they are the same in terms of observation by NMR spectroscopy. Consider a very simple chemical process, the exchange of protons between HCl and HBr. NMR spectroscopy shows exchange between two sites with resonant frequencies Va and Vb and mean lifetimes Ta and Tb- The lifetimes are equal if the two... 

Jameson C J 1981 Effects of intermolecular interactions and intramolecular dynamics on nuclear resonance. Bull Magn Res 3 3-28... 

Callegari A, Rebstein J, Muenter J S, Jost R and Rizzo T R 1999 The spectroscopy and intramolecular vibrational energy redistribution dynamics of HOCI in the u(OH) = 6 region, probed by infrared-visible double resonance overtone excitation J. Chem. Phys. 111 123-33... 

The resonance splitting of intramolecular modes in the crystalline state is often called Davydov splitting or factor group splitting . In contrast to the static field effects of the crystal, this splitting is due to the dynamical interaction of the constituents in the primitive cell... 

Binsch, G., The Study of Intramolecular Rate Processes by Dynamic Nuclear Magnetic Resonance, 3, 97. 

Engel, Y. M., and Levine, R. D. (1989), Vibration-Vibration Resonance Conditions in Intramolecular Classical Dynamics of Triatomic and Larger Molecules, Chem. Phys. Lett. 164, 270. 

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