Physical Properties and Theoretical Chemistry

The annulation of 4//-thiopyran and cyclohexane rings in 50a results in the planarity of the heterocycle and a half-chair conformation of the carbocycle (81KGS1342). On the other hand, a boat conformation of the 2//-thiopyran ring was found in the crystal of224b [91JCS(P2)2061], Other geometrical parameters were within the limits of the expected values (Fig. 2). 

Crystal and molecular structures of 2,4,4,6-tetraphenyl-4//-thiopyran-1-oxide (143) and the corresponding 1,1-dioxide 141a were investigated to show the boat conformations of the heterocycles as well as an interesting 

MO calculations were performed rarely for thiopyrans except for an MNDO study of 2 [84ZN(A)267], Charge distribution and orbital interaction concepts were explored in an interpretation of model reactions of thiopyrylium ions with azides giving 68 and the corresponding 3,5-unsub-stituted thiopyrans (84T3549) as well as for the equilibria between 1 and 2 or 167 and 168, respectively (92JOC4431). 

Interpretation of H and 13C NMR spectra has been a part of almost all synthetic work on heteropyrans. Complete assignments using 2D NMR or other more advanced techniques still seem to be exceptional [92JCS(P2)1301]. Typical values of H and 13C NMR characteristics for some 2H- and 4//-heteropyrans are given in Tables V, VI, VII, and VIII. 

Ultraviolet spectra of heteropyrans have been used mainly for characterization purposes. No theoretical calculations of the spectral patterns have yet been done. Typical UV absorption characteristics of some thiopyrans and teluropyrans are collected in Table IX. Analogous insight into the UV absorption of selenopyrans is still lacking. 

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A. Physical Properties and Theoretical Chemistry 1. Theoretical Chemistry... 

R. Brown, Physical properties of nitrogen, in Mellor s Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. 8, Suppl. 1, Nitrogen, Part 1, pp. 27-149, Longmans, London, 1964. 

The important role of radicals and radical ions in various branches of chemistry (e.g., electrochemistry, radiation chemistry, macromolecular chemistry), their remarkable physical properties and reactivity, as well as the specific problems in a quantum chemical approach, make this region interesting from the theoretical point of view. 

Polymer and Coatings (MST-7), Structure/Properties Relations (IVlST-8), and Theoretical Chemistry and Molecular Physics (T-12), Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, NM 87545... 

Bayard, F., Decoret, C. and Royer, J. (1990). Structural aspects of polymorphism and phase transition in organic molecular crystals. In Structure and properties of molecular crystals—studies in physical and theoretical chemistry, Vol. 69, pp. 211-34. Elsevier, Amsterdam. [188]... 

In this chapter an explanation is presented of certain engineering aspects that are important in understanding the mechanical properties of wood. Individual factors such as growth, environment, chemicals, and use can greatly affect the physical and mechanical properties of the wood material. A theoretical model is presented to explain the relationship between physical properties and chemistry of wood at three distinct levels macroscopic or cellular, microscopic or cell wall, and molecular or polymeric. These three levels and their implications on material properties must be understood to relate both wood chemistry and wood engineering from a materials science standpoint. When this is accomplished, the treatment and processing of wood and wood products can be controlled to yield more desirable and uniform properties. 

J. R. Flick and S. E. B. Petrie, Studies in Physical and Theoretical Chemistry, 10, 145-163 (1978). (Volume title Structure and Properties of Amorphous Polymers. Edited by A. G. Walton. Contains the Proceedings of the Second Symposium on Macromolecules, held in Cleveland, Ohio, October 31-November 2, 1978). 

Bunker P R and Howard B J 1983 Symmetries and Properties of Non-Rigid Molecules a Comprehensive Survey (Studies in Physical and Theoretical Chemistry 23) ed J Maruani and J Serre (Amsterdam Elsevier) p 29... 

The physical properties and chemistry of NO determine its biological fate and potential sites for interaction. NO is a highly diffusible compound because of its low molecular weight and reasonable hydrophobicity and solubility, NO is theoretically able to reach anywhere within cells and tissues (Feldman et al., 1993). Practical limits exist on the diffusion potential of NO, however, due to its many possible chemical interactions. The greatest factor limiting the availability of NO may be its rapid interaction with... 

Theoretical organic chemistry is principally concerned with the structure of molecules and - in reactions - of transition states. In contrast physical chemistry and theoretical chemistry are also tackling the bulk properties and, more importantly, are bridging the gap that separates them from the molecular properties. Physical organic chemistry, invented by Hammett [16], occupies an intermediate position and has in time become the... 

Krtswski, R.J. Labovitz, H. Sieglaff, C.L., pp.67-76 in "Structure and Properties of Amorphous Polymers", A.G. Walton (Ed.), Studies in Physical and Theoretical Chemistry, Volume 10, Elsevier Scientific Publishing Company, Amsterdam, 1980. Flick, J.R. Petrie, S.E.B., pp.145-171, ibid. 

W. F. van Gunsteren, in Modelling of Molecular Structures and Properties, Studies in Physical and Theoretical Chemistry, Vol. 71, J.-L. Rivail, Ed., Elsevier, Amsterdam, 1990, pp. 463-478. On Testing Theoretical Models by Comparison of Calculated with Experimental Data. 

Quack M (1983) Detailed symmetry selection rules for chemical reactions. In Maruani 1, Serre 1 (eds) Symmetries and properties of non-rigid molecules a comprehensive survey, vol 23 Studies in physical and theoretical chemistry, vol 23. Elsevier Publishing Co., Amsterdam, pp 355-378... 

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