Physical and Theoretical Aspects

Physical and Theoretical Aspects.—Perhaps the most interesting development of the year has been concerned with the varying levels of sophistication which have been applied to theoretical work on halogenophosphines. For example, extended Hiickel calculations on cyanodifluorophosphine (1) have been found 2 to predict the observed non-linear P—C=N system. Using s- and p-orbitals only in the basis set, it was calculated that the cyanide group of (1) has a tilt of 9.4° (away from the fluorines), which compares favourably with the observed value of 8.8 0.8°.  

The same phosphine has been the subject of a semi-empirical SCF CNDO/2 study, and the results were compared with those obtained by ab initio 

Phosphorus trifluoride and pentafluoride have been studied by non- 

Fild and R. Schmutzler, in Organic Phosphorus Compounds , ed. G. M. Kosolapoff and L. Maier, Wiley-Interscience, New York, 1973, Vol. 4, p. 75. 

Photoelection spectra of a series of phosphines, including (3) and (4), have been reported, and used to assess lone-pair effects on torsional barriers. It is 

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Pyrrole is a colorless, slightly hygroscopic Hquid which, if fresh, emits an odor like that of chloroform. However, it darkens on exposure to air and eventually produces a dark brown resin. It can be preserved by excluding air from the storage container, preferably by displacement with ammonia to prevent acid-catalyzed polymerization. A review of the physical and theoretical aspects of pyrrole is found in Reference 4. Some physical properties of pyrrole are Hsted in Table 1. 

This area has been the subject of recent extensive reviews,590-592 which deal particularly with the physical and theoretical aspects. In this section, a more chemical and descriptive approach will be adopted. 

W.M. Siu and R.S. Cobbold, Basic properties of the electrolyte-Si02-Si system physical and theoretical aspects, IEEE Trans. Electron Devices, ED-26(11) (1979) 1805-1815. 

Before treating the structural and spectroscopic data pertaining to various pentadienyl entities, it is appropriate to examine some physical and theoretical aspects which should prove helpful to understanding and even predicting some of the features of metal-pen-... 

Physical and Theoretical Aspects.— Phosphorus pentafluoride continues to attract attention from those interested in theoretical aspects of structure, and from those more inclined to test the predictions of others. The most detailed ab initio calculations of the year lead to confirmation of Berry pseudorotation... 

Physical and Theoretical Aspects, IEEE Trans. Electron Devices, ED-26, 1805-1815. 

Before discussing the role of surfactants and their chemical structure in the preparation and stabUization of emulsions, it is important to have in mind a clear concept of the physical and theoretical aspects of liquid-liquid interfaces and the stabilization mechanisms available. Detailed discussions of these topics can be found in the works cited in the Bibliography. What follows is only a brief summary of some current thinking on the subject no attempt is made to provide a comprehensive overview. 

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