Aggregate Formation by Dipole Forces

Relations have already been stated on page 92 for expressing in the case of parallel and anti-parallel arrangement, the potential of the mutually attracting particles as a function of the distance these relations indicate directly the conditions under which the two dipoles assume the parallel position, and so are able to promote chain formation, and those under which they prefer to assume the anti-parallel arrangement. 

The ratio (parallel arrangement) to rl (anti-parallel) determines this. It depends upon whether the centers of the molecules are brought nearer together by one arrangement or the other. Conditions for HF are illustrated in Fig. 23, due to G. Briegleb in this case 2rl (44 43) so 

If a dipole—C=0, OH, NH2—is heavily loaded with purely homopolar groups, it may happen that the minimum distance within which the polar 

The properties of the molecules involved then resemble very closely those of the corresponding hydrocarbon. An excellent example of this is shown in Table 43 which gives boiling points, according to Briegleb, of the isomeric butyl alcohols as a measure of inter-molecular forces. 

Under the influence of a sufficiently strong dipole, even the electron shells of a symmetrical molecule, such as a tetrahedral one can be deformed so much that a considerable dipole moment results. There is likewise a possibility, under certain conditions, of a deformation of the nuclear framework. For example, Ulich was able to demonstrate a very considerable dipole moment (2.46 X 10 ) in liquid SnCh, while in the gaseous state the substance has a moment of practically zero and exhibits complete tetrahedral symmetry. The same is true with AICI3, TiCh and other metallic halides. Moreover, highly symmetrical molecules may deform one another, as we may infer, for example, from the lattice of the monoclinic modifications of CBr4 described by Mark.  

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