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This is all about linearity of the molecule and steric hindrance. Consider the linear structure of ethylene glycol versus the branched structure of propylene glycol. EG can "stack" more easily and therefore engage in more intermolecular bonding than PG. More attraction means more energy required to vaporize. On the other hand, 1,3 propane diol, ...


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The original article on UFF is from 1992, so it is somewhat dated. The selection of "natural bond" values is explained on page 10028: a. Standard Bond Angles. The natural angles for the group 15, 17, and 18 main group elements are obtained from standard reference structures of the parent hydrides. Thus 0-3 has Bo = 104.5' from HzO, while S3 has Bo ...


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van der Waals forces is not another name for London dispersion forces. In his answer, airhuff has given IUPAC definition for van der Waals forces. London dispersion forces are the intermolecular forces that occur between atoms and between nonpolar molecules as a result of the motion of electrons in those atoms and molecules. They are induced dipole-induced ...


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There are too many definitions for something that seems to be incompletely understood and it is best to look at it operationally. There are forces of attraction between molecules. We know this because it is observed. Different types of molecules have different forces. I will only talk about the weakest of these, the "pure" van der Waals forces ...


1

The size of the cavity is one of the many factors collaborating to host-guest chemistry with cyclodextrin (CD). For example, depending on the size and the properties of the guest molecule, CD may form complexes with either the entire molecule or only a part of the molecule (The diameter and the volume of the cavity of β-CD are around $\pu{7.8 Å}$ ($\pu{0.78 ...


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