Mass and length dimensions

X-ray diffraction and spectroscopy have provided the modem chemist with an amazing wealth of stmctural information on organic molecules. Molecules long ago ceased to be just lists of symbols and numbers on a sheet of paper, at best with a few dots and dashes here and there, and nowadays spring into the third dimension with their stereochemical characterization. Modern chemistry is stereochemistry. As a consequence, encouraged by the beautiful models built from balls and sticks or drawn in full color by computers, we now handle molecules as we do ordinary objects of the macroscopic world. We look at them, we weigh them, and in many other ways we size them up. 

This book is mainly concerned with the phenomena that occur when molecules aggregate. Molecular packing is defined here as the process by which an ensemble of 

Once the nuclear coordinates are expressed in the inertial reference frame, one can locate the extreme points occupied by a nucleus in the molecule along each of the three inertial axes, thus defining three limiting molecular dimensions (Table 1.1 and Fig. 1.1). The radii of the peripheral atoms (see below) may be added to these dimensions. The axis corresponding to the highest moment is perpendicular to the plane of maximum spread of nuclear positions - like, for example, the molecular 

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