Obtaining 3D Structures and Why They are Needed

The 3D structure of a raolectile can be derived either from experiment or by computational methods. Regardless of the origin of the 3D model of the molecule under consideration, the user should alway.s be aware of how the data were obtain- 

2 Repre enlalion of Chemical Compounds 95 Table 2-6. Coinmon file forinats for representing chemical structures. 

In principle, two different classes of structure generators can be distinguished, namely empirical approaches,. such as fragment-based or rule- and data-based 

This section describes briefly some of the basic concepts and methods of automatic 3D model builders. However, interested readers are referred to Chapter II, Section 7.1 in the Handbook, where a more detailed description of the approaches to automatic 3D structure generation and the developed program systems is given. 

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