Building up of Structure Skeleton

Building up the structure skeleton is effected by means of the GRAPH command GRA, i.e. it determines whether the structure skeleton consists of chains and/or rings and the length of chains or size of rings (Fig. 104). In addition, it determines the bonds between atoms. The basic commands are  

If you wish to build up rings with more than 8 atoms it is necessary to define a chain first and then a bond (Fig. 104). As long as there are no details for atoms and bonds, all atoms are regarded as carbon atoms with undefined bonds. 

The position of the rings is always horizontal in this mode (Fig. 105). 

The direction of rings (up or down) can be indicated by a modification of the command (Fig. 106)  

You can also use the command GRAPH to determine side chains on rings. Therefore it is essential to know the numerical order of the relevant atoms. If you have first created a ring and subsequently a chain, counting starts clockwise at the ring. DISPLAY shows the present structure with its numbering of the single atoms (Fig. 107). 

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