Tutorial Morgan Algorithm

In this simplified example of phenylalanine, in the first iteration the methyl groups arc given a value of I in the first classification step because they contain a primaiy C-atom, The methylene group obtains a value of 2, and the methine carbon atom a value of 3. In the second step, the carbon atom of the methyl group on the left-hand side obtains an extended connectivity (EC) value of 2 because its neighboring atom had a value of 2 in the first classification step. 

The c arlrnn atoms of the other two methyl groups (on the right-hand side) obtain an EC value of 3 because they arc adjacent to the racthinc carbon atom. The carbon atom of the methylene group obtains an EC value of 4 in the second rcla.xation process, as the sum (1 + 3) of the eonncctivity values of its neighboring atoms in the first iteration. 

The extended connectivity (EC) value of an atom of the first sphere (i) results from the number (n) of neighboring atoms (NA) according to Eq, (7)  

When all the EC values of the atoms have been calculated, the number of equivalent classes (e) for the first sphere is determined. The number of classes is equivalent to the number of different EC values. 

(n the second and higher sphere(s) the EC value for each atom is calculated by summing the EC values of the directly connected neighboring atoms of the former sphere (Eq, (8)  

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Figure 2-42. The Morgan Algorithm generates an unambiguous and unique numbering of phenylalanine (see Tutorial, Section 2,S,J,1).

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