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You know how when you carry out a reaction with many compounds, when drawing the reactions you just draw a line at a right angle to the bond with a 'R' at the end (see image)?


Then you can specify what group R is in a table (eg: $\ce{OMe}$). However, if instead of adding a substituent to a benzene ring, you have pyridine? How can you specify it?

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The issue, I think, is to specify how the pyridine is connected. This means you have to identify which carbon on the pyridine ring is connected. This picture shows the numbering:

pyridyl carbon numbering

So, using your example the structure and names of the various possibilities would be (using connections on the 3-position of the benzonitrile ring as an example):

example structures

I'm sure you can generalise from this example.

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There is another configuration where the nitrogen is connected to the first compound and a hydrogen is added to the para position in the pyridine ring. – LDC3 Apr 19 '14 at 16:04

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