Differentiating substitution from addition

Started by reising1
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reising1

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How is it possible to tell if a reaction is an addition or a substitution reaction? I tried to use "if an H or any other atom is removed from the electrophile, then it's substitution." But this doesn't seem to work.

For example, the reaction of cyclohexanone with pyrrolidine:

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I thought this was a nuclophilic substitution because a Hydrogen atom must have been removed from the ortho position on the cyclohexanone and from the nitrogen atom for the double bond to form. But nope, this is a nuclophilic addition then dehydration.