Another, more important question- Depending on where you look, ie rhodium versus wikipedia versus where ever, the structure of MDA is different. Sometimes the amine portion is on the very end of the chain while other times there is a methyl on the end and the amine part is between that and the rest of the chain. Is it that it makes no difference, or is one wrong? It seems to me that moving a group's position would affect it somehow. Maybe the fact that it's the position on the chain and not the ring that changes it doesn't matter as much? If that's the case then why the big difference between ketone and aldehyde? This is very confusing to me.
MDA/safrylamine is what is known as a secondary amine, thus there is an alkyl (in this case methyl) group attached to the alpha carbon:
You won't understand this matter until you study more, that much is clear The end results from the effort applied