[brycebb]

Hey guys, I had a problem in my organic chem class that is driving me nuts.  The problem is a substitution, in which it can be either SN1 or SN2, we have to decide, and there are of course two reactants.  The reactants are  n-Propyl Methanesulfonate and 3-aminopentane.  Now what I originally did was have the lone pair on the nitrogen act as a nucleophile and attack the mesylate and release a a propyl group that has a negative charge on an oxygen.  I then had the nitrogen attached to the mesylate group act as a Leaving group and then had the nucleophilic oxygen/propyl group attack the secondary carbocation.  So essentially I made a SN1 reaction.  Now I know this is wrong but I am not sure what else I could do.  I did think of having the 3-aminopentane attack the primary carbon in in the propyl group that is attached to the oxygen on the n-Propyl Methansulfonate, but I do not see this happening because of too much steric hinderance.  Anyone have any advice or can give me some input on this reaction?  I would greatly appreciate it.

[discodermolide]

I think you have it reversed.
The mesylate on the oxygen is a good leaving group. Have another go at it.

[orgopete]

The first issue is to understand the difference between SN1 and SN2 reactions. An SN1 reaction is essentially formation of a carbocation first. Tertiary best, then secondary, and not primary (unless allyl or benzyl). An SN2 reaction is attack first and has a transition state. Is this an SN1 or SN2 reaction?

Generally, the leaving group in either reaction is a weaker base than the nucleophile. If you wished to compare the basicity of an amine, alcohol, and methanesulfonate, you need to look at their acids. A ammonium salt (~11), alcohol (~16), and a methanesulfonic acid (~-3?). Which do you think will form?