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Hi all,

I am reading up a bit on alkylation.  What  I am looking at right now is electrophilic alkylation of chitosan
using iodomethane.

In this articlehttp://cat.inist.fr/?aModele=afficheN&cpsidt=15271730, they use sodium hydroxide to deprotonate, with the finding that excess sodium hydroxide leads to increased yields of the quarternary amine, but also leads to selectivity of O alkylation.  My question is...why is this?  Surely O alkylation would be preferable regardless, because O is a more stable anion than N and should deprotonate first allowing attack.  However, an electrophilic methyl cation can attack the N lone pair before deprotonation of hydroxyl group.

Then, why would excess hydroxide lead to quartnernization?

I found this page but I wasn't able to get the full article as I'm on vacation and don't have access to my work's journal subscriptions.