[ostudent]

Hi all,

I understand the basics of part a. And in part b, I understand that sodium hydride allows for an irreversible reaction. But I am curious to know why sodium hydride is added for step 1 in part b. Why isn't the same mechanism used as in part a (add TsCl in pyridine)

Also attached: my proposed mechanism for part b.

[rolnor]

There is no apparent reason for this, its just to show that NaH can be used in this way.
Normally you would use pyridine as base when making tosylate.
I think it should be commented that CH3SH is a gas with very unpleasant smell, you would try to avoid using it.