[Grasshopper]

I'm trying to react hydroquinone with a haloalkane under basic conditions via a standard Sn2 reaction. I get quite a lot of dark brown gunk in the mixture- presumably due to oxidation of hydroquinone? I'm using oven dried glassware and anhydrous solvent (solvent degassed by bubbling N2 through it). Has anyone seen this before and are there any other good tips for preventing it? Thanks!

[wildfyr]

What base and solvent are you using?

[Grasshopper]

The solvent is anhydrous acetonitrile, and the base is potassium carbonate. I've also tried acetone which seemed to produce about the same result...
Thanks very much!

[wildfyr]

So I agree youre getting oxidation, and the reason is that hydroquinone, when deprotonated, is converted to benzoquinone. Benzoquinone is known for undergoing all sorts of oligomerization events. I know this is a strange suggestion, but perhaps try doing this with O2 present. Some of these side reactions are radical in nature and will be quenched by oxygen. I do not think a little water will hurt your reaction much if you leave it open to air.

I suggest checking scifinder before trying again on this one, I'm sure people have tried to double-Williamson ether hydroquonine before.

[Babcock_Hall]

I saw one or two promising-looking threads just by searching on "hydroquinone" here.  I am not certain that they would help, however.

[Grasshopper]

Interesting idea! I'll try less stringent inert atmosphere and see if it improves things at all...

[phth]

How to improve your results:  put the base in the oven at 160 ºC+ for a few hours, the hotter the shorter amount of time.  The base will dry out, and it will dissolve faster due to higher surface area; moarter and pestle.    Doing so will produce a faster reaction rate minimizing the time to form side products, and side products of side products..

[Grasshopper]

Thanks wildfyr and phth. I tried both of your suggestions. I think it did improve things a bit (the reaction ran a bit longer before the brown stuff appeared) but there was still brown stuff in the reaction mixture before the reaction ran to completion. Maybe it isn't possible to get rid of it completely. At least the tlc shows that the brown gunk sits on the baseline so should be OK to remove by column.

Thanks again!