I'm still having a little bit of issues with this. So last week I did a test run to try and get the Grignard initiated. I used some 1-bromoundecane that was sitting around in the lab, and I dried it on molecular sieves for a day or two just to see if it might help. I also have some new Mg turnings that are very shiny so they look good. I added a drop of the 1-bromoundecane and 50uL of ethyl iodide. I heated the solution up to reflux, it got cloudy and the Mg turned black. I added another drop of the alkyl halide and let it reflux for a little bit. After a few minutes the Mg very quickly turned shiny again, so I figured the reaction had started. I took the solution off of the heat, and with every drop of the alkyl halide the bubbles would come off of the Mg. After all the alkyl halide was added i refluxed for another 15 minutes or so and all of the Mg was consumed. So this one worked very well, I reacted it with cyclohexanone and the IR looked good.
A couple of days later I decided to try it again with my TBDMS-protected 9-bromononanol. I let the sample sit on the vacuum pump (I think its pulling about 1mmHg vacuum) for about 3 hours or so to try and eliminate any residual moisture. I went to do the Grignard and the Mg turned black again when I got it to reflux. I let it reflux for like 30 minutes and the Mg did not turn shiny again. I would add another drop here and there but it still wouldn't go. Eventually after all of the alkyl halide was added the Mg was still black and some white precipitates had formed in the solution. I let it reflux for like an hour and nothing, so I just gave that attempt up at that point.
Is it possible there is still some water in my sample that is preventing it from initiating? Is the blackness on the magnesium a MgO coating? Also is it reasonable to dry my sample on molecular sieves or CaCl2, or is the vacuum pump the best way to go when your sample is from a previous step and not something that was bought commercially?