Benzo wacker failure or just low yield?

[notta234]

SWIM is very much a Newbee, and has just yesterday attempted his first benzo-wacker oxidation. SWIM has been slowly studying this topic for about 3 years now, but has only recentally started to actually persue it. He is an engineering student and has no chemistry background.
   Here is what SWIM would like to know: His first attempt at the MM wacker seemed to be filled with trouble from the beginning. SWIM decided to be a moron and prestir the benzo with the methanol. Once he realized what he did (15 min or so), he quickly measured and added the h20 and the PdCl2. In this hurry, Mr. Moron added too much water (he put the 50ml for a full reaction, when he is only doing a 1/2 reaction). He started to add the safrole/MeOH about an hour after all the previous stuff had stirred. This addition took about 1.25 hours, and didn't seem to heat up the flask at all. SWIM started to add external heat, and was suprised about how high he had to turn the temp up. Up until the temp was damn near 70c, there was only small amounts of precip running down the sides of the flask, and very little ever coming out of the condenser.  SWIM let it run like this for a few hours, until he decided that he might be doing more damage than good.  There was tons of burn precip on the sides of the flask, and the mixture itself had turned almost black.

SWIM wants me to find out if he should even try to do the separations or if he should just throw it all away. He is currently running his 2nd attempt, which seems to be going better.  This first black mixture has been stored in the freezer since it was done being butchered.

SWIM also had some questions about the reaction he is currently doing. This time he decided to do a 1/4 MM benzo so that he doesn't ruin more of his useful chemical. This time he prestirred the CORRECT chem with the methanol all night. He then added the benzo and the water and let stir for about 2 hours. The one nice little error SWIM made is that he put too much benzo in because of another moronic mistake. He beleives, though, that this is just a waste of chemical and not of concern for the reaction.

This time, SWIM wanted to be damn sure that atleast part of the reaction was working, so he added the safrole at a much quicker rate (all was added in about 3/4 hour). This time he did notice a very definite tempurature change which peaked at 44c before it started to go down (just a degree or two).  SWIM then added external heat (eventually to get to #4 on his hotplate) until the temp was about 55-58c. One thing he also noticed is that the safrole turned whatever product it touched to an almost red color, which had not happened previously. The reaction still seems to be terribly slow. This time, he is keeping the temp down to around 60c or below so that he doesn't burn the shit out of everything again. Some precip is dripping out of the condensor, but not anywhere near the 1 drop every 5 seconds that SWIM read somewhere on here. The reaction mixture is still somewhat dark blood red. Is it proper that the faster you stir the mixture, the more product seems to be coming over?

SWIM's done what he thought was a lot of reading, but he guesses it wasn't.  SWIM also understand that all the smart bee's out there don't really want to waste their time with questions that should probably not be asked, but he figures it won't hurt to try. SWIM does not expect any one person to respond to all of his problems, but it would sure be helpful if you all could help him out with some of the more major ones. He also has a couple more questions I'm going to add after this that he has in his mind right now.

1) He has a 200 or 300MM Graham condenser... would this be good to use as his condensor for the benzo wacker?
2) Do the 1/2 and 1/4 sized MM benzo's normally require more external heat to start/keep going?
3) Should SWIM have to keep the external heat on once the reaction has started, or is it supposed to be atleast partially self-sustatining?
4) Is there anything to be said about the speed of the stir-bar? SWIM has normally kept it just below the speed that it shoots shit everywhere... is this too fast?
5) Does it matter if SWIM doesn't have much precip coming down the condensor still? Should he keep upping the heat until it's closer to 1 drop every 5 seconds instead of 1 every 10 or 12 seconds?
6) SWIM has a three-necked flask. The third neck holds the thermometer. SWIM is curious how far down into the flask should this thermometer be placed?
7) SWIM lives in a very humid place. He noticed the large amount of condensation on the outside of the condensor. What are the chances of this happening inside the condensor and dripping down into the flask? And would this be a problem for this reaction?


SWIM feels that he's damn near learned more in the last two days of actually doing something than he did with the months of reading. He thanks you all in advance for any help you can provide. Also, please, this is his first time he's actually posted to web board, so if he's done anything wrong or asked a question that he should have been able to find the answer to, please let him know! He doesn't want to be one of those annoying newbee's that doesn't show the respect they should to everybody else who is willing to help!

Thanks

[OcoteaCymbarum]

1) He has a 200 or 300MM Graham condenser... would this be good to use as his condensor for the benzo wacker?
Yes, its perfect for your purpose

2) Do the 1/2 and 1/4 sized MM benzo's normally require more external heat to start/keep going?
I've never run a 1/4 but at normal scale it does heat up to around 60. Its not that important

3) Should SWIM have to keep the external heat on once the reaction has started, or is it supposed to be atleast partially self-sustatining?
You can do both, I havent seen any real difference between the 2

4) Is there anything to be said about the speed of the stir-bar? SWIM has normally kept it just below the speed that it shoots shit everywhere... is this too fast? no

5) Does it matter if SWIM doesn't have much precip coming down the condensor still? Should he keep upping the heat until it's closer to 1 drop every 5 seconds instead of 1 every 10 or 12 seconds? a drop every 5 seconds or 12 wont change anything

6) SWIM has a three-necked flask. The third neck holds the thermometer. SWIM is curious how far down into the flask should this thermometer be placed? look at your thermomether, there should be a line on it!

7) SWIM lives in a very humid place. He noticed the large amount of condensation on the outside of the condensor. What are the chances of this happening inside the condensor and dripping down into the flask? And would this be a problem for this reaction?
the condensation comes from the coldness of the water youre running trough the condenser, not because its humid outside!

AS far as the reaction...it does get darkblack/red, with a lot of black precipitate(hydroquinone), you really need to clean up the solution. You will see the oil falling out when you hydrolyse with chlorhydric acid. Are u sure you've read so much? 3 years?

[notta234]

7) SWIM lives in a very humid place. He noticed the large amount of condensation on the outside of the condensor. What are the chances of this happening inside the condensor and dripping down into the flask? And would this be a problem for this reaction?
the condensation comes from the coldness of the water youre running trough the condenser, not because its humid outside!

-- I'd imagine that the more humidity there is, the more water there is in the air to condense on the condensor. In dry enviroments, water evaporates more easily. I went out to Arizona and golfed 18 holes in 116 degree temps, and I wasn't drenched. If the water is condensing from the air on the outside of the condensor, isn't it possible to do the same inside? or is there not enough volume?

Are u sure you've read so much? 3 years?
-- When I say 3 years, I mean I started 3 years ago, took a little break... then spent the last 3 months or so raising money and doing research.  I've read damn near everything on rhodium on the subject, I've read Zubricks a few times... and spend time searching through posts. I did this both 3 years ago, and moreso recentally. The problem is that most of the things I'm not sure about aren't things typically convered in books (maybe because it's just obvious to everybody else).  Once I screw it up, I know where to look and what to look for.

Thanks for your reply, it makes me feel a hell of a lot better about the second reaction.  The first, I'd imagine, is still pretty damn fucked.

[Rhodium]

the condensation comes from the coldness of the water youre running trough the condenser, not because its humid outside!

That statement was so stupid that I don't even know how to begin disputing it. I will leave the question as from where the condensing water originates as an exercise to the reader.

If the water is condensing from the air on the outside of the condensor, isn't it possible to do the same inside?

Yes, definitely. If you are running a water-sensitive reaction in a humid laboratory environment it is imperative to attach a drying tube at the top of the condenser to prevent any water vapor from condensing inside the condensor and dripping into the reaction mixture.

[OcoteaCymbarum]

I think sometimes I imply things(at least in my head) and dont write them out. Or maybe its the langage barrier.

Of course the humidity comes from the air, what I tried to say(i only took a minute to write and didnt re-read myself) was that it condenses because of the cold water you run in. I've never seen under normal circumstances, water dripping off things for no reason, no matter how humid it is (ok except 100%). That what I tried to say by saying ot comes from the coldwater. The condensation would not occur if the columns wasnt cooled.

I guess ill be more careful, but for your knowing Rhodium, I've never flunked a single class, including university.