[Violagirl]

This Tuesday for my O Chem lab, we have to synthesize banana oil. I have couple of concerns about it and wanted to know if somebody might be able to give me any tips on how I can properly do a few of the techniques without worrying about doing something wrong. We have to submit an NMR and IR sample towards the end. My TA has not shown us how to set an NMR sample yet but for IR, I had a hard time with it when I had to do it for a demo last week as my TA was really fast about explaining it. I know you have to rinse the salt plates first with a solution, we used methylene chloride and used disposable pipets. I had a hard time using the pipet in keeping the liquid within it and when I tried putting the drops onto the plates, it kept wanting to come out and I wasn't sure what to do to keep it in the pipet. I know after, you have to wipe it with a Kim wipe and then you can put your sample on it and then submit it for the IR analysis but wanted to know what to do to keep both the cleaning solution and my sample in the pipet without it running on me. My other concern, what's the best way to take down a simple distillation apparatus? I know after you run the experiment, it's good to remove the round bottomed flasks to clean out the products when finishing the experiment but afterwards, what's the best way/what's best to take down first to avoid anything breaking? I've been having a hard time figuring that out too.  Any suggestions/tips/advice is really appreciated!!

[voidSetup]

For the IR, you should be using a glass pipette for the methylene chloride.  Keep the methylene chloride next to the plates and whatever waste container the rinse is going into so that it doesn't need to be transferred far.  Do not tilt the pipette sideways or else the DCM will squirt out.  Also, after you've sucked up the solvent in the pipette, keep the pipette bulb squeezed a little bit and you can keep it from falling out.

For the sample, I would usually just dip the pipette (no pipette bulb) into the oil and let a little bit of the sample come into the tip by capillary action.  You can then place it on the salt plate by pushing down on the top of the pipette with your thumb to push the sample out of the tip.

[Violagirl]

Thanks for your input! My TA is just having us use disposable pipets where we have to place a rubber bulb on the top and then having us throw them away when we are done. I think he might have said to let air in before sucking in the methylene chloride and sample too but am not sure. Does that sound right at all?   

Also, what's the best, safest way to take down a simple distillation apparatus? Seems silly but my TA has been getting on me for the way I've taken it down. 

[discodermolide]

Thanks for your input! My TA is just having us use disposable pipets where we have to place a rubber bulb on the top and then having us throw them away when we are done. I think he might have said to let air in before sucking in the methylene chloride and sample too but am not sure. Does that sound right at all?   

Also, what's the best, safest way to take down a simple distillation apparatus? Seems silly but my TA has been getting on me for the way I've taken it down. 

Take off the receiving flask(s), remove the condenser after disconnecting it from the water supply, take off the still head, remove the flask from the heating apparatus and wash everything.

[fledarmus]

Thanks for your input! My TA is just having us use disposable pipets where we have to place a rubber bulb on the top and then having us throw them away when we are done.

Methylene chloride is a very low viscosity solvent and has a tendency to run all over everything. It is also low boiling, and tends to partially evaporate when you apply a vacuum with the rubber bulb, then run all over from the increased pressure from your hands warming the bulb. Not the easiest solvent in the world to handle with a pipette.

As voidSetup suggested, don't bother with the rubber bulb for your IR sample. Dip the tip of the pipette into your solution, then put your fingertip over the upper end of the pipette to cap it. Move the pipette tip to your IR plate and release your finger to allow a drop to fall on the plate. A little practice over the top of your solution will allow you to figure out how deep you need to dip the pipette to let just the right amount drop back out.

[Violagirl]

Thank you all for the *delete me*!