[discodermolide]

Well you did not do everything as the literature said, you still had water left when you added PBr₃ and the reaction mixture after the HBr addition was not dry!

That's a shitty NMR, sorry, you need to get rid of the solvent signal at around 5ppm. Get the integration sorted out and make the peaks bigger so you can actually see them properly.

[Messi]

That's a shitty NMR, sorry, you need to get rid of the solvent signal at around 5ppm. Get the integration sorted out and make the peaks bigger so you can actually see them properly.

I agree. That signal around 5ppm was water.

Well you did not do everything as the literature said, you still had water left when you added PBr₃ and the reaction mixture after the HBr addition was not dry!

So what should I see after I rotavap my solution of HBr with my amino-alcohol? Should I see no liquid, or very little liquid? Should I see my solid/salt?

The reason I am so confused is because prolinol has a boiling point of 74-76 °C at 2 mmHg while water has a boiling point of 100°C.

[discodermolide]

I don't know what you will see but I guess it may be an oily semi-solid mass.
You won't be able to remove all the water which is why they add ethanol. You need to do that, you can even do it several times. Then you add the PBr₃.
Why are you confused about the boiling points?  Your compound will not vanish in the rotavap. the BPt. of water at 2mmHg is not 100°C but around 0°C. So a standard water aspirator will do the job for you.

[Goala]

Im only a 3rd yr student here. But it's odd that you are using a rotaryevaporator to evaporate water. For all the reactions I have done, I simply add a drying agent like magnesium sulphate. From what my lab instructors have told me, rotaryevaporating water takes a very very long time. I find it peculiar that the experimental procedure yoou are following states to do so.

[discodermolide]

Im only a 3rd yr student here. But it's odd that you are using a rotaryevaporator to evaporate water. For all the reactions I have done, I simply add a drying agent like magnesium sulphate. From what my lab instructors have told me, rotaryevaporating water takes a very very long time. I find it peculiar that the experimental procedure yoou are following states to do so.

Are you going to remove 130mL or more water with a drying agent? You will need kg of the stuff. I see absolutely no problem by rotavaping it off.

[Goala]

Are you going to remove 130mL or more water with a drying agent? You will need kg of the stuff. I see absolutely no problem by rotavaping it off.

Well, how long do you think it will take to rotaryevaporate it? I imagine it could take a good 35-45 minutes to rotaryevaporate 50-75 mL of water under 760 torr pressure. Am I correct in making this assumption?

[discodermolide]

You use a reasonable vacuum then it will go faster. But why does it need to be done rapidly, so what, if it takes 45 minutes you set up your next reaction.
Drying agents are only used to remove the last traces of water from a solvent  not to remove large quantities.

[Messi]

Thanks disc!

I posted a picture of my "product" down below. It has been under the rotovap for two hours. I don't see crystals/solid like I thought I would... So, can I continue my reaction and add PBr₃? Or should I let it on the rotovap overnight? I am unsure! I also posted a video below!



View My Video

I was tilting my RBF with my contents in it in this video.

[discodermolide]

Has it been treated with the hot ethanol yet?
If not, then do this let's say twice.

[Messi]

Has it been treated with the hot ethanol yet?
If not, then do this let's say twice.

Yes, it has been treated with hot ethanol twice!

[discodermolide]

OK. It looks like you have quite a bit of it. Take a pasteur pipette and try and get rid of than oily liquid. Don't throw it away.
Take a small part of your yellow gum? and do the next step. How much have you got 5 g or so? Try the next step on 0.5g and see what happens.

[Messi]

OK. It looks like you have quite a bit of it. Take a pasteur pipette and try and get rid of than oily liquid. Don't throw it away.
Take a small part of your yellow gum? and do the next step. How much have you got 5 g or so? Try the next step on 0.5g and see what happens.

I think my oily liquid is my yellow gum? I tried transfering a small portion of my oily liquid to a small rbf... a real hassle. Should I react my PBr₃ with this oily liquid as a "test rxn"?

Shown below is my black oil.

[discodermolide]

Where is the other part? The yellow solid.
I meant use the yellow solid for the test reaction.
Have you run NMR's yet?

[Messi]

Where is the other part? The yellow solid.
I meant use the yellow solid for the test reaction.
Have you run NMR's yet?

Unfortunately the other picture gave the illusion of there being a yellow solid. There is no yellow solid. It is just the color of the walls of the RBF after the oil dripped down the side of the walls. All there is in my RBF is a black oil that moves very slowly.

No, I haven't ran an NMR yet. I was following the procedure that I had showed you earlier. Technially after I add HBr, I should have a my salt in solid form... but I just have this gooey oil.

[discodermolide]

OK, that's clear now.
Try a test reaction on that dark red oil.
Have you run an NMR, what is the yield, assuming that's your product?