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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: shak22 on December 03, 2012, 03:06:54 AM

Title: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:06:54 AM

hello,
i have no bubbles in distillation of phenylacetone under vacuum, the heat is about 100c, and the vacuum pump produce around 20 torr.

is that normal? please help me.

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: discodermolide on December 03, 2012, 03:11:13 AM

You mean 1-phenylpropan-2-one? If so it has a BPt. of 214-216°C at normal pressure.
So in your case I would get a better vacuum. Check everything for leaks, 100°C seems a bit high for the bath temp.
But in your case go for a better vacuum first.

Title: Re: no bubbles in distillation of hello, phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:15:54 AM

i have a vacuum pump with a vacuum gauge that state that my vacuum is at 20 torr, the temp that phenylacetone should evaporate under such vacuum is around 110-120c.
any other segestion?

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:20:04 AM

in addition,
i have done this at a higher temp and the matirial just went throw the condencer.. as a liquid..

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: discodermolide on December 03, 2012, 03:22:23 AM

To be sure you did put 1-phenylpropan-2-one into the distillation apparatus?

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:23:05 AM

yes

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:23:41 AM

it's basiclly a mixter..
somthing should be boiled...

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: discodermolide on December 03, 2012, 03:32:21 AM

I take it the mixter = mixture?
I would dismantle the distillation apparatus and start again. Make sure all the joints are gas tight.

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:36:28 AM

yes a mixture.
it's the third time i'm trying this...
any segestion?

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:38:41 AM

and i put silicone grease all over the joints..

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: discodermolide on December 03, 2012, 03:39:44 AM

I take it that suggestion = suggestion.
What else is in the mixture?
My suggestion again: I would dismantle the distillation apparatus and start again. Make sure all the joints are gas tight.

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: shak22 on December 03, 2012, 03:45:28 AM

some toleune and water - very little because i have disttiled them at normal disttilation

i realy can't figure this out.. i shold create some bubbles right?
thank you by the way!

Title: Re: no bubbles in distillation of phenylacetone under vacuum
Post by: discodermolide on December 03, 2012, 04:55:02 AM

As I said, re-build the distillation apparatus and get a better vacuum.