oneselections
Harmless
Posts: 6
Registered: 14-9-2022
Location: Europe
Member Is Offline
Mood: Sustainable
|
|
Isopropyl Alcohol Boilingpoint
Hi,
I'm new to chemistry and this forum, and wanted to start out with a question.
I am experimenting a little at home, and I want to do a distillation by evaporating IPA from my boiling flask to my receiver flask as a test.
My question is, I have read that you can lower boiling point by using vacuum.
Ay what temperature under vacuum does IPA start to evaporate without boiling?
I have read that under 67mBar around 30-35c should be sufficient.
Best Regards
|
|
|
B(a)P
International Hazard
Posts: 1139
Registered: 29-9-2019
Member Is Offline
Mood: Festive
|
|
https://en.m.wikipedia.org/wiki/Isopropyl_alcohol_(data_page)
The vapour pressure tab on this site should answer your question.
|
|
|
teodor
National Hazard
Posts: 924
Registered: 28-6-2019
Location: Netherlands
Member Is Offline
|
|
oneselections, I would put several questions that you can ask yourself before doing the experiment. Maybe they will allow you to understand the
process better.
1. What is the purpose of the distillation?
2. Why do you need a vacuum?
3. How do you plan to cool the receiver to prevent product loss?
4. How do you plan to prevent possible peroxide concentration in the source flask?
5. Which portions of distillate do you plan to keep and which portions do you plan to discard?
|
|
|
DraconicAcid
International Hazard
Posts: 4356
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
IPA boils at such a low temperature, why do you want to muck around with vacuum distillation? That technique is far more applicable to things with
very high boiling points.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
Dr.Bob
International Hazard
Posts: 2751
Registered: 26-1-2011
Location: USA - NC
Member Is Offline
Mood: No Mood
|
|
"At what temperature under vacuum does IPA start to evaporate without boiling?"
Most solvents can evaporate well below their BP at atmospheric pressure, but slowly, look at water evaporate from a puddle, or acetone from a drip on
a fume hood. The question might be at what temperature does it evaporate quickly enough to be useful for a distillation, and for IPA (and many
organic solvents), that would be about 100- 200 mbar for a temperature that is fairly low. That is why aspirators used to be used for rotovaps for
many years, as they can pull a vacuum at or below that range.
But vacuum distillations provide very little purification of the liquid, unless it is quite high boiling, as most solvents have a high vapor pressure
at 100-200 mbar, so they all distill to some degree then, thus a mixture distills. For purification of the solvent, high BPs at sTP are better, for
quick evaporation of solvent to get the solute back, a rotovap is great. Same for just removing mostly pure solvent to recover it.
|
|
|
Lionel Spanner
Hazard to Others
Posts: 168
Registered: 14-12-2021
Location: near Barnsley, UK
Member Is Offline
|
|
Quote: Originally posted by DraconicAcid  | | IPA boils at such a low temperature, why do you want to muck around with vacuum distillation? That technique is far more applicable to things with
very high boiling points. |
Or things that decompose below their boiling points.
|
|
|
Rainwater
National Hazard
Posts: 937
Registered: 22-12-2021
Member Is Offline
Mood: Break'n glass & kick'n a's
|
|
ipa can be used in a soxhlet extractor to collect anthocyanin from purple cabbage. Lowering the pressure allows the apparatus to run at very low
temperatures, preserving the target compound, which is air sensitive.
The distillation took place at room temperature, but special measures were needed to cool the condencer(ice)
"You can't do that" - challenge accepted
|
|
|
oneselections
Harmless
Posts: 6
Registered: 14-9-2022
Location: Europe
Member Is Offline
Mood: Sustainable
|
|
Thank you,
|
|
|
oneselections
Harmless
Posts: 6
Registered: 14-9-2022
Location: Europe
Member Is Offline
Mood: Sustainable
|
|
| Quote: Originally posted by teodor | oneselections, I would put several questions that you can ask yourself before doing the experiment. Maybe they will allow you to understand the
process better.
1. What is the purpose of the distillation?
A: Just to test how it workspractically
2. Why do you need a vacuum?
A: To try out my vacuumpump and try something new
3. How do you plan to cool the receiver to prevent product loss?
With an ice bath
4. How do you plan to prevent possible peroxide concentration in the source flask?
Don't know what this is 
5. Which portions of distillate do you plan to keep and which portions do you plan to discard? |
Neither, this is just for fun.
|
|
|
teodor
National Hazard
Posts: 924
Registered: 28-6-2019
Location: Netherlands
Member Is Offline
|
|
oneselection,
Please read this thread: http://www.sciencemadness.org/talk/viewthread.php?tid=21495 .
The vacuum distillation is very useful but not easy technique which requires much patience before you will get satisfactory results. The good
practical way to start is to distill liquids which otherwise require too high temperature. I mean that you can synthesise some interesting things and
then purify them by vacuum distillation.
Another interesting experiment is to poor ethanol or acetone in a flask, put the thermometer and look how applying vacuum will decrease the
temperature. With some liquids you can go well below 0C. With addition of some solids you probably can get very low temperatures and this could be a
topic for investigation.
Another application of your vacuumpump could be drying different solids in a vacuum dessicator.
|
|
|
oneselections
Harmless
Posts: 6
Registered: 14-9-2022
Location: Europe
Member Is Offline
Mood: Sustainable
|
|
| Quote: Originally posted by teodor | oneselection,
Please read this thread: http://www.sciencemadness.org/talk/viewthread.php?tid=21495 .
The vacuum distillation is very useful but not easy technique which requires much patience before you will get satisfactory results. The good
practical way to start is to distill liquids which otherwise require too high temperature. I mean that you can synthesise some interesting things and
then purify them by vacuum distillation.
Another interesting experiment is to poor ethanol or acetone in a flask, put the thermometer and look how applying vacuum will decrease the
temperature. With some liquids you can go well below 0C. With addition of some solids you probably can get very low temperatures and this could be a
topic for investigation.
Another application of your vacuumpump could be drying different solids in a vacuum dessicator. |
Thank you for this reply and your input, I will look into this option
|
|
|
Texium
|
Thread Moved
26-9-2022 at 12:03 |
Texium
Administrator
Posts: 4619
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
See my blog post about vacuum distillation: https://texiumchem.com/2020/06/03/vacuum-distillation-of-ani...
Look up the ∆Hvap (heat of vaporization) value for isopropanol, and you can calculate its boiling point at any pressure, or the pressure
needed to reach a desired boiling point, using the Clausius-Clapeyron Equation. Make sure to put temperatures in Kelvin.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
