subsecret
Hazard to Others
Posts: 424
Registered: 8-6-2013
Location: NW SC, USA
Member Is Offline
Mood: Human Sadness - Julian Casablancas & the Voidz
|
|
High Purity Isopropanol
Earlier today, I was extracting capsaicin from spicy peppers. The extraction was running, so I began work on the second part of the procedure:
1) I boiled the (diced) peppers in water under reflux.
2) I then planned to add a copious amount of NaCl for the next step.
3) I added about 50ml of 91% isopropanol to dissolve the capsaicin-based oil.
When I designed this procedure, I expected the NaCl to push the isopropanol out of the water. At the same time, the capsaicin-based oil would
(hopefully) dissolve in the isopropanol. The NaCl added earlier would separate the water and the isopropanol, and the water could be discarded. I
tested this procedure on my clean 91% isopropanol, and sure enough, two separate phases could be seen. When I tried this on the capsaicin-containing
mixture, however, no phase change could be seen, even after waiting several minutes.
Despite my failure to extract the capsaicin, I deduced that this "salting out" could be used to purify OTC isopropanol. Here is the procedure I
designed:
1) A large amount of NaCl to the OTC 70% isopropanol.
2) After two phases are observed in the solution, the lower (aqueous) phase is drained and discarded.
3) The upper phase is transferred into a distillation apparatus, and heat is applied. In theory, this would further purify the isopropanol.
I developed several questions during this procedure:
What are some ways to improve the yield of the capsaicin extraction?
Would adding the NaCl salt out enough water to bring the concentration of isopropanol above the azeotropic 91%? If so, how large would the increase
be?
Any help is appreciated. Thank you.
|
|
|
Nicodem
|
Thread Moved
29-6-2013 at 00:08 |
subsecret
Hazard to Others
Posts: 424
Registered: 8-6-2013
Location: NW SC, USA
Member Is Offline
Mood: Human Sadness - Julian Casablancas & the Voidz
|
|
Where was it moved?
|
|
|
Finnnicus
Hazard to Others
Posts: 342
Registered: 22-3-2013
Member Is Offline
|
|
Beginnings, owing to the lack of references/citations.
|
|
|
Stearic
Harmless
Posts: 5
Registered: 5-7-2013
Member Is Offline
Mood: No Mood
|
|
The link below provides a process using Non-Iodized NaCl. First you would salt the Isopropyl Alcohol with Non-Iodized NaCl in a seperatory funnel to
provide moderately dry Isopropyl Alcohol. And then dry it even further using anhydrous Magnesium Sulfate. (Anhydrous MgSO4 can be produced from baking
Epsom salt in an oven at 483 F.)
http://books.google.com/books?id=J55D3HcgPuoC&pg=PA67&am...
[Edited on 11-7-2013 by Stearic]
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
<img src="../scipics/_warn.png" /> Take care when distilling propan-2-ol, as explosive <a href="viewthread.php?tid=21495">peroxides may be
present</a>. <img src="../scipics/_warn.png" />
|
|
|
Sublimatus
Hazard to Others
Posts: 108
Registered: 8-6-2011
Member Is Offline
Mood: No Mood
|
|
Vogel's has a procedure for obtaining clean, dry propan-2-ol.
As bfesser points out, propan-2-ol forms peroxides, which can become concentrated during distillation and explode, which is also addressed in Vogel's.
From Vogel's Textbook of Practical Organic Chemistry, 5th Edition, 1989, Section 4.1, Page 402: | Quote: | 11. PROPAN-2-OL
Two technical grades of propan-2-ol (isopropyl alcohol) are usually marketed having purities of 91 per cent and 99 per cent respectively. The former
has a b.p. of about 80.3 °C and is a constant boiling point mixture with water. Propan-2-ol may contain peroxide, which if present must be removed
before dehydration is attemped. Therefore test for peroxide by adding 0.5 ml of propan-2-ol to 1 ml of 10 per cent potassium iodide solution
acidified with 0.5 ml of dilute (1:5) hydrochloric acid and mixed with a few drops of starch solution just prior to the test: if a blue (or
blue-black) coloration appears in one minute, the test is positive. To remove peroxide heat under reflux 1 litre of propan-2-ol with 10-15 g
of solid tin(II) chloride for half an hour. Test a portion of the cooled solution for peroxide: if iodine is liberated, add further 5 g portions of
tin(II chloride and heat under reflux for half-hour periods until the test is negative. Add about 200 g of calcium oxide and heat under reflux for 4
hours, and then distil, discarding the first portion of distillate. The water content may be further reduced by allowing the distillate to stand over
calcium metal or a Type 5A molecular sieve for several days, followed by further fractionation. Anhydrous propan-2-ol has a b.p. 82-83 °C/760 mmHg.
It should be noted that peroxide generally redevelops during several days. |
You can download a PDF of the reference from the Sciencemadness Library. There's a lot of good stuff in there (Brauer, etc.), I'd recommend giving it
a browse.
[Edited on 7/11/2013 by Sublimatus]
|
|
|
bfesser
Resident Wikipedian
Posts: 2114
Registered: 29-1-2008
Member Is Offline
Mood: No Mood
|
|
The Preperative-Organic Bible:
<a href="http://library.sciencemadness.org/library/books/vogel_practical_ochem_3.pdf" target="_blank">A Text-Book of Practical Organic Chemistry
Including Qualitative Organic Analysis by Arthur I. Vogel</a> <img src="../scipics/_pdf.png" />
Commonly (lovingly) referred to as 'Vogel's Organic', 'Vogel's Bible', or simply 'Vogel'.
Read it, revere it, <em>worship it!</em>
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
