Author Topic: wash a solution  (Read 855 times)

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topdowner

  • Guest
wash a solution
« on: October 18, 2003, 06:25:00 PM »
Hi,

i must wash one solution with Sodium-chloride. But I don´t understand how. Can anybody please help me?

Rhodium

  • Guest
Washing solutions
« Reply #1 on: October 18, 2003, 06:41:00 PM »
Washing a solution is precisely like extracting it, only that you discard the washing as opposed to keeping it when you extract.

Separatory Funnel Extraction Procedure

(http://orgchem.colorado.edu/hndbksupport/ext/extprocedure.html)

hypo

  • Guest
jeezus!!
« Reply #2 on: October 18, 2003, 06:49:00 PM »
don't post your friggin' ICQ number for gods sake!!


Stonium

  • Guest
I removed it. Topdowner: Don't post personal...
« Reply #3 on: October 19, 2003, 04:09:00 AM »
I removed it.

Topdowner: Don't post personal information in the public forums.


hypo

  • Guest
thanks, stoni
« Reply #4 on: October 19, 2003, 10:37:00 AM »
he still has it in his other post though  ;)

i don't know much about those instant messanger thingies,
but don't they have a P2P mode, which would make it very
easy to find out his IP-address??

(i'm not suggesting he is harvesting IPs, but: one should never ever
contact any other bee over ICQ or IRC or things like that. (imho)
thanks to the PM function it's unecessary anyway, so no need to risk
it. (use common sense, people!))


topdowner

  • Guest
OK
« Reply #5 on: October 19, 2003, 12:45:00 PM »
I have understand what you said. But i have a new question. I want made 2,5 DMA and i must wash the solution (Consists of:2,5-dimethoxybenzaldehyde, Acetic Acid, Nitroethane and ammonium acetate) with Sodium Chloride. But the Salt will be dissolve in the solution. How can i extract the salt when its dissolved?

starlight

  • Guest
two layers
« Reply #6 on: October 19, 2003, 01:20:00 PM »
the salty water will form a separate layer from the nitroethane, 2,5DMBA, 2,5DMP2NP. After shaking, allow the layers to form, separate off the salty water layer and proceed to the next step of your procedure with the organic layer.

topdowner

  • Guest
Salty Layer
« Reply #7 on: October 19, 2003, 02:04:00 PM »
How can I recognize the salty layer??? i think, i write the part of the text which one i don´t understand!

"A solution of 10.0 g 2,5-dimethoxybenzaldehyde in 50 mL glacial acetic acid was treated with 6.8 g of nitroethane and 4.0 g of anhydrous ammonium acetate.  This mixture was heated on the steam bath for 3 h and then the reagent/solvent was removed under vacuum.  The residue was suspended in H2O and extracted with CHCl3.  Removal of the solvent from the pooled extracts yielded 11.2 g of an impure 1-(2,5-dimethoxyphenyl)-2-nitropropene which, on recrystallization from 75 mL boiling MeOH, gave 6.7 g of product with a mp of 73-75 deg C. Anal. (C11H13NO4) C,H,N.  This nitrostyrene has been periodically available commercially from a number of sources."

Nad how do i remove the solvent under vacuum?

please help me... ::)


Thanx

Flippie

  • Guest
extraction and washing
« Reply #8 on: October 19, 2003, 04:27:00 PM »
How can I recognize the salty layer???

You should really study some organic chemistry before SWIY starts to synthesize 2C-B. It's definately not the easiest synthesis to start with. You will encounter extraction and washing all the time while cooking. Master the theory on extraction and washing before you proceed, it will save you a lot of money on chemicals.

I can recommend James W. Zubrick's book "The Organic Chem Lab Survival Manual". I will give you some  free hints you can find in this excellent book.

I quote "

Never, never,never,never,
ever throw away any layer, until you are absolutely sure you'll
never need it again. Not very much of product can be
recovered from the sink trap!
"

This may sound silly but is is very useful!

I think it is better to call the "salty" layer the aqueous layer. [Extraction can only be done between two immiscible liquids, organic layer/aqueous layer] To know which layer floats on top you need to know what the density of your organic solvent is. The lighter layer floats on top of the heavier layer. Logic isn't it? You can assume that a dilute NaCl solution has the same density as pure water (about 1g/ml @25°C). Check the density of your organic solvent and you know if the layer will be on top or not.

An experimental way I quote directly from Zubrick's book:

""Which layer is the water layer?" This is so simple, it confounds everyone. Get a small (10x75 mm) test tube and add about 0.5-1.0 ml water. Now add 2-4 drops of the layer you thinks is aqueous, and swirl the tube. If the stuff doesn't dissolve in the water, it's not an aqueous (water) layer. The stuff may sink to the bottom, float on top, do both, or even turn the water cloudy! It will not however, dissolve."

Good luck and study hard!


Flippie

  • Guest
Removing solvent under vacuum
« Reply #9 on: October 19, 2003, 05:04:00 PM »
Nad how do i remove the solvent under vacuum?


Reading the question I think I can assume that you don't have a rotary evaporator (Rotovap). A Rotovap is commonly used to remove low boiling organic chemicals, usually solvents, from a mixture of compounds. The solvents or low boiling compounds are removed by a simple distillation. The Rotovap is designed to be operated under a vacuum (to lower a compound's boiling point) and to heat the sample at the same time. A cold finger is used to condense the vapors to a liquid, which are trapped in a separate flask.

Of course if you don't have a Rotovap, you could set up for vacuum distillation and use magnetic stirring to substitute for the rotation in a Rotavap.

The higher the vacuum the lower the boiling point of the solvent will be. You can calculate the boiling point of your solvent under vacuum using a Nomograph. Visit the following link on Rhodium's page for enlightment.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/equipment/nomograph.html



I don't have shares in Zubrick's book  ;) , but again I can recommend the book to gain understanding about several kinds of distillation techniques.

Buy the book man and study!


topdowner

  • Guest
Is it necessarily to wash the solution?
« Reply #10 on: October 19, 2003, 06:05:00 PM »
In the text is written "...wash the solution with NaCl and put it into the seperation funnel (used before) to wash it..." I think that I don´t have to wash it at all, or am I wrong?  ::)

starlight

  • Guest
i think you will find you are wrong
« Reply #11 on: October 19, 2003, 06:29:00 PM »
if it says to wash with NaCl solution, then that is what is meant to happen. You can't just go cutting out steps in a procedure and expect it to work. At best you will end up with a low yield, or impure product. At worst you will end up with nothing. Purification steps are incredibly important if you want to succeed.

Not being rude, but judging by the level of your questions, you will undoubtedly be unsuccessful with this synthesis unless you do some real learning first. As suggested, buy some books and start reading. Otherwise you will waste inordinate amounts of time and money.

Flippie

  • Guest
I think that I don´t have to wash it at all,...
« Reply #12 on: October 19, 2003, 06:31:00 PM »
I think that I don´t have to wash it at all, or am I wrong?

You are wrong. If your cooking book says to wash then you wash. Unless of course you are a very skilled cook with lots of experience and the capability to judge the necessity of a certain purification you'd better stick to the recipe.
You cannot skip every step you are not sure of! Take my advice first read and learn then start to cook, not the other way around!


topdowner

  • Guest
you´re right...!
« Reply #13 on: October 19, 2003, 06:36:00 PM »
Yes you´re right with that what you said.But i think to try goes studying over. Thanxx

topdowner

  • Guest
Has someone a pressure diagram of chloroform
« Reply #14 on: October 19, 2003, 06:38:00 PM »
If someone has it please reply.

Flippie

  • Guest
pressure diagram of chloroform
« Reply #15 on: October 19, 2003, 07:01:00 PM »
I don't think I know what exactly you understand as a "pressure diagram of chloroform".

I figure that you might want to know the boiling point of chloroform at a reduced pressure. The boiling point of chloroform at atmospheric pressure is 61.2°C. If you know the vacuum your pump pulls you can calculate the boiling point under vacuum using the nomograph.

If you meant something else, please clarify your question and I'll try to help you.


topdowner

  • Guest
nomograph
« Reply #16 on: October 19, 2003, 07:04:00 PM »
i don´t understand the nomograph. And we in Germany calculate with bar not torr. And the nomograph says me nothing. I can´t read this kind of diagram.

hypo

  • Guest
not true
« Reply #17 on: October 19, 2003, 07:07:00 PM »
> And we in Germany calculate with bar not torr

nah, german chemists use torr as often as others.


topdowner

  • Guest
red the nomograph
« Reply #18 on: October 19, 2003, 07:11:00 PM »
Can somebody help me to red the nomograph??? I don´t understand how to read it.

Flippie

  • Guest
nomograph
« Reply #19 on: October 19, 2003, 07:59:00 PM »
Conversion of bar to torr is easy:

1 atm = 1.013 bar = 1013 hPa = 760 torr (Torricelli :P )
Now 1 mm Hg = 1 torr, so you can easily find that
1 torr = 1.3 x 10-3 bar

Concerning the use of the nomograph I cannot explain it better than on Rhodium's site. Nevertheless in your case you cannot use the nomograph since the bp of chloroform at atmospheric pressure is below 100°C.
If you want to know more use Google and search on Clausius-Clapeyron equation (mathematical background of the nomograph).