Wednesday
August 20, 2014

Homework Help: Extraction equations

Posted by Sheryl on Saturday, October 7, 2006 at 9:24pm.

We did an extraction. A solid including benzoid acid, p-nitroaniline, and napthalene was dissolved in dichloromethane. HCl was added to give the aqueous salt of p-nitroanaline. NaOH was added to give the aqueous salt of benzoic acid. Napthalene remained. We then air dried them. I need to write equations for "every single compound and chemical". I also need to show solubility EACH TIME. Capitalization not mine. Here goes.

NO2-Benzene-NH2(s) + HCl(aq) --> NO2-benzene-NH3(s) + Cl-(s)

Benzene-COOH + NaOH --> benzene-COO-Na+(s) + H2O(l)

Napthalene remained in the organic solution and we air dried it. I don't know if I need to do anything with it.

Since we air dried everything, I'm not sure whether to put solid or liquid as the phase of matter.

Thanks for your help,

Sheryl


I think I would make a flow chart. I have a question about the procedure. When treated with NaOH, the benzoic acid formed the Na salt. What did you do next? Was that soluble in water? Did you do anything to regenerate the benzoic acid or did you leave it as the Na salt? At what point did you get a solid and filter?


I'm going to make a flow chart as best I can.
Solid benzoic acid, p-nitroaniline and napthalene ->
Dissolve in CH2Cl2 ->
Add HCl. Reaction produces R-NH3+Cl- in water layer. Repeat extraction ->
Add NaOH to organic layer. Reaction produces R-COO-Na+ + H2O in water layer. Repeat extraction ->
Wash organic layer twice. (H2O added.) ->
Add anhydrous sodium sulfate to organic layer to dry it. ->

Recovery of each compound.

Add Na2SO4 ro organic layer CH2Cl2 to dry it. Let it evaporate after filtering. (CHCl2 + napthalene) ->
Add NaOH to nitroaniline to neutralize. Filter and let dry. ->
Add HCl to benzoic acid to neutralize. Filter, wash with cold water, and let air dry.


So here are my new equations of the procedure

R-NH2(s) + HCl(aq) -> R-NH3+Cl-(s)

R-COOH(s) + R-COO-Na+(aq) -> + H2O(l)

CHCl2(l) + H2O(l) -> CHCl2(l) + H2O(l) Probably don't need this equation as no reaction.

Don't know whether to use solid on R-NH2 and R-COOH as they are dissolved when the interact with HCl and NaOH

H2O(l) + Na2SO4(s) -> 2NaOH(s) + H2SO4(s)

R-NH3+Cl-(aq) + NaOH(aq) + HCl(aq) -> R-NH2(s) + NaCl(s) + H2O(l)

R-COO-Na+(aq) + NaOH(aq) + HCl(aq) -> R- COOH(s) + NaCl(s) + H2O(l)


Hope this is understandable.
Sheryl



The NaCl in the last two equations should be in aqueous phase.


I think you need equations at each step of the flow chart and show what is in the dichloromethane layer and what is in the aqueous layer. If you do that, you avoid,
a. trying to guess as to exactly what you teacher wants when she says ALL THE SOLUBILITIES.
b. trying to know if you should write solid when it really is in the aq phase.

Show what is in the aq phase and what is in the orgnic phase, what is in solution and what isn't etc. Just keep drawing arrows down for each step of the process. I tried to draw one last night and failed to do so on the computer. I think, however, that you have address part of the problem I had with your first answer; i.e., you didn't have all the steps then.


Extraction procedure and equations:

Solid benzoic acid, p-nitroaniline and napthalene ->
Dissolve in CH2Cl2 ->
Organic layer: CHCl2 (l) + napthalene(aq)
Future aqueous layer: R-COOH(aq) + R-NH2

Add HCl. Reaction produces R-NH3+Cl- in aq. layer. Repeat extraction ->
Organic layer: CHCl2 (l) and napthalene(aq)
Aqueous layer: RNH3+Cl-(aq) and R-COOH(aq)
Reaction: R-NH2(aq) + HCl(aq) --> R-NH3(aq) + Cl-(aq)

Add NaOH to organic layer. Repeat extraction ->
Organic layer: CHCl2 and napthalene
Aqueous layer: R-COOH-Na+ and H2O
Reaction: R-COOH(aq) + NaOH(aq) --> R-COO-Na+ + H2O(l)

Recovery of each compound:
Napthalene: Wash organic layer twice. (H2O added.) ->
Organic layer: CH2Cl2 and H2O and napthalene
Add anhydrous sodium sulfate (Na2SO4) to organic layer (CH2Cl2) to dry it. ->
Reaction: Na2SO4((aq) + H2O(l) --> 2NaOH(s) + H2SO4(s)
Let it evaporate after filtering solids to retrieve napthalene.

Add NaOH to the nitroaniline solution to neutralize. Filter and let dry. ->
Aqueous solution: NaOH and R-NH3+Cl-
R-NH3+Cl-(aq) + NaOH(aq) -> R-NH2(s) + NaCl(aq) + H2O(l)

Add HCl to R-COO-Na+ to neutralize. Filter, wash with cold water, and let air dry.
Aqueous layer: R-COO-Na+ and HCl and H2O? ?R-COO-Na+(aq) + HCl(aq) -> R-COOH(s) + NaCl(aq)

Is this any better? Apparently I'm not very organized.

Sheryl??


Extraction procedure and equations:

Solid benzoic acid, p-nitroaniline and napthalene ->
Dissolve in CH2Cl2 ->
Organic layer: CHCl2 (l) + napthalene(aq)
Future aqueous layer: R-COOH(aq) + R-NH2

I would write CH2Cl2(l) + solution of naphthalene(note spelling of naphthalene), NO2benzeneNH2, and RCOOH. And naphthalene CAN'T be (aq). It isn't anywhere close to water yet. I would forget about the future in this step. Write about it when you get there. Then I would make a + sign below that, write HCl below the + sign, then make two arrows pointing down. Make one of them diagonal to the left, like this / and the other one diagonal pointing to the right\. Now you are ready to write the reactions that took place upon the addition of HCl.

Add HCl. Reaction produces R-NH3+Cl- in aq. layer. Repeat extraction ->
Organic layer: CHCl2 (l) and napthalene(aq)
Aqueous layer: RNH3+Cl-(aq) and R-COOH(aq)
Reaction: R-NH2(aq) + HCl(aq) --> R-NH3(aq) + Cl-(aq)

Below the left arrow, write aqueous layer. Below the right arrow write organic layer (or CH2Cl2 layer). Below the left arrow write the reaction that takes place with NO2benzeneNH2.
NO2benzeneNH2(s) + HCl(aq) ==>NO2benzeneNH3^+(aq) + Cl^-(aq). Note the NO2benzeneNH2(s) is NOT (aq) here, unless, of course, it dissolves in water, and I don't think it does. Note that I wrote p-nitroaniline as (s) but I am unsure what to do. It is a solid normally but it is dissolved in the organic phase at this point. Perhaps NO2benzeneNH2(org) + HCl(aq) ==> NO2benzeneNH3^+(aq) + Cl^-(aq).
Now switch to the right arrow and write "solution of RCOOH and naphthalene in CH2Cl2." Note these do not carry an (aq) since they are in the organic phase and CAN'T be aqueous.


Add NaOH to organic layer. Repeat extraction ->
Organic layer: CHCl2 and napthalene
Aqueous layer: R-COOH-Na+ and H2O
Reaction: R-COOH(aq) + NaOH(aq) --> R-COO-Na+ + H2O(l)
Below the "solution of RCOOH and naphthalene in CH2Cl2 layer" write a + sign, below that NaOH and below that two arrows pointing down. One diagonal / and one diagonal \. Below the left one write the reaction that takes place with the RCOOH.
RCOOH(s) + NaOH(aq) ==> RCOONa(aq) + H2O(l). Again, I am unsure about the s for RCOOH. Perhaps RCOOH(org) would be better, I just don't know. Note also that since we are writing NaOH as NaOH(aq) and HCl as HCl(aq),(instead of aq ions) we might dispense with writing NO2RNH3Cl as NO2RNH3^+(aq) + Cl^-(aq) and just write it as NO2RNH3Cl(aq). That is really a matter of preferance and I don't know what your teacher wants. Same thing about RCOONa(aq) versus RCOO^-(aq) + Na^+(aq). Now switch to the right arrow and write "solution of naphthalene in CH2Cl2"
Note that each step has a + sign, a reagent added, then two diagonal arrows pointing down but different directions, as / and \, then a statement about the phase or a reaction. Each time you have a step, you get the + sign, a reagent (or a step such as filter), and two arrows. Each arrow splits multiple times. We are getting so many arrows at this point that it will be confusing to continue but I hope you get the idea from this.I have some notes below but this is the end of my flow sheet part.

Recovery of each compound:
Napthalene: Wash organic layer twice. (H2O added.) ->
Organic layer: CH2Cl2 and H2O and napthalene
Add anhydrous sodium sulfate (Na2SO4) to organic layer (CH2Cl2) to dry it. -

Reaction: Na2SO4((aq) + H2O(l) --> 2NaOH(s) + H2SO4(s) Isn't the Na2SO4 a solid? Does it REALLY produce NaOH and H2SO4 or does it just form a hydrate of Na2SO4?
Let it evaporate after filtering solids to retrieve napthalene.

Add NaOH to the nitroaniline solution to neutralize. Filter and let dry. ->
Aqueous solution: NaOH and R-NH3+Cl-
R-NH3+Cl-(aq) + NaOH(aq) -> R-NH2(s) + NaCl(aq) + H2O(l) Be consistent with RNH3^+(aq) + Cl^-(aq) or as RNH3Cl(aq).

Add HCl to R-COO-Na+ to neutralize. Filter, wash with cold water, and let air dry.
Aqueous layer: R-COO-Na+ and HCl and H2O? ?R-COO-Na+(aq) + HCl(aq) -> R-COOH(s) + NaCl(aq)
RCOONa(aq) + HCl(aq) ==> NaCl(aq) + RCOOH(s)


Thanks. I know that was a lot of effort because I'm still looking at it.

Test on Thursday. Hope I pass.

Sheryl


Extraction procedure and equations:

Solid benzoic acid, p-nitroaniline and napthalene ->
Dissolve in CH2Cl2 ->
Organic layer: CHCl2 (l) + napthalene(aq)
Future aqueous layer: R-COOH(aq) + R-NH2

Add HCl. Reaction produces R-NH3+Cl- in aq. layer. Repeat extraction ->
Organic layer: CHCl2 (l) and napthalene(aq)
Aqueous layer: RNH3+Cl-(aq) and R-COOH(aq)
Reaction: R-NH2(aq) + HCl(aq) --> R-NH3(aq) + Cl-(aq)

Add NaOH to organic layer. Repeat extraction ->
Organic layer: CHCl2 and napthalene
Aqueous layer: R-COOH-Na+ and H2O
Reaction: R-COOH(aq) + NaOH(aq) --> R-COO-Na+ + H2O(l)

Recovery of each compound:
Napthalene: Wash organic layer twice. (H2O added.) ->
Organic layer: CH2Cl2 and H2O and napthalene
Add anhydrous sodium sulfate (Na2SO4) to organic layer (CH2Cl2) to dry it. ->
Reaction: Na2SO4((aq) + H2O(l) --> 2NaOH(s) + H2SO4(s)
Let it evaporate after filtering solids to retrieve napthalene.

Add NaOH to the nitroaniline solution to neutralize. Filter and let dry. ->
Aqueous solution: NaOH and R-NH3+Cl-
R-NH3+Cl-(aq) + NaOH(aq) -> R-NH2(s) + NaCl(aq) + H2O(l)

Add HCl to R-COO-Na+ to neutralize. Filter, wash with cold water, and let air dry.
Aqueous layer: R-COO-Na+ and HCl and H2O? ?R-COO-Na+(aq) + HCl(aq) -> R-COOH(s) + NaCl(aq)

Is this any better? Apparently I'm not very organized.

Sheryl??


Hello! Good Site! Thanks you! jgyknhvjeqvdi

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