DAT Destroyer OC #3

[pawprints8]

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[Mrhyde]

Question #3 asks which solvent should be used to extract molecule A (benzoic acid) and molecule B (ethyl benzene).
I understand that a base is needed to extract the acid, so two answers remain:
EtOH/H2O at pH=10
(C2H5)O/H2O at pH=10

The solution states that the first answer is incorrect because "the two solvents cannot be miscible with each other." However, ethanol and water are indeed miscible due to their mutual ability to hydrogen bond. Please let me know if perhaps this question could be answered with both Et/OH/H20 and (C2H5)O/H2O to extract benzoic acid from a mixture with ethyl benzene.

Thanks!

Dont over think this question. By the way as a side question, have you seen Chads videos ? I only ask this because he covered this particular topic and question pretty well so it might benefit you to check out that video lesson on course saver.

For this question we see we have COOH and C2H2 well the only thing we can do if we have these two mixed is separate them into layers, but how? Well we see that COOH has an H so if we find a way to remove that H then we will have one go to an ether layer and one into a water layer where we can filter one out and then protonate back the H and then boil since ether has a low boiling point, to get everything separated.

To remove an H from COOH would be terrible in a soultion of excess H's which is what a low ph acidic solution is. So we choose a HIGH ph which has a bunch of OH floating in it instead. Then we see we have C2H5OH vs (C2H5)2O well its best to choose (C2H5)2O since it has an open 'O' at the end which has room to attach the H we want to remove thus D is the best answer.

 

[DAT Destroyer]

Question #3 asks which solvent should be used to extract molecule A (benzoic acid) and molecule B (ethyl benzene).
I understand that a base is needed to extract the acid, so two answers remain:
EtOH/H2O at pH=10
(C2H5)O/H2O at pH=10

The solution states that the first answer is incorrect because "the two solvents cannot be miscible with each other." However, ethanol and water are indeed miscible due to their mutual ability to hydrogen bond. Please let me know if perhaps this question could be answered with both Et/OH/H20 and (C2H5)O/H2O to extract benzoic acid from a mixture with ethyl benzene.

Thanks!

No,,,,in an extraction,,,we need to have two distinct layers. The organic compound would dissolve in the ether....not in ethanol. Recall that ethers are able to dissolve organic compounds. If you had the alcohol layer in lieu of the ether...the hydrocarbon would not be able to dissolve

Hope this helps.

Dr. Romano