August 10, 2022, 08:09:04 AM
Forum Rules: Read This Before Posting


Topic: Separating Aspirin and salicylic acid  (Read 9916 times)

0 Members and 1 Guest are viewing this topic.

Offline johnj7

  • Regular Member
  • ***
  • Posts: 23
  • Mole Snacks: +0/-0
Separating Aspirin and salicylic acid
« on: February 12, 2008, 01:17:43 AM »
Hello, i'm struggling with another extraction problem

The problem states:
"Data for solubility for 1 g of aspirin or salicylic acid:
Aspirin - 300 mL of H20, 17 mL of chloroform, 12 mL of ethyl ether
Salicylic acid - 460 mL of H20, 42 mL of chloroform, 3 mL of ethyl ether.

If you had a mixture of equal weights of aspirin and salicyclic acid, which solvent pair (ether-water) or (chloroform-water) would give the most efficient extraction.  Why?"

I orginally thought that the answer was ether-water.  I first calculated the partition coefficients for each solvent pair.  Then I saw that the ether-water partition coefficients were larger, and so thought that ether-water would give the most efficient extraction. 

However, the answer states:  "Chloroform-water.  Neither will be very good because both aspirin and salicylic acid will largely extract into the organic phases in all cases.  However, the chloroform-water system elaves mroe in the aqueous phase and thus allows a better separation.  A different means of purifying the compounds is needed." 

Could someone help me out/help understand what's going on?

Thanks

Offline Transmutation

  • Regular Member
  • ***
  • Posts: 13
  • Mole Snacks: +0/-1
Re: Separating Aspirin and salicylic acid
« Reply #1 on: February 29, 2008, 04:11:58 AM »
Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin.  :P

Offline ARGOS++

  • Sr. Member
  • *****
  • Posts: 1489
  • Mole Snacks: +199/-56
  • Gender: Male
Re: Separating Aspirin and salicylic acid
« Reply #2 on: March 05, 2008, 08:55:54 PM »

Dear Johnj7;

Let’s give you the results first:
   In this particular case, your decision from your stomach is:     Right!
   In this particular case, the other argumentation is completely: Wrong!
   In this particular case, your own argumentation is also:          Wrong!   

How would you define “Efficiency” for such an Extraction?
    Hint:  Which Phase would you collect?

Recipe for visualisation:
With your new definition in mind, put 10.0 g ASA and 10.0 g SA together, and extract/calculate the Extraction following:  "Solubility Problem (Extraction!)”,  –   and be surprised!
 

Good Luck!
                    ARGOS++

Offline agrobert

  • Chemist
  • Full Member
  • *
  • Posts: 629
  • Mole Snacks: +69/-17
  • Gender: Male
  • diels alder
Re: Separating Aspirin and salicylic acid
« Reply #3 on: March 05, 2008, 09:06:02 PM »
Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin.  :P

How is this a separation?
In the realm of scientific observation, luck is only granted to those who are prepared. -Louis Pasteur

Offline ARGOS++

  • Sr. Member
  • *****
  • Posts: 1489
  • Mole Snacks: +199/-56
  • Gender: Male
Re: Separating Aspirin and salicylic acid
« Reply #4 on: March 07, 2008, 12:13:43 PM »

Dear Agrobert;

   How true!,  –    Maybe a young “Colt”.


Good Luck!
                    ARGOS++


Offline minimal

  • Regular Member
  • ***
  • Posts: 83
  • Mole Snacks: +1/-0
Re: Separating Aspirin and salicylic acid
« Reply #5 on: March 07, 2008, 01:15:14 PM »
Or you could just convert the salicylic acid into aspirin with acetic anhydride and potassium carbonate.  Then could recrystallize pure aspirin.  :P

How is this a separation?

It's not, he was just making a joke, on the assumption you're separating in order to obtain the ASA.

Offline ARGOS++

  • Sr. Member
  • *****
  • Posts: 1489
  • Mole Snacks: +199/-56
  • Gender: Male
Re: Separating Aspirin and salicylic acid
« Reply #6 on: March 07, 2008, 02:12:09 PM »

Dear Minimal;

I never interpreted it different, or as something else.


Good Luck!
                    ARGOS++

Sponsored Links