Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: rubymelia on 23/11/2018 17:56:36

Title: Why would you need to acidify to pH 2 during an experiment?
Post by: rubymelia on 23/11/2018 17:56:36
I am reacting 6-APA and Toluoyl Chloride in the presence of NaHCO3 to produce a penicillin derivative. After separating the solution using n-buytl acetate (to remove the excess organic Toluoyl Chloride) I need to acidify the solution using 5M aqueous H2SO4 to pH 2 but I don't understand why? Any thoughts? The acidification process leads to the solid product.
I have completed a mechanism for this reaction however can't see how the acid comes into play.

Thanks for any suggestions.
Title: Re: Why would you need to acidify to pH 2 during an experiment?
Post by: Bored chemist on 23/11/2018 18:03:47
What is the product of the reaction?
Would it react with NaHCO3?
Title: Re: Why would you need to acidify to pH 2 during an experiment?
Post by: rubymelia on 23/11/2018 18:08:11
What is the product of the reaction?
Would it react with NaHCO3?
I have attached the structure of the product. I am assuming the acid is to do with extracting the product as the solid is formed on adding the acid?
Title: Re: Why would you need to acidify to pH 2 during an experiment?
Post by: chiralSPO on 23/11/2018 19:28:42
The desired product is a carboxylic acid. At pH values more basic than pH of 3, a significant fraction of the product will be deprotonated, as the carboxylate ion, which is likely to be quite soluble in water. By moving the pH down to 2, one can limit the fraction that exists as the carboxylate to less than one part per thousand, increasing the yield, and precipitating the insoluble acid from water.