Molecule 5-methylhept-3-ynoic acid ssignment 5: Separation Scheme Correction On

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Molecule 5-methylhept-3-ynoic acid

ssignment 5: Separation Scheme Correction On a page titled Incorrect Separation Scheme print the incorrect separation scheme provided for your molecule on Blackboard. The top of the separation scheme shows what other compound is mixed with your molecule. Assume for the purposes of this assignment that both compounds are solid at room temperature. Also assume that both compounds are soluble in ether, except ionic compounds. The goal of the separation is the isolate each of the two compounds from the mixture. Below the incorrect separation scheme write a discussion of this incorrect scheme identifying all of the mistakes in the separation scheme. Keep in mind that there o will be more than one mistake in the scheme For each mistake, give a detailed, scientific explanation of why it is incorrect. All answers must be typed. No handwritten responses will be accepted. o o On a page titled Correct Separation Scheme draw using a chemical drawing program or other computer generated form, a correct separation scheme to isolate your molecule from the provided second molecule. Make sure to indicate the phase of each chemical in every step (s, l, g, aq) and write the separation technique used in each step (ie: vacuum filtration). The list below gives the reagents available in the lab. Use any of the reagents below to isolate the compounds. Remember that the simplest separation scheme is the best one. Try to avoid unnecessary steps. No hand drawn structures will be accepted. H2O H3PO4 10% aqueous NaOH 5% aqueous NaHCO3 6M HCI 5% HCI Diethyl ether (ether) CH;OH .anhydrous Na2SO4 us MgSO4 Saturated NaCl Sodium borohydride (NaBH4 NaCl solid ithium aluminum hydride (LiAlH4)

Explanation / Answer

Addition of 5% NaHCO3 to the mixture of the organic acid and naphthalene in ether separates the analytes into two phases. The sodium salt of the acid goes into the aqueous phase while the ether layer contains naphthalene.

Treatment of the aqueous layer with 6 M HCl precipitates out a solid. The solid is he organic acid. An organic acid is insoluble in aqueous acid, since there are no acid-base reactions to solubilize the organic acid. Vacuum filtration of the aqueous solution separates out the acid as a solid residue. NaCl, being highly water soluble, goes into the aqueous layer.

The ether layer is treated with anhydrous MgSO4 to remove traces of moisture. The ether is then evaporated to give solid naphthalene.

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