Saponification of unknown: In a 100 mL single neck RBF, water (50 mL), the unkno

Question

Saponification of unknown: In a 100 mL single neck RBF, water (50 mL), the unknown (x g, y mmol and a stoichiometric amount of potassium hydroxide (x g, y mmol) were combined. The reaction was refluxed for 2 hours, and cooled to room temperature. The water mixture was then extracted with diethyl ether (2 x 25 mLJ. The ether was discarded, and then the water layer was acidified using excess concentrated HCl (5 mL). The water layer was then extracted a second time with diethyl ether (2 x 25 mL), and the ether extracts dried over using magnesium sulfate. Removal of the volatile solvent, yielded the desired product (xg, 75.9%) Heptanoic Acid The unknown is Heptanoic Acid (C7H1402). The mass of the unknown is 3 grams. CH HO

Explanation / Answer

To 3 g of unknown ester was added stoichiometric amount of KOH. the reaction was refluxed and then extracted with diethyl ether to remove any unrescted ester. The aqueous layer left behind is acidified to reform neutral acid which is than extracted with diethyl ether. Drying the organic layer over anhydrous MgSO4 and then solvent removal yields heptanoic acid.

The ester is thus of structure heptanoic as the backbone structure.

1 mole ester + 1 mole KOH ---> 1 mole carboxylic acid + 1 mole water

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