These questions must be answered in addition to your typed post-lab report. This

Question

These questions must be answered in addition to your typed post-lab report. This count towards your participation grade. Short bullet point answers are sufficient. Please attach this paper to your lab report. 1. Explain what happens to your carboxylic acid (base extract) from the first step (dissolve in ether) to the last step Dry on watch glass. (i.e. gets deprotonated by what, reprotonated by what. has affinity for what?) 2. Does your neutral organic undergo any structural changes during the experiment? Why, why not? 3. The melting point of your neutral organic cannot be determined (thermometer exploded before compound melted. What happened? 4. Your carboxylic acid has a melting point range of 130-145 *C. Also you have a "phenomenal" yield of 101%. What is going on? How can you fix it?

Explanation / Answer

1. Carboxylic acid reacts with added base NaHCO3(aq) for form sodium carboxylate salt which dissolves in water. The water layer is then separated and protonated by acidification with HCl to reform carboxylic acid compound from the solution. The compound is extracted in ether. The ether layer containing the carboxylic acid is evaporated to dryness to isolate the carboxylic acid.

2. The neutral organic substrate does not undergo any change under these conditions since it does not have any reactive functional groups present on the compound structure.

3. If the thermometer notch is blocked (in the apparatus), a pressure is developed as we start to heat the system. It leads to explosion at higher temperatures.

4. The carboxylic acid may have adsorbed water in it which would increase the weight of the final product and thus higher percent yields are obtained. The compound thus must be thoroughly dried under vacuum prior to melting point measurement and percent yield calculations.

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