The mole ratio of acid and alcohol will depend on your previous yield (In this p

Question

The mole ratio of acid and alcohol will depend on your previous yield (In this procedure you will use the benzoic acid that you prepared and methanol is used in excess. A 1: 10 molar ratio should suffice, once again use conc. sulfuric acid as a catalyst): 1.0 ml of sulfuric acid for every 4.0 ml of methanol. The esterification reaction will require of a 60' reflux, or five minutes in the microwave. After the reflux (or microwave) you need to purify the ester, and this can be done using a liquid-liquid extraction. Review previous labs and have a flow chart ready to indicate how will you purify the ester from the non-reacted benzoic acid, the catalyst, and the excess methanol Results: Mass of bromobenzene Mass of Magnesium Mass of Benzoic acid dry Mass of benzoic acid used in the esterification Theoretical Yield Mass of methyl benzoate obtained Percentage Yield IR (interpreted directly on the spectrum) At this stage of your multistep synthesis the amount of product is considerably less than the prescribed recipe. The reaction will be scaled down accordingly, most of you will have to carry it down in small test tubes, it can be done. The secret for success is once again perfectly dried glassware, since water interferes with the formation of the nitronium ion. Results: Mass of Bromobenzene Mass of Magnesium Mass of methyl benzoate Mass of methyl -3-nitrobenzoate crude Mass of methyl-3-nitrobenzoate recrystallized Theoretical Yield Percentage Yield from methyl benzoate Percentage overall yield from bromobenzene (you can calculate this using the percentages of the indivisual reactions) Mp of product IR (interpret directly on the spectrum)

Explanation / Answer

Esterification and separation

Esterification of benzoic acid with methanol in acid catalyst

Separation steps

1. Wash the reaction mixture with 10% NaHCO3 (aq) two or three times. Check the pH of aqueous wash, it has to be neutral when all the catalyst is washed off.

2. Remove the solvent on rotary evaporator

3. Distill the crude ester product using high vacuum pressure.

4. weigh the final pure ester.

Nitration of methylbenzoate

steps

1. first prepare nitrating agent by mixing appropriate amount of nitric acid and sulfuric acid toegther

2. the reagent is then added to methylbenzoate previously dissolved in a solvent.

3. let the reaction run and once done, wash the reaction mixture with aq. NaHCO3 solution to clear acid from the solution.

4. separate the organic layer from aqueous layer.

5. Dry the organic layer and filter

6. remove solvent on rotary evaporator to isolate the pure product

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