Fisher Esterification of m-nitrobenzoic acid to produce methyl-m-nitrobenzoate

Calculations: See notes above for the amount of reagent we are planning to use in this experiment. (2/15 points)

Limiting reagent â identify if nitric acid or benzoic acid is the limiting reagent for this reaction. Use the molar concentration of nitric acid to calculate the number of mols of this reagent.

Theoretical yield â calculate how much is expected to be formed of your product

WE will be using 1.5g of m- nitrobenzic acid , 12ml methanol, 0.6ml concentrated H2SO4.

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Jamar FerryLv2

6 Jul 2019

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I am having great difficulty with the calculations! Please help! I am needing limiting reagent, moles of limiting reagent, moles of methyl benzoate isolated, theoretical yield in moles and grams and percent yield! The procedure is for Methyl Benzoate by Fischer Esterification, it is the following:

1. Place 10.0 g of benzoic acid and 25 mL of methanol in a 100-mL round bottomed flask. In the fume hood, pour 3 mL of concentrated sulfuric acid slowly and carefully down the walls of the flask, and then swirl to mix the components.

2. Attach a reflux condenser, add a boiling stone, and reflux the mixture gently for 1 hour.

3. Cool the solution and decant into a separatory funnel containing 50 mL of water, and rinse the flask with 35 mL of diethyl ether. Add this ether to the separatory funnel, shake thoroughly, and drain off the water layer, which contains the sulfuric acid and the bulk of unreacted methanol.

4. Wash the ether in the separatory funnel with 25 mL of water followed by 25 mL of 5% sodium bicarbonate to remove any remaining traces of sulfuric acid and unreacted benzoic acid. Again shake, with frequent release of pressure by inverting the separatory funnel and opening the stopcock, until no further reaction is apparent; then drain off the bicarbonate layer into a beaker. If this aqueous material is made strongly acidic with hydrochloric acid, unreacted benzoic acid may be observed.

5. Wash the ether layer in the separatory funnel with saturated sodium chloride solution and dry the solution over anhydrous magnesium sulfate so that it no longer clumps together on the bottom of the flask. After 10 minutes, decant the dry ether solution into a flask, wash the drying agent with an additional 5 mL of ether, and decant again. Remove the ether using the rotary evaporator.

Limiting reagent _______________________________

moles of limiting reagent _______________________________ moles

g of methyl benzoate isolated _______7.95______ g ______________ moles

Theoretical Yield of methyl benzoate _____________ g ______________ moles

% Yield: _____________ %

Weights

anthranilic acid ___.33 g__________

sodium nitrite _________.6 g____

2-naphthol _______.13 g______

isolated azo compound ____.13 g_________

isolated salicylic acid _____.12 g________

1) Show your calculations for determining the proper amount of sodium nitrite to use.

2) What is your percent yield of salicylic acid? Show your calculations.

3) What is your percent yield of the azo compound that you isolated (2-[(2-hydroxy-1-naphthalenyl)azo]benzoic acid). Show your calculations.

4) Why does the dimethyl aniline couple with the diazonium salt at the para postion of the ring?

OUR PROFESSOR GAVE US SOME SOME HINTS AND A EXAMPLE ON HOW TO SOLVE THIS

1) Determine the mols used of anthranilic acid and sodium nitrite in preparation of the diazonium salt. Whichever one of those, either anthranilic acid or sodium nitrate, is the limiting reagent, you're going to assume that's how many mols of the diazonium salt you prepared. For example, let's pretend anthranilic acid was my limiting reagent with 0.001 mols of it prepared (a bogus number for this example). I will assume then that I prepared 0.001 mols of diazonium salt.

To determine the % yield of salicylic acid, I need to determine how much of the diazonium salt was used in the reaction. To do so, I need to look at volume of diazonium salt used in this reaction. I'll give you heads up , it's 7 mL! How did I come to that conclusion? Well the diazonium salt was prepared by mixing 10 mL of HCl and 2 mL of H2O, totaling 12 mL. Of that 12 mL , 1 mL was used for methyl red and 4 mL was used for the azo compound reaction. This leaves me with a total of 7 mL used in the salicylic acid reaction. So 7/12 of the 0.001 mols was used to prepare salicylic acid. Knowing this will help you determine the theoretical yield of salicylcic acid. Your actual yield is the salicylic acid obtained.

To determine the % yield of the azo compound, you will need to do the same things as above. How much diazonium salt was used in this reaction? 4/12 (see above for my breakdown). Now this one is a little messier, because, you'll need to compare moles used of diazonium salt to mols of 2-naphthol. Whichever of those two players is the limiting reagent should be considered when determining theoretical yield. Your actual yield is the azo compound obtained.