Aspirin

If you prepare the stock of salicylic acid as indicated above, what is the concentration of your 100mL initial stock solution? What color is the solution in the flask? 0.08 grams SA 138.121 = molar mass of SA

0.08 g SA * 1 mol SA/138.121 g SA = 0.0005792 mol SA 0.0005792 mol SA/.100 L = 0.005792 M stock solution or 5.792 * 10-3 M The color of the solution is colorless.

Using a Spectrometer Aspirin

1. Blank spectrometer by filling cuvette 3/4 full with Fe(No3)3 (usually use distilled water but since Fe(No3)3 has a slight color, we are using this) 2. Make sure clear side of cuvette faces light. 3. Rinse blank cuvette twice with small amounts of stock solution. Fill cuvette 3/4. Find peak, get the maximum wavelength. 4. Collect absorbances for all dilutions at the max wavelength. 5. Graph to get best fit line

Aspirin Analysis Standard Curve Creation

1. Make the initial stock solution by adding 0.080 salicylic acid, 5 mL of ethanol. Dilute to 100 mL of water using distilled water. Calculate concentration 2. Take 2 mL of solution from 1 and dilute to volume with iron 3 nitrate to 25 mL. Calculate concentration Initial Stock Solution: 0.005864 M Final Stock Solution: 0.00047616 M 3. Make dilutions after making sure absorbance of stock solution is not higher than 1.0

Aspirin Synthesis General Procedure

1. Measure out 2.0 grams of salicylic acid and add it to an Erlenmeyer flask.Add 5.0 mL of acetic anhydride and 5 drops of 85% phosphoric acid. 2. Swirl mixture. Heat plate on hot plate at 75, swirling occasionally. Add 2 mL of distilled water after 10 min. Continue heating for 5 min. 3. When there are no more vapors, remove flask from hot plate and add 20 mL of distilled water. Allow reaction to cool near room temp. 4. While waiting for mixture to cool, set up Buchner funnel and filter flask. 5. Transfer flask to ice bath for 5 min, crystals of aspirin should form 6. Filter flask using Buchner funnel. When most of liquid is drawn through funnel, shut off suction and wash crystals with 5 mL of cold DI water. After 15 sec, turn on suction. 7. Wash the crystals like this 2 more times. 8. Weigh crystals and calculate a percent yield.

Aspirin Synthesis Analysis Procedure

1. Synthesize aspirin. 2. Mix aspirin with iron solution. Fe(NO3)3 reacts with salicylic acid to turn SA purple. 3. Then we will use absorption spectroscopy to determine amount of SA in aspirin sample. .

It is proposed to use 2.0g of C7H6O3 with 5mL of C4H6O3 (ρ = 1.087 g/mL) to perform the reaction. A. How many moles of each reactant are you starting with? B. What is the limiting reagent? C. Based on these calculations, how much product would you expect to obtain (theoretical yield)?

A. 2.0 g C7H6O3 * (1 mol C7H6O3)/(7(12.01)+6(1.01)+3(15.9994)) = 0.0145 mol C7H6O3 5 mL of C4H6O3 * (1.087 g/mL) *(1 mol C4H6O3)/(4(12.01)+6(1.01)+3(15.9994)) = 0.0532 mol C4H6O3 B. C7H6O3 + C4H6O3 → C9H8O4 + C2H4O2 0.0145 mol C7H6O3 * (1 mol C9H8O4 )/(1 mol C7H6O3) = 0.0145 mol C9H8O4 0.0532 mol C4H6O3 * (1 mol C9H8O4 )/(1 mol C4H6O3) = 0.0532 mol C9H8O4 C7H6O3 is the limiting reactant as it theoretically yields a lower amount of product. C. Based on these calculations: 0.0145 mol C7H6O3 * (1 mol C9H8O4 )/(1 mol C7H6O3) = 0.0145 mol C9H8O4 0.0145 mol C7H6O3 * (1 mol C2H4O2)/(1 mol C7H6O3) = 0.0145 mol C2H4O2 0.0145 mol C9H8O4 * (9(12.01)+8(1.01)+4(15.9994) g C9H8O4 ) = 2.61 g C9H8O4 or ASA 0.0145 mol C2H4O2 * (2(12.01) + 4(1.01) +2(15.9994)) = 0.871 g C2H4O2

Assume that you use the procedure above to work up your own aspirin sample. Assuming the equation from your standard curve is y = 1858.9x, answer the following questions: A. If the absorbance you obtain for Solution #2 is 0.145, what is C2? B. Calculate C1. C. Using C1, calculate how many grams of salicylic acid are present (MW = 138.123 g/mol). D. What is the percent purity of this sample?

Absorbance = 1858.9(Concentration) Absorbance = 1858.9(C2) C2 = 0.0000780 M = 7.80 * 10-5 M Calculate C1. Molarity of C1 * Volume of C1 = Molarity of C2 * Volume of C2 M1V1 = M2V2 (M)(0.001) = (0.0000780)(0.025) M1 = 0.00195 M = 1.95 * 10-3 M Using C1, calculate how many grams of salicylic acid are present (MW = 138.123 g/mol). 0.00195 M = x mol/0.025 L x = 4.875 * 10-5 mol 4.875 * 10-5 mol SA * (138.123 g/mol SA) = 0.006733 g SA = 6.73 * 10-3 g SA What is the percent purity of this sample? Percent purity = present grams of salicylic acid / g of sample = (6.73 * 10-3 g SA)/(0.10) = 0.06733 = 0.06733 * 100% = 6.73% is the percent purity

How does aspirin work?

Aspirin reduces production of prostaglandings which are responsible for pain, fever, redness swelling, etc. SO aspirin relieves these issues. It also reduces the production of substances involved in the blood clotting mechanism --> reduce risk of cardiovascular disease

Chemical formula of this drawing 2

C2H4O2

Aspirin Synthesis Equation: acetic anhydride with salicylic acid in the presence of an acid catalyst

C7H6O3 + C4H6O3 → C9H8O4 + CH3COOH Salicylic Acid + Acetic Anhydride --> Acetylsalicylic Acid + Acetic Acid

Chemical formula of this drawing

C9H8O4

Calculation of Percent Yield for Aspirin Actual Yield: 2.509 g

Equation: C7H6O3(s)+ C4H6O3(l)→ C9H8O4 (s) + C2H4O2(l) Theoretical Yield: 2.057 g C7H6O3 * (1 mol C7H6O3)/(138.12 g C7H6O3) * (1 mol C9H8O4)/(1 mol C7H6O3) *(180.157 g C9H8O4) = 2.6831 g C9H8O4 Actual Yield: 2.509 g C9H8O4 Percent Yield of Aspirin = Actual Yield/Theoretical Yield * 100% = 2.509 g / 2.6831 g = 93.51%

If you assume that there are some of both of the starting materials left unreacted (assuming the reaction won't go to 100% completion), at the end of the reaction, what happens to each of them? (Hint: what happens to the reaction when you add water? How soluble are the reactants?)

If there are some of the acetic anhydride and salicylic acid left at the end of the reaction, it is possible to remove one of the reactants but not the other. For example, by adding water, we can rinse away acetic anhydride because it is soluble in water. But salicylic acid is not soluble in water so it is difficult to remove it.

To make a new stock, you take 2mL of the solution above, place it into a 25mL volumetric flask, and dilute to volume with iron(III) nitrate. What is the concentration of this solution? What color is the solution in the flask?

M1V1 = M2V2 (0.005792 M)(0.002L) = (0.025L)(M) M = 0.0004634 = 4.634 * 10-4 M This solution would be purple.

How to quantitatively transfer a solution?

Note: To quantitatively transfer a solution, place deionized water into your squirt bottle and use it to rinse the original beaker with a small amount (~1-2 mL) of distilled water. Transfer this rinse water to the volumetric flask. Repeat 2-3 times making sure all solids are transferred being careful to not exceed the total volume of the flask (25 mL in this case).

Think about possible impurities present in your product. Discuss with those around you and list at least 2.

Possible impurities in our product could be starting material/reactants (such as acetic anhydride or salicylic acid), byproducts, or solvent.

Calculation of Percent Purity for Aspirin Standard Curve of Salicylic Acid Equation: Absorbance = 1781.2(Concentration) - 0.0202 iron 3 nitrate last solution was 0.025 L 1 mL of aspirin solution 138.12 g/mol for SA 0.1070 g aspirin weighed

Standard Curve of Salicylic Acid Equation: Absorbance = 1781.2(Concentration) - 0.0202 If we plug in the absorbance value of our aspirin sample at the end: Concentration of Solution 2 = 0.00009892 Concentration of Solution 2 = moles of salicylic acid / 0.025 L solution So in solution 2, there were 0.0000024731 moles of salicylic acid. To calculate the moles in solution 1, we can divide moles of salicylic acid in solution 2 by 0.001 L to find the concentration of solution 1. So the concentration of salicylic acid in solution 1 is 0.0024731. We can find the moles of this solution by multiplying by 0.025 L. So the moles of salicylic acid in solution 1 is 0.00006183. 0.00006183 moles of salicylic acid * (138.12 g salicylic acid)/(1 mol salicylic acid) = 0.008540 g salicylic acid To find the percent purity, we can use the amount of solid aspirin we weighed in the beginning to find our absorbance of the final aspirin table (see Table 5) 0.008540 g salicylic acid / 0.1070 g solid aspirin sample * 100% = 7.981% of salicylic acid in the aspirin sample 100% - 7.981% = 92.02 aspirin in the aspirin sample So our percent purity is 92.02%

Lab Tips

The darker purple the solution, the more salicylic acid impurities are present. Absorbance should always be <1.0 Standard curve range should have absorbance 0.1 - 1.0 Spectrophotometer will be calibrated with unreacted Fe(NO3)3 Data for the standard curve must be taken at the same wavelength for all concentrations

Aspirin Sample ANalysis Procedure General

The whole point is that not all salicylic acid was used in reaction, if we complex our aspirin with iron 3 nitrate, we can analyze sample to figure out how much salicylic acid is in the synthesized aspirin. 1. Combine 0.010 grams of our aspirin, add 5 mL of ethanol, 10 mL of DI water. 2. Transfer this solution to 25 mL flask. Add DI water to mark. 3. Transfer this solution to 50 mL beaker. Get 1 mL of this solution to 25 mL flask. Add iron 3 nitrate to mark. 4. Record absorbance and determine % purity.

Appropriate Glassware for Dilution

Volumetric pipettes, graduated pipettes, and volumetric flasks are among the best choices. Graduated cylinders can be used, but are considerably less accurate than volumetric glassware.

What are two things that we would want to know about a product to determine the success of a synthesis?

We would want to know the actual yield and the theoretical yield, in order to find percent yield. We would want to know about the percent purity (look at unreacted starting materials, by products, and solvent). Compare the amount of starting materials to ending materials. We would not color changes, light emissions, and possibly heat release.

Filtering

You will be using a Buchner funnel for Aspirin Buchner funnels are best when the solid is desired Gravity filters are best when the liquid is of interest and there are solid impurities present. Use filter paper. Buchner Filtering Notes The open tip at the bottom of the funnel should be turned away from the side arm of the flask. The filter paper should be wet just prior to adding your sampl Use only minimal amounts of water (<5 mL) to rinse your sample. Turn off the vacuum before removing your product after filtering