Here you will find material for Experiment 21 - Synthesis of Aspirin. This includes detailed guides for the pre-lab, data sheet, post-lab, and quiz questions. Experiment 10 will have you synthesize two esters of salicylic acid. Remember, the lab may change or be modified from semester to semester!

Experiment 21 is broken up into three main parts - A. Synthesis of Aspirin, B. Synthesis of Methyl Salicylate, and C. Analysis of Aspirin.

A. Synthesis of Aspirin

This part will have you synthesize aspirin from salicylic acid. You will synthesis aspirin with salicylic acid being your limiting reagent. That means the amount of salicylic acid you use will determine how much aspirin you will make. This synthesis will then be used to analyze the purity and percent yield in part C. The synthesis of aspirin may take a significant amount of time since you will need to let it dry in order to get a reasonable yield. It is recommended you complete this part first to give it the most time to dry.

B. Synthesis of Methyl Salicylate

This part will have you synthesize methyl salicylate from salicylic acid. You will then use correct technique to note the odor.

c. analysis of aspirin

This part will have you analyze your synthesis of aspirin from part A. Using one three test tubes, you will mix combine ethanol and Iron(III) chloride to each. You will then add salicylic acid to one and your synthesized from Part A in another test tube. The third test tube will be your control. You will then note your observations.

CALCULATOR (LINK)

A scientific calculator is needed for calculations on quizzes. Some labs have calculations that need to be turned in before leaving.

LAB GOGGLES (LINK)

Required eye protection. Must be worn at the start of the experiment and until leaving

COMBINATION LOCK (LINK)

A combination lock is required to lock your equipment drawer for the semester.

bottlenecks

This experiment can be completed relatively quickly. The only potential bottleneck will be Part A (synthesizing aspirin). This is because significant amount of time is required for the sample to dry and yield reasonable results.

Split Tasks

Part B. (synthesis of methyl salicylate) can be done quickly by having one lab member complete the procedure while others complete part A. The odor of the sample can then be noted by all lab members. Part C is dependent on how fast you can complete part A since it requires the sample yielded to analyze.

reactions

Pay attention to the synthesis reactions in this experiment. These will be needed to determine the expected number of moles of aspirin (1:1) which will be used in your percent yield calculations. The synthesis reactions may also appear on your quizzes.

converting to moles

Understanding how to convert to moles will be essential. For this experiment, you will synthesize aspirin from salicylic acid. The amount of salicylic acid used will be the limiting reagent and dictate how much aspirin will be synthesized. Using the recorded amount of salicyclic acid used, you can find the expected amount of aspirin. This expected value will be compared to the amount obtain from your experiment to calculate percent yield.

Number of moles = mass of substance ÷ molar mass of substance

calculating percent yield

This lab will require you to calculate the percent yield of the aspirin synthesis. Percent yield is calculated by dividing your actual yield (mass of aspirin you made) with the expected or theoretical yield (mass you calculated) multiplied by 100.

Percent Yield = (Actual Yield ÷ Theoretical Yield) x 100

A percent yield that is less than 100 means that you made less than what you were supposed to get. This could be a number of reasons such as loss of substance during transfer.

A percent yield that is more than 100 means that you have more than what you were supposed to get. This could be a number of reasons such as impurities or that the sample was not completely dry.