# Decrease in Aspirin Melting Point

• Puchinita5
In summary, a student performed an experiment using a water bath of 90 degrees C instead of 50 degrees C and the final product was tested for phenols with ferric chloride, resulting in a negative test. However, the melting point of the dry product was lower than expected at 122-125 degrees C. This could be due to a greater temperature causing the reaction to shift to the right, resulting in a more pure product. Additionally, the higher heat may have caused the formation of an impurity that is lowering the melting point. Further analysis is needed to determine the exact cause of the lower melting point.
Puchinita5

## Homework Statement

A student performed the reaction in this experiment using a water bath of 90 degrees C instead of 50 degrees C. The final product was tested for the presence of phenols with ferric chloride. This test was negative (no color observed); however, the melting point of the dry product was 122-125 degrees C. Explain these results as completely as possible.

## Homework Equations

Salicylic Acid + Acetic Anhydride -------> Acetyl Salicylic Acid (Aspirin) + Acetic Acid
Melting point of aspirin should be 134 degrees C.

## The Attempt at a Solution

Ummm. I have no idea. I would assume the greater temperature would cause the reaction to shift to the right, making more of a pure product and hence the negative ferric chloride test. But I'm not sure how this would lower this melting point?

If I'm going to take a wild, WILD guess, perhaps the greater heat is also causing another product to form, which is making the aspirin less pure but this other product doesn't show up in a phenol test? And maybe this extra product is lowering the melting point somehow?But since this "other product" isn't alluded to in the reaction, I feel like I am making it up.

Thank you for your help!

It's some impurity that's causing the product to melt at a lower temperature. As for what it is, if the product wasn't recrystallized, it might be the solvent; it might be some side product. Dunno, but it's definitely an impurity.

## 1. What causes a decrease in the melting point of aspirin?

A decrease in the melting point of aspirin is typically caused by impurities in the substance. These impurities can disrupt the crystal structure of the aspirin, making it easier for the molecules to break apart and melt at a lower temperature.

## 2. Can changes in atmospheric pressure affect the melting point of aspirin?

Yes, changes in atmospheric pressure can affect the melting point of aspirin. The higher the atmospheric pressure, the higher the melting point of aspirin will be. This is because the pressure helps to hold the molecules together, making it more difficult for them to break apart and melt.

## 3. Are there any other factors besides impurities that can cause a decrease in aspirin's melting point?

Yes, there are other factors that can contribute to a decrease in aspirin's melting point. These include changes in temperature, exposure to light or moisture, and the presence of other chemicals that may react with the aspirin molecules.

## 4. How can a decrease in aspirin's melting point affect its effectiveness?

A decrease in aspirin's melting point can affect its effectiveness by altering the dosage and absorption of the medication. If the melting point is lower, the aspirin may dissolve more easily, making it more quickly available for absorption in the body. This could lead to a higher dosage being absorbed and potentially causing adverse effects.

## 5. Is there a way to prevent a decrease in aspirin's melting point?

Yes, there are ways to prevent a decrease in aspirin's melting point. The most effective method is to ensure that the aspirin is stored properly, in a cool and dry place. This will help to prevent exposure to moisture and other substances that could affect its melting point. Additionally, using high-quality, pure aspirin can also help to prevent impurities that can cause a decrease in melting point.

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