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.
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!