[Chemistry] Effects of iron (III), and iodine on esters

[Sean1218]

More specifically, on acetylsalicylic acid (both crude/made in class, and commercial/store-bought), and salicylic acid. Please hang with me, I'll get to my question in a second.

I did these tests:

Crude aspirin w/ iron (III): Translucent, light peach in colour
Crude aspirin w/ iodine: Cloudy, orange in colour

Commercial aspirin w/ iron (III): Cloudy, violet in colour; no change after adding a few drops of NaOH
Commercial aspirin w/ iodine: Opaque, dark, olive green in colour [this one should be dark purpley, so something went wrong]

Salicylic acid w/ iron (III): Opaque, dark purple in colour

Basically, I have to determine why I got the results I did (i.e. colour changes). Mainly why the commercial aspirin w/ iodine turned olive green, but crude aspirin was orange (since they contain starch it should be dark purpley, so what could have happened?), and why the salicylic acid w/ iron (III) turned dark purple.

Explanations for the crude/commercial aspirin with iron, and why adding NaOH didn't have any effect with the commercial would also be helpful if you know, but I mainly just need the other ones.

I did a bit of research for other tests that I ran (not listed) and managed to answer those, but these are the ones that I haven't been able to find much on.

So, any help would be great!

 

[Borek]

One thing that immediately jumps to mind is that commercial aspirin may contain many things, depending on brand - are you sure it is just starch that is added? Perhaps what you had was aspirin with ascorbic acid?

 

[Sean1218]

Well, I don't know starch was added, but my teacher said it should be dark purple, so I assumed.

 

[Sean1218]

Ok, I managed to answer most of them. All except for the iodine tests. I have no idea why it turned out the way it did. Anyone care to explain?

 

[DeeNos]

I would first like to commend you for conducting these experiments and taking the time to analyze and understand your results. It is important to note that the color changes you observed in your experiments are a result of the chemical reactions taking place between the compounds being tested.

Iron (III) is a strong oxidizing agent, meaning it can cause other substances to lose electrons and undergo a color change. In the case of crude aspirin, the light peach color is likely due to the presence of impurities in the sample. These impurities can react with the iron (III) to produce a lighter color, as seen in your experiment.

On the other hand, the commercial aspirin likely contains more pure acetylsalicylic acid, which would result in a darker color change when reacting with iron (III). The olive green color you observed could be due to the presence of other compounds in the commercial aspirin that are reacting with the iron (III) to produce this color. It is also possible that the concentration of iron (III) used in your experiment was not strong enough to produce the dark purple color expected.

In the case of salicylic acid, the dark purple color is most likely due to the formation of a complex between the iron (III) and the salicylic acid. This complex would have a different color compared to the pure salicylic acid.

As for the lack of color change when adding NaOH to the commercial aspirin with iron (III), it is possible that the NaOH was not strong enough to overcome the color produced by the reaction between the iron (III) and the aspirin. It could also be due to the presence of other compounds in the commercial aspirin that are interfering with the reaction.

Overall, it is important to keep in mind that the exact color changes observed in your experiments may vary depending on the purity of the compounds being tested, the concentration of the reagents used, and any impurities present. Further research and experimentation may be needed to fully understand the specific reactions and color changes observed in your experiments.