Difference between alcohols

Question

Hi!

I have done a lab where I test the solubility of a few alcohols with water, and what happens when I ignite them. The alcohols I have used are, and the results I got are:

1. Methanol: Easy to ignite, blue flame. Very soluble in water.
2. ethanol: Easy to ignite, blue flame. Very soluble in water.
3. 1-propanol: Possible to ignite, yellow flame. Soluble in water
4. 1-butanol: Pretty hard to ignite, but there is a yellow flame. Pretty bad solubility in water
5. 1-pentanol: Unable to ignite until I dip a paper in it and then ignite the paper. Yellow flame. Very bad solubility in water
6. Ethylene glycol: Used paper to ignite here as well. Yellow flame. Very soluble in water
7. Glycerol: Unable to ignite. Very soluble in water
8. Unknown isomer of one of the first five alcohols: Pretty easy to ignite and I see a yellow flame. It is soluble in water.

From the information I know in the above, I need to figure out what the unknown isomer is. It turned out to be 2-propanol (Isopropyl alcohol). But I do not know how to figure it out from the information I have above. I would be very thankful for help!

Thanks!

Answer 1

Based on the yellow flame, ease of ignition and solubility (actually miscibility) in water, that would be a pretty good guess, but you could not definitely identify it as isopropyl alcohol. You'd need additional tests such as maybe density, boiling point, etc.

Side note: when we speak of two liquids mixing with each other, we use the term "miscible" instead of soluble. So, we say that ethanol is miscible with water.