# What happens when I use cyclohexanol to prepare cyclohexene?

I've done a student experiment using cyclohexanol to prepare cyclohexene.

We mix $10.5~\mathrm{g}$ cyclohexanol and $5~\mathrm{mL}$ $85\%$ $\ce{H3PO4}$ in a $50~\mathrm{mL}$ flask, then distill while heating.

I want to know during this process what kind of side reaction happens because I notice there is something light yellow in the flask. After reaction, the liquid remaining in the flask is red and upon it there is something dark green and muddy.

I have a guess that there is some phenol in the cyclohexanol (since cyclohexanol may be prepared from phenol), and that during reaction the phenol oxidized, producing 1,2-benzoquinone (which is red) and 1,4-benzoquinone (which is yellow). Is this idea reasonable? If it is, why does the red color appear later?

And about the dark green thing: can it be produced by some kind of carbonized organic matter? I have been told that if the $\ce{H3PO4}$ and cyclohexanol were not well mixed, there would be some cyclohexanol carbonization.

(Can I ask one more question?) We are required to compare the chemical properties of cyclohexene and cyclohexane. So we reacted them with $\ce{Br2}/\ce{CCl4}$ respectively, under light or covered by aluminium foil. Should it be different when cyclohexene reacts under light or covered by aluminium foil? I notice the result is slightly different; the reactions in the light become a little opaque.

• Hmm, it's strange - have done everything right? – Mithoron May 7 '15 at 15:12
• @Mithoron I don't know... but other classmates also get something like this. However, most of them only get something light yellow. Only some get red. I know our reagent may not be that pure - they want to save cost. – Asydot May 7 '15 at 15:29
• Light yellow should be ok - cyclohexene - it's not purified so it's slightly colored. Othrwise you probably did sth wrong. – Mithoron May 7 '15 at 15:40