You have a bottle of cyclohexane and a bottle of cyclohexene, but they are unlabelled. Which of the following reagents would be the best choice to use to distinguish which was which?
a. KOH/H2O
b. KOH/CH3OH
c. CH3ONa/CH3OH
d. CH3CH2ONa/CH3CH2OH
e. (CH3)3COK/(CH3)3COH
My textbook isn't helping. Thank you.
To determine whether the unlabelled bottle contains cyclohexane or cyclohexene, we can exploit their different reactivity towards certain reagents. In this case, we are looking for a reagent that can distinguish between them based on their reaction.
Cyclohexane is an alkane, while cyclohexene is an alkene. The key difference between these two compounds is the presence of a carbon-carbon double bond in cyclohexene.
One of the most common reactions that differentiate alkanes and alkenes is their reaction with a strong base such as potassium hydroxide (KOH). Alkanes are generally unreactive towards bases, but alkenes can undergo an elimination reaction, known as a dehydrohalogenation.
Based on this information, the best choice out of the given reagents would be (b) KOH/CH3OH. This reagent mixture contains a strong base, KOH, and methanol (CH3OH) acts as a solvent.
The reaction between the alkene (cyclohexene) and the strong base KOH/CH3OH would result in the elimination of a hydrogen atom from one of the carbons adjacent to the double bond, resulting in the formation of a double bond. However, the alkane (cyclohexane) would not undergo any reaction with this reagent.
Therefore, if the reagent (b) KOH/CH3OH is used and a reaction occurs, it would indicate the presence of cyclohexene, whereas a lack of reaction would suggest the presence of cyclohexane.
It's important to note that this is a simplified explanation, and further analysis, such as spectroscopic techniques, would be needed to confirm the identity of the compounds with certainty.