Hi, I have a question on how to distinguish cyclohexane from benzene through lab tests i.e. chemical reactions (except for burning and observing the amount of soot produced, because it is not a very conclusive test)
So far the only thing I could think of is adding halogens to both of them. Since alkanes would undergo free radical substitution only in the presence of UV light or high temperature, whereas benzene would require the presence of a catalyst at room temperature. But I don't see how this would help tell them apart. Is there any decolonization involved for benzene or cyclohexane?
I've read through all my lecture notes, tried looking for videos on benzene reactions but because it's toxic there isn't any videos of help I could find. There also isn't much information on the net, which is exactly why i'm seeking help here. So I'd really appreciate if i wasn't just dumped with links. Thanks!
To distinguish between cyclohexane and benzene through lab tests, there are a few different chemical reactions and tests you can perform. Here are two common methods:
1. Reaction with bromine water:
Cyclohexane does not react readily with bromine water at room temperature or in the dark. However, benzene reacts with bromine water in the absence of UV light or heat, and the reddish-brown color of bromine water disappears as benzene undergoes electrophilic substitution. So, you can add bromine water to both cyclohexane and benzene and observe if there is a decolorization reaction. If there is a reaction and the color disappears, it indicates the presence of benzene.
2. Reaction with potassium permanganate:
Cyclohexane does not react with potassium permanganate (KMnO4) under normal conditions, whereas benzene undergoes oxidative cleavage with KMnO4 to produce carbon dioxide and a brown precipitate of manganese dioxide (MnO2). By adding KMnO4 to the compounds and observing any color change or precipitate formation, you can distinguish between cyclohexane and benzene.
It is important to note that these tests are not absolute proof but can provide indications based on characteristic reactions. Also, always ensure appropriate safety precautions when working with chemicals in the lab.
Additionally, it's worth mentioning that while benzene is indeed toxic, proper lab techniques and safety measures can mitigate any potential risks. If you are unsure or uncomfortable performing these tests yourself, it is best to consult your instructor or a qualified professional for guidance and assistance in the lab.