Assume that you have two unlabeled bottles, one with cyclohexane and one with cyclohexene. How could you tell them apart by carrying out chemical reactions?

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Hi, everyone. Let's look at our next question. A student needs to determine if one of the two unlabeled bottles contains phenol. How can he confirm this with a chemical reaction? A mix each sample with a few drops of sodium hydroxide and look for the formation of bubbles. B add a few drops of aqueous ferric chloride to each sample and look for a violet or purple color change c heat each sample with concentrated sulfuric acid and observe the release of carbon dioxide gas or D mix each sample with ethanol and observe for dec colorization. We can often use various reagents to test mystery solutions because they react in expected ways with different chemicals. So what is a test for phenol? Well, that would be choice B the addition of aqueous ferric chloride. This is because phenol, unlike most alcohols is a pretty good acid. Normally, alcohols won't lose that hydrogen, but in a case of phenol. So I've drawn my benzene ring with my oh group, the de localization of the electrons in the benzene ring stabilizes the negative charge on the oxygen when it loses that hydrogen. So if you take phenol, which is colorless and you add aqueous ferric chloride. So fecl three, it can react and form a complex. So the folate ion that forms forms a complex with the iron ion. So you'll get this complex of fe three plus which are iron cion with six phenol ions. So that would be my benzene ring with an O minus on it. And six of those form that complex and many transposition metal complexes have very intense colors. And in this case, this forms a violet or purple color. And then of course, it will also produce hydrochloric acid balance. This six of our phenols and six hydrochloric acid aqueous. But again, the key product here is that complex of phenol ions with an iron ion which has this purple color. So you go from a colorless solution to a purple solution by adding that ferric chloride. And that will tell you that you have phenol present. When we look at our other answer. Choices. Choice, a adding sodium hydroxide and looking for bubbles. Well, you would see this reaction if you add sodium hydroxide to plain old water, it will react rather violently with the water and produce hydrogen gas. So hydrogen gas will form bubbles but not a test for phenol. So not what we're looking for to c heat each sample with concentrated sulfuric acid. And look for Co2. Well, that is not a test for phenol sulfuric acid heating with sulfuric acid can be a way of generating alkins from alcohols uh to release carbon dioxide gas, reacting sulfuric acid with calcium carbonate will release carbon dioxide gas, but it's not a test for phenol. So not what we're looking for. And finally, choice D mix each sample with ethanol and observe for dec colorization. Well, ethanol is a general dec colorizing reagent and often used as such. But this is not a specific reaction and will not be a something that proves that your solution is phenol since it can react this way with different compounds. So that's why choice D isn't our correct answer. So once again, to determine which solution contains phenol, the chemical reaction that can do this is choice B add a few drops of aqueous ferric chloride to each sample and look for a violet or purple color change. See you in the next video.

Assume that you have two unlabeled bottles, one with cyclohexane and one with cyclohexene. How could you tell them apart by carrying out chemical reactions?

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Key Concepts

Cyclohexane vs. Cyclohexene

Electrophilic Addition Reactions

Oxidation Reactions