Video Transcript
Toluene can undergo the following reaction to produce a disubstituted derivative. What name does this product have? (A) Para-nitrotoluene, (B) meta-nitrotoluene, (C) anti-nitrotoluene, (D) syn-nitrotoluene, or (E) ortho-nitrotoluene.
Toluene is a monosubstituted benzene derivative in which a methyl group is bonded to a benzene ring. So this compound is also called methylbenzene. When toluene is treated with nitric acid in the presence of a sulfuric acid catalyst, a nitration reaction occurs and a nitro group is added to the benzene ring adjacent to the methyl group. We need to determine the name of this disubstituted derivative. There are a number of ways to name this disubstituted benzene derivative. One way to name this compound is to number the carbon atoms of the benzene ring so that the substituents have the lowest possible position numbers. We then list the position numbers and substituents followed by the name benzene. So this compound is 1-methyl-2-nitrobenzene.
We could also identify this compound as a toluene derivative which has a nitro group attached to the second carbon atom of the ring. So we could also name the compound 2-nitrotoluene. But neither of these names match the names provided in the answer choices. So let’s look at another way to name disubstituted benzene derivatives. When the two substituents are attached to carbon atoms one and two of the benzene ring, we can use the prefix ortho- or o- to describe the relative position of the two substituents. When the substituents are attached to carbon atoms one and three, we use the prefix meta- or m-. And when the two substituents are attached to carbon atoms one and four on opposite sides of the benzene ring, we use the prefix para- or p-.
As the methyl and nitro groups are bonded to carbon atoms one and two of the benzene ring, we can use the prefix ortho- or o-. Using this prefix, we could call this compound ortho-methylnitrobenzene or o-methylnitrobenzene. Both of these names indicate that the compound contains a benzene ring structure that has a methyl substituent and a nitro substituent bonded to adjacent positions. We can also name this compound as a derivative of toluene using the ortho- prefix. As toluene is composed of a methyl group attached to a benzene ring, we simply need to name the substituent nitro and the name, giving us ortho-nitrotoluene and o-nitrotoluene.
Looking at the answer choices, we can see that answer choice (E) matches one of the six possible names we have given for this compound. So this disubstituted derivative shown produced from the nitration of toluene is called ortho-nitrotoluene, answer choice (E).
