Question

Pinacol is
A) 3-methyl butan-2-ol
B) 2, 3-dimethyl butan-2, 3-diol
C) 2, 3-dimethyl-2-propane
D) None of the above

Answer 1

Hint:Pinacol is an organic compound that contains two hydroxyl groups. The carbon skeleton of pinacol contains four carbon atoms.

Complete step by step reaction:
Pinacol is an organic compound. It is a white organic compound used in many organic reactions.
Pinacol is a diol i.e. it contains two hydroxyl groups.
Let’s draw the structure of pinacol;

So from the structure we know that there are two hydroxyl groups and six carbon atoms in the structure.
In the question, it is asked to write the IUPAC name of the compound.
Pinacol is the common name of this compound.
So let’s write the IUPAC name. We know that there are two –OH groups and six carbon atoms in total.
Let’s see the carbon skeleton and the substituents attached.
-We always select the longest carbon chain as the carbon skeleton, here the straight chain containing the 4 carbon atoms is taken as the carbon skeleton.
Hence carbon skeleton is butane.
Then we take a look at the substituents, there are two methyl groups and two –OH groups as the substituents in the second and third carbon.
We know that we will give a prefix as methyl for $-C{{H}_{3}}$ group and a suffix –ol for the hydroxyl groups.
So now we can use the IUPAC name of pinacol as, 2, 3-dimethyl-2, 3-butanediol.

So the correct option is option (B).

Note: While writing the IUPAC name of the compound ,if the same substituents are present in two or more carbons, then the number of the same substituents should be specified as di, tri etc. We should name all the substituents, even if there are the same substituents present.