What is the structural formula of 2-methylbutan-2-ol (sometimes called 2-methyl-2-butanol)?

            CH3
             |
  CH3 - C - CH2 - CH3
             |
            OH

Explanation:

1) given name: 2-methylbutan-2-ol

2) that means:

- the main chain is a butane (4 carbon atoms): CH3 - CH2 - CH2 - CH3

- 2 methyl => there is a methyl group in the second carbon =>

            CH3
             |
  CH3 - CH - CH2 - CH3

- 2 - ol => there is a hydroxil (OH) group in the second carbon =>

            CH3
             |
  CH3 - C - CH2 - CH3
             |
            OH

And that is the structure of the compound.