The structure of 2-Methyl-5-(1,2-dimethylpropyl)nonane can be written as follows:
CH3-CH(CH3)-CH2-CH(CH3)-CH2-CH2-CH2-CH2-CH3
This compound consists of a nonane backbone with a methyl group attached to the second carbon and a 1,2-dimethylpropyl group attached to the fifth carbon.