Answer : The structure are shown below and the number of stereoisomers are possible in 3,5-dimethylnonane and 3,7-dimethyle-5-ethyldecane are 4 and 8 respectively.
Explanation :
Chiral carbon : It is carbon which is attached to the different types of atoms or molecules.
The number of stereoisomers possible for a compound is related to the number of chiral centers (n) present in it as,
![\text{Number of stereoisomers}=2^n](https://tex.z-dn.net/?f=%5Ctext%7BNumber%20of%20stereoisomers%7D%3D2%5En)
where,
'n' is the number of chiral carbon present in the compound.
The number of chiral carbon present in 3,5-dimethylnonane is, 2 that means n = 2 (carbon-3 and carbon-5)
![\text{Number of stereoisomers}=2^n=2^2=4](https://tex.z-dn.net/?f=%5Ctext%7BNumber%20of%20stereoisomers%7D%3D2%5En%3D2%5E2%3D4)
The number of stereoisomers are possible in 3,5-dimethylnonane is, 4
The number of chiral carbon present in 3,7-dimethyle-5-ethyldecane is, 3 that means n = 3 (carbon-3, carbon-5 and carbon-7)
![\text{Number of stereoisomers}=2^n=2^3=8](https://tex.z-dn.net/?f=%5Ctext%7BNumber%20of%20stereoisomers%7D%3D2%5En%3D2%5E3%3D8)
The number of stereoisomers are possible in 3,7-dimethyle-5-ethyldecane is, 8