Name the structure ch3 ch2 ch ch ch2 ch3 ch3 ch ch2 ch3 ch3 using the iupac system. 1. 2,3-diethyl-4-methylhexane 2. 3-butyl-4-methyl-hexane 3. 4-ethyl-3,5-dimethylheptane 4. 3,5-dimethyl-4-ethylheptane

This, CH3 CH2 CH CH CH2 CH3 CH3 CH CH2 CH3 CH3, is not a proper structure.

I am going to restructure it the best it can be done from the information given.

CH3 CH2
         |
CH3 CH CH CH2 CH3
               |
      CH3 CH CH2 CH3

Now I am going to draw only the C of the main chain and place the  numbers to count the number of Cs in tha chain


 (1)  (2) 
  C  - C -
         |
   (3) C - C(4) -
               |
             - C - C - C -
             (5)   (6)  (7)  


Seven Cs => the compound is a heptane.

No you can see that there are three substitutes: one methyl group at the C number (3), one ethyl group at C number 4, and  one methyl group at the C number 5.

With that information, the product is named

4 - ethyl - 3, 5 dimethylheptane (which is the option number 3 of the list).

The ehtyl group is named before the methyl group to respect the alphabetical order, as per IUPAC rules.