Having trouble naming hydrocarbons with the IUPAC nomenclature rules
The first name has the correct alphabetical order of groups: ethyl before dimethyl. The &quot;d&quot; of dimethyl is not involved in alphabetizing. The numbering is correct because the one-to-one comparisons of locants is {1,2,4 &lt; 1,3,4}. The correct name is 4-ethyl-1,2-dimethylcyclohexane. For a brief set of IUPAC rules applicable to this question see, https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/nomen1.htm