What is wrong with the names 2-ethyl-4 and 4-dimethylpentane?

The names "2-ethyl-4" and "4-dimethylpentane" are incomplete and incorrect. There are a few issues with these names:

1. Lack of main functional group: Organic compounds often have a main functional group, such as an alcohol, aldehyde, or ketone, which determines the class to which they belong. However, both of these names do not mention any functional group.

2. Incomplete numbering: In organic chemistry, it is necessary to assign specific numbers to carbon atoms in a molecule to indicate the position of substituents. In both names, no numbering is provided beyond the substituent groups.

To correct these names, it is crucial to determine the full structure of the compound and then assign numbers to the carbon atoms. Once the complete structure and numbering are established, appropriate prefixes like "2-ethyl" and "4-dimethyl" can be used to indicate the substituent groups attached to specific carbon atoms. Additionally, the main functional group should be identified and named accordingly.

For a more accurate answer, it would be helpful to have the complete structure of the compound in question.

I don't know what 2-ethyl-4 is.

The 4-dimethylpentane doesn't tell you where the two methyl groups are located.If both are on 4, then it would be 4,4-dimethylpentane.