The reason your classmate cannot find the compound in a chemical reference manual is that 2,4-diethyl-4-ethoxyhexane is the incorrect name for the compound. What is the correct name

3-ethoxy-3-ethyl-5-methylheptane

Explanation:

In this case, we have to identify the longest chain of carbon in this case the longest chain is made with 7 carbons. Then we have to assign carbon 1. In this case, carbon 1 is the one nearest to the ethoxy group. With this in mind, we will have a methyl on carbon 5, a methyl on carbon 3 and an ethoxy group in carbon 3, so the name would be 3-ethoxy-3-ethyl-5-methylheptane.

See figure 1

I hope it helps!