How do you define the system so that the energy changes are all transformations internal to an isolated system

What is the empirical formula of c6h18o3? ch3o c2h5o c2h6o c2h5o5

Sodium nitrite (nano2) reacted with 2−iodooctane to give a mixture of two constitutionally isomeric compounds of molecular formula c8h17no2 in a combined yield of 88%. draw reasonable structures for these two isomers. click the "draw structure" button to launch the drawing utility. place the two compounds in the appropriate boxes below.

Draw the structure for 5-isopropyl-2-methyl-3-nonene