Question

check the box under each molecule in the table below that is an isomer of this molecule: if there are no isomers, check the none of the above box under the table.

Explanation:

Step1: Determine the molecular formula of the given molecule

The given molecule is 1,4 - dioxane with the molecular formula $C_4H_8O_2$.

Step2: Analyze the first option

The first molecule has a double - bond and two hydroxyl groups. Its molecular formula is $C_4H_8O_2$. It is an isomer.

Step3: Analyze the second option

The second molecule is 1,3 - propanediol with the molecular formula $C_3H_8O_2$. It is not an isomer.

Step4: Analyze the third option

The third molecule is methyl acetate with the molecular formula $C_3H_6O_2$. It is not an isomer.

Step5: Analyze the fourth option

The fourth molecule is propanoic acid with the molecular formula $C_3H_6O_2$. It is not an isomer.

Answer:

Check the box under the first molecule (the one with a double - bond and two hydroxyl groups).