(N/A) Methoxymethane $(CH_3-O-CH_3)$ and ethanol $(C_2H_5OH)$ are isomers with the same molecular formula $C_2H_6O$ and the same molar mass of $46 \ g \ mol^{-1}$. Despite this,their boiling points are different.
In methoxymethane,there is an ether group,and there is no polar $O-H$ bond. Therefore,there is no intermolecular hydrogen bonding in ethers.
In ethanol,the $O-H$ bond is polar,and there is intermolecular hydrogen bonding between different ethanol molecules. Let $C_2H_5 = R$,then the intermolecular $H$-bonding is as shown in the figure.
Due to these intermolecular hydrogen bonding forces,ethanol has a higher boiling point compared to methoxymethane.