Answer
Using the molecular formula $C_{2}H_{6}O$ you can draw the alcohol ethanol and dimethyl ether (see picture). They differ in that ethanol contains the functional group OH whereas dimethyl ether consists of the functional group ether, i.e. an oxygen sandwiched between two carbon atoms. What’s more, both have a dipole moment. However, due to the hydrogen bonding in ethanol the boiling point increases. So ethanol has a higher boiling point than dimethyl ether. The hydrogen bonding in ethanol also accounts for other properties with regards to alcohol, i.e. both hydrophilic and hydrophobic which makes ethanol highly miscible with water.
Work Step by Step
- You can use a lewis structure to draw both substances:
(1) Determine the central atom, usually the least electronegative atom. Keep in mind, that hydrogen is never the central atom. So use carbon for ethanol. As the other substance has to differ from the first one, the only thing you can do is to use oxygen as the central atom (just like water) for dimethyl ether.
(2) Usually, carbon atoms consist of four bonds while the oxygen atoms feels lucky with two or three bonds.
(3) Take care of the octet rule, i.e. the sum of the bonds + lone pairs must not exceed four.
- To find out some differences you can start by drawing the dipole moment for each substance (see picture). A high dipole moment as in ethanol leads to a higher boiling point. Additionally, you can look at the functional groups to see if they differ. For example, the hydrogen bonding in an OH-group causes an alcohol to become both hydrophilic and hydrophobic.
