Ethylene glycol (HOCH2CH2OH), the major substance in antifreeze, has a normal boiling point of 198 °C. By comparison, ethyl alcohol (CH3CH2OH) boils at 78 °C at atmospheric pressure. Ethylene glycol dimethyl ether (CH3OCH2CH2OCH3) has a normal boiling point of 83 °C, and ethyl methyl ether (CH3CH2OCH3) has a nomral boiling point of 11 °C. (a) Explain why replacement of a hydrogen on the oxygen by a CH3 group generally results in a lower boiling point.

Video transcript

Hey everyone, we're told that methanol has a boiling point of 64 degrees Celsius, while methyl amine has a boiling point of negative six degrees Celsius. Which of the following explains why replacing the oxygen with a nitrogen lowers the boiling point. Now, thinking about what affects our boiling point, we know that our inter molecular forces will affect this and when we compare our two compounds, we know that they both have hydrogen bonding present. So how So one of these has weaker hydrogen bonding than the other, and we know that it's going to be nitrogen because it has a lower electro negativity than oxygen and a lower electro negativity leads to weaker hydrogen bonding. And this is the reason why replacing oxygen with a nitrogen lowers the boiling point. So I hope that made sense. And let us know if you have any questions.