Why does CH3C(O)CH2CH3 have a higher boiling point than CH3OCH2CH2CH3? They both have D-D bonds and I thought since the ether is more linear it would have a higher boiling point.
Ketones have a MUCH higher dipole than ethers.
Depending on the class, ethers are often considered to have NO dipole. Mind you, in Chem 201, ethers are considered to have a weak dipole.
Assuming very similar molecular weights, the boiling points of
Carboxylic Acids > Alcohols > Ketones > Aldehydes > Esters > Ethers > Alkanes
Ketones have a stronger dipole than aldehydes (the C-H dipole on an aldehyde is insignificant).
Here are some actual values:
propanoic acid 141.2 °C
butanol 117.7 C
butanone 79.64 C
butanal 74.8 C
methyl ethanoate 57.1 C
diethyl ether 34.6 C
*1 less carbon was used in esters/carboxylic acids to account for the extra oxygen present. Hence all compounds above have similar molecular weight/number of electrons.
Stacking and hence a linear molecule is more important when you’re comparing the SAME functional group.