With Hydrocarbons
The boiling point of the homologous series increases gradually as they go in an increasing direction (Alkanes, Alkenes, Alkines, Aren…) because the molecular mass also increases at that time.
Example: C2H6 > CH4
As for isomers, those with higher boiling points have longer chains
With derivatives
R-X derivative, boiling point will increase as X attracts electrons more strongly if there is no hydrogen bond
Example: C4H9
The halogen derivative of the alkene boils and melts at a lower temperature than the derivative of the corresponding alkane.
Derivatives of Benzene: Putting a simple substituent on the benzene ring will raise the boiling point.
With compounds containing functional groups
When two substances have the same homologous series, the one with the larger molecular mass has the higher boiling point
For example: CH3OH and C2H5OH, C2H5OH has a higher boiling point
For compounds with different functional groups, the boiling points of organic substances are different
The boiling points of alcohols, aldehydes, acids, ketones, and esters are respectively in the following order:
Acids > Alcohols > Amines > Andehites, Ketones and Esters
Ketones > Andehite
The electron-absorbing radicals (Phenyl, Chlorine …) will reduce the boiling point because the H-bond will become less stable
For example: Cl-CH2COOH Cl > Br > I