Britannica
Sources used in this answer
Which aldehydes are gases or liquids under ordinary conditions?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
aldehyde
Alcohols may be oxidized to give aldehydes, ketones, and carboxylic acids. The oxidation of organic compounds generally increases the number of bonds from carbon to oxygen, and it may decrease the number of bonds to hydrogen.
Under ordinary conditions, the physical state of an aldehyde is primarily determined by its molecular weight.
- Gases: Formaldehyde (HCHO), the simplest aldehyde, exists as a gas under standard conditions.1
- Liquids: Acetaldehyde (CH₃CHO) boils at approximately room temperature. Most other aldehydes are liquids under ordinary conditions, provided they do not have a high molecular weight.1
The polarity of the carbonyl group results in higher boiling points for aldehydes compared to nonpolar hydrocarbons of similar molecular weight, as the polar molecules require more energy to separate.1