In organic chemistry, what does oxidation refer to?

In organic chemistry, oxidation is defined as the loss of electrons or an increase in oxidation state. This concept plays a crucial role in understanding various chemical reactions, particularly redox reactions, where the transfer of electrons occurs. When a molecule is oxidized, it typically loses hydrogen or gains oxygen, leading to an increase in its oxidation state.

For instance, consider the oxidation of an alcohol to a ketone or aldehyde. During this process, the alcohol loses electrons, and its oxidation state increases due to the introduction of a higher number of oxygen atoms in the molecular structure compared to the original alcohol. This principle allows chemists to predict the behavior of organic compounds during various reactions.

The other options provide definitions that do not align with the established understanding of oxidation in organic chemistry. The gain of electrons describes reduction rather than oxidation, and the increase in the size of molecules or the addition of carbon does not necessarily indicate an oxidation process. Thus, the correct answer accurately captures the essence of what oxidation entails in this field of study.