Nomenclature and Structure of Carbonyl Group

Aldehydes and ketones are both carbonyl compounds — every molecule in either family carries a carbon-oxygen double bond, $\text{C=O}$, as its characteristic functional group. In an aldehyde the carbonyl carbon carries at least one hydrogen atom, written as the group $-\text{CHO}$; in a ketone the carbonyl carbon is flanked on both sides by carbon-containing (alkyl or aryl) groups, written generally as $\text{R-CO-R}'$.

Because they share this one functional group, aldehydes and ketones are conveniently treated together — the same naming rules and much of the same structural reasoning about the $\text{C=O}$ bond apply to both. This section builds the two pieces needed before any reaction chemistry can be discussed:

What this section covers

• Nomenclature — how an individual aldehyde or ketone is named, both by its older common name and by the systematic IUPAC name.
• Structure of the carbonyl group — the hybridisation, geometry, and bond polarity of the $\text{C=O}$ unit that governs how aldehydes and ketones behave chemically. …