Both carboxylic acids and esters contain a carbonyl group with a second oxygen atom bonded to the carbonyl carbon. What differs between the two?

1. Both functional groups are built on the same carbonyl-plus-extra-oxygen framework, so the distinction lies in what that second oxygen attaches to. 2. The text explains: "In a carboxylic acid, the second oxygen atom also bonds to a hydrogen atom. In an ester, the second oxygen atom bonds to another carbon atom." 3. Neither group contains nitrogen, both clearly do contain a carbonyl group by definition, and esters are typically liquids (e.g. fruit-scented esters), not gases. 4. So the difference comes down to whether that second oxygen bonds to hydrogen (acid) or carbon (ester). _Source: OpenStax Chemistry Ch 20 "Organic Chemistry", p.1124 §20.3 Aldehydes, Ketones, Carboxylic Acids, and Esters_