The carbonyl center of an acyl radical has one non-bonded electron with which it forms a chemical bond to the remainder (denoted with the letter R) of the molecule.

However, removal of the acetyl group by histone deacetylases (HDACs) condenses the local chromatin structure, thereby preventing transcription.

In similar manner, acetylation converts the natural painkiller morphine into the far more potent heroin (diacetylmorphine).

[12] The term "acetyl" was coined by the German chemist Justus von Liebig in 1839 to describe what he incorrectly believed to be the radical of acetic acid (the main component of vinegar, aside from water), which is now known as the vinyl group (coined in 1851); "acetyl" is derived from the Latin acētum, meaning "vinegar."

When it was shown that Liebig's theory was wrong and acetic acid had a different radical, his name was carried over to the correct one, but the name of acetylene (coined in 1860) was retained.