In organic chemistry, an acetyl group is a functional group denoted by the chemical formula and the structure . It is sometimes represented by the symbol Ac
An acetyl group contains a methyl group () that is to a carbonyl (), making it an acyl group. 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.
The acetyl moiety is a component of many , including acetic acid, the neurotransmitter acetylcholine, acetyl-CoA, acetylcysteine, acetaminophen (also known as paracetamol), and acetylsalicylic acid (also known as aspirin).
Acetylation
Acetylation is the chemical reaction known as "ethanoylation" in the IUPAC nomenclature. It depicts a reactionary process that injects an acetyl functional group into a chemical compound. The opposite reaction is called "
deacetylation", and this is the
removal of the acetyl group. Therefore, the process of adding an acetyl group into a molecule is called
acetylation. An example of an acetylation reaction is the conversion of
glycine to
N-acetylglycine:
In biology
which perform acetylation on proteins or other biomolecules are known as acetyltransferases. In biological organisms, acetyl groups are commonly transferred from
acetyl-CoA to other organic molecules. Acetyl-CoA is an intermediate in the biological synthesis and in the breakdown of many organic molecules. Acetyl-CoA is also created during the second stage of cellular respiration (pyruvate decarboxylation) by the action of pyruvate dehydrogenase on
pyruvic acid.
are often modified via acetylation, for various purposes. For example, acetylation of by histone acetyltransferases (HATs) results in an expansion of local chromatin structure, allowing transcription to occur by enabling RNA polymerase to access DNA. However, removal of the acetyl group by histone deacetylases (HDACs) condenses the local chromatin structure, thereby preventing transcription.
In synthetic organic and pharmaceutical chemistry
Acetylation can be achieved by chemists using a variety of methods, most commonly with the use of
acetic anhydride or
acetyl chloride, often in the presence of a tertiary or aromatic
amine base.
Pharmacology
Acetylated organic molecules exhibit increased ability to cross the selectively permeable blood–brain barrier.
Acetylation helps a given drug reach the brain more quickly, making the drug's effects more intense and increasing the effectiveness of a given dose. The acetyl group in acetylsalicylic acid (aspirin) enhances its effectiveness relative to the natural anti-inflammatant
salicylic acid. In similar manner, acetylation converts the natural painkiller
morphine into the far more potent
heroin (diacetylmorphine).
There is some evidence that Acetylcarnitine may be more effective for some applications than L-carnitine.
Etymology
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.
See also
