What is an Acetyl Group? - Definition & Structure

Instructor: David Jones

David has taught General and Organic Chemistry and has a master's degree in Chemistry.

In this lesson, you will learn all about the acetyl group, including what it is, its specific structure, and some of the common molecules that contain it.

A New Language

Have you ever traveled to a foreign country? Have you tried ordering your food in a new language? Or, asking where the bathroom is? If you have, and if you did not speak that language well, you may have gotten blank looks in response. It is in those moments that you realize how important language is to everything you do in life.

Organic chemistry is much the same. If you don't know the language, you might not get very far. Sometimes you just need a science dictionary to help remind you what all of the new terms mean!

The Acetyl Group


An acetyl group is first and foremost a moiety. A moiety is simply a part of a molecule. So, an acetyl group is a part of a molecule and is not a molecule unto itself. Similarly, an arm or a leg is a part of a body, but could not stand on its own to be its own body.

Secondly, an acetyl group is a part of a larger family of moieties called an acyl group. An acyl group is made up of two parts. First is the carbonyl group. A carbonyl group is a carbon double bonded to an oxygen. The second part is an alkyl group, which is simply a moiety made up of carbons and hydrogens.


Just like the acyl group, the acetyl group is made up of two parts. The first part, like the acyl, is a carbonyl group made up of a carbon double bonded to an oxygen. The second part, however, is more specific. Since the acetyl group is a type of acyl group, we know that this second part must be an alkyl group, but it is more specific. In this case, it is a methyl group, which is simply a carbon with three hydrogens (CH3).

Acetyl group
Acetyl group


Depending on what the acetyl group is bonded to, all sorts of molecules can be formed using this moiety. One of the most common is acetic acid, the main component of vinegar, made by attaching an acetyl group to an OH group.

Acetic acid
Acetic acid

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