Acyl Group: Definition & Structure

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

Acyl groups are one of organic chemistry's functional groups. In this lesson we will learn what an acyl group is, examples of acyl group structures, and how they are used in the body.

General Structure

Our body goes through a variety of processes in order to make energy. The structure of the compounds involved in these processes is important to understand in order to understand how the reactions occur. One of these important reactions is Acetyl-CoA in the citric acid cycle. Acetyl-CoA includes an acyl group, one of the functional groups in organic chemistry.

In organic chemistry, there are a variety of groups, called functional groups. Functional groups share common characteristics and IUPAC names. One of these functional groups is the acyl group. The acyl group is a fairly broad term which refers to any RCO- group.

The 'R' is any carbon chain, from 1 CH3 up to hundreds of CH2 ending in a CH3. The 'R' chain can also have other substituents, functional groups, or double or triple bonds.

The acyl group general structure
Acyl general structure

The carbon in the acyl group is double bonded to the oxygen. And the fourth bond and that carbon will be anything, except for an OH. If it is a RCOOH, then it is put into the carboxylic acid group.

Examples

Acyls are further broken into additional groups:

  • Aldehydes
  • Ketones
  • Esters
  • Amides
  • Acetyl halides

Aldehydes are the simplest acyls, the fourth carbon bond is to a hydrogen:

Aldehyde structure
Aldehyde

Ketones put another R group on the other side of the carbon:

Ketone structure
Ketone

Esters are similar to carboxylic acids except that instead of an OH it is an OR group:

Ester Structure
Ester

Acyl amides have an amine group attached, such as NH2, NHR or NR2.

An acyl amide with an NHR attached
Amide

Acyl halides put a halogen (Cl, Br, F, I, or At) onto the carbon:

An acyl halide, the x refers to any halide
halide

Function and Examples of Acyls

Typically, acyls are nucleophilic because the carbon-oxygen bond draws electrons away into the oxygen. This makes the other carbon bonds lacking in electrons. So, electrophilic compounds can attack and be added to the acyl or substitute out for another group (forming a different acyl group).

An important acyl group in our bodies is acetyl CoA (or Acetyl coenzyme A). Acetyl CoA is the finished product after glycolysis (the breakdown of sugar for energy) and brings the acetyl group to the citric acid cycle in order to form more energy. Based on the name we can tell that there will be an acetyl group, so let's take a look at the structure:

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