Difference Between Acetate and Triacetate

The key difference between acetate and triacetate is that acetate is a single acetate ion, whereas triacetate is a combination of three acetate ions.

The terms acetate and triacetate are usually used to describe cellulose diacetate and cellulose triacetate molecules.

CONTENTS

1. Overview and Key Difference
2. What is Acetate
3. What is Triacetate
4. Acetate vs Triacetate in Tabular Form
5. Summary – Acetate vs Triacetate

What is Acetate?

Acetate or cellulose acetate is a type of cellulose that contains two acetate groups bound to a glucose molecule. It can refer to any acetate ester of cellulose, but specifically to cellulose diacetate. This substance has applications in film base in photography and as a component in some coatings.

Cellulose Acetate Production

When considering the production of cellulose acetate, it is derived from cellulose through the initial deconstruction of wood pulp into a pure fluffy white cellulose product. However, in order to get a good product, we can use special qualities of pulps, such as dissolving pulps. The cellulose reacts with acetic acid or acetic anhydride in the presence of sulfuric acid. Sulfuric acid controls and partially hydrolyzes to get a less substituted form of cellulose that is substituted with acetate.

What is Triacetate?

Triacetate or cellulose triacetate is a type of cellulose acetate consisting of three acetate groups per glucose molecule. We can abbreviate this substance as CTA or as TAC. It forms from the reaction between cellulose and a source of an acetate ester such as acetic anhydride. This material is common in use for the production of cellulose fibers and film base. Chemically, this substance is similar to cellulose acetate but is different because about 92% of the hydroxyl groups in cellulose triacetate are acetylated.

Triacetate Production

When considering the production of triacetate, it is obtained from cellulose through the acetylation of cellulose with acetic acid or acetic anhydride, where sometimes a combination of both acetic acid and acetic anhydride are used. This acetylation step can convert the hydroxyl groups in the glucose molecule into acetyl groups. This makes the cellulose polymer material easily soluble in organic solvents. We can observe that cellulose acetate can dissolve in a mixture of dichloromethane and methanol. However, there is a finishing step as well. This finishing process is named as S-finishing or surface saponification, and it removes a part or all the acetyl groups from the surface of the fiber, leaving them with a cellulose coating. This finishing step can reduce the tendency of the fibers to obtain a static charge.

What is the Difference Between Acetate and Triacetate?

The terms acetate and triacetate are usually used for cellulose diacetate and cellulose triacetate molecules. The key difference between acetate and triacetate is that acetate is a single acetate ion, whereas triacetate is a combination of three acetate ions. In addition, acetate is produced from the reaction between acetic acid or acetic anhydride in the presence of sulfuric acid under controlled conditions, while triacetate is the reaction between acetic acid or acetic anhydride or a combination of both.

The following infographic summarizes the difference between acetate and triacetate in tabular form.

Summary – Acetate vs Triacetate

The terms acetate and triacetate are usually used for cellulose diacetate and cellulose triacetate molecules. The key difference between acetate and triacetate is that acetate is a single acetate ion, whereas triacetate is a combination of three acetate ions.

Reference:

1. “Cellulose Acetate.” Wikipedia, Wikimedia Foundation, 10 May 2021.

Image Courtesy:

1. “Cellulose acetate preparation” By Alnokta – Own work (Public Domain) via Commons Wikimedia
2. “Cellulose triacetate” By Edgar181 – Own work (Public Domain) via Commons Wikimedia