Inhibitors: Definition & Types

Inhibitors: Definition & Types
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  • 0:00 Inhibitor Defined
  • 1:00 Why Are Inhibitors Useful?
  • 2:36 Common Chemical Inhibitors
  • 5:08 Lesson Summary
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Lesson Transcript
Instructor: Trista Robichaud

Dr Trista has a PhD in Biochemistry and loves to teach college biology and chemistry.

In this lesson, we introduce the concept of a chemical inhibitor, how chemists use them to stop or modify reactions, and common types of chemical inhibitors you may encounter in everyday life.

Inhibitor Defined

A chemical inhibitor is a reactant or process that slows or halts a chemical reaction. In order to understand this, imagine a chemical reaction is like driving a car. You start driving at 'reactants' and continue on to your destination, or 'products'. While driving, you press the accelerator to go faster, and you apply the brake to slow down. To inhibit means to prevent or slow down and in our car analogy, the brakes are a vehicle inhibitor. In chemistry, inhibitors are molecules that slow down or stop a chemical reaction from taking place.

In general, there are two kinds of inhibitors, reversible and irreversible inhibitors. Reversible inhibitors slow down a chemical reaction, but do not stop it completely. Irreversible inhibitors prevent an unwanted reaction from occurring.

Why Are Inhibitors Useful?

Chemical inhibitors are useful for a number of reasons. For one thing, reaction products often go on to create an undesired new substance in a side reaction. Think of it like driving your car off a mountain road. This doesn't result in reaching your destination or product. In addition, some reactions put out lots of heat and extra heat may cause safety hazards, your car's engine may catch fire, or increase the likelihood of unwanted side reactions, such as a car crash. Inhibitors also prevent chemical damage or decay in finished products. An anti-rust coating on your car is a good example of this.

In polymer chemistry, reaction inhibitors are used to modify the properties of the final polymer product as well as to prolong usefulness. Did you know that the polyethylene used to make milk jugs as well as plastic bags is made from the same reactants? Longer polymer chains form into strong thin films. If you bubble oxygen gas through the reaction vessel, a thicker, softer plastic is formed. Plasticizers and crosslinkers are other classes of compounds added to a polymer chemistry reaction to alter how flexible or rigid the final product will be.

As another example, silver metal is very reactive, so silver jewelry is often coated with rhodium metal or a clear polymer to prevent the formation of dark colored silver sulfides, which is often referred to as tarnish. The polymer coating is an inhibitor.

Common Chemical Inhibitors

There are many different types of chemical inhibitors. Some of the more common types include corrosion inhibitors, reversible and irreversible enzyme inhibitors, microbial inhibitors and preservatives, and UV stabilizers.

Corrosion inhibitors specifically prevent acid or oxidation damage to metals or metal alloys. These are vitally important in industrial chemical processes, where large amounts of acids may be created as part of a reaction. Usually, corrosion inhibitors are applied to a surface to prevent that surface from being damaged.

In biochemistry, an enzyme is a protein catalyst for a chemical reaction. There are three kinds of reversible enzyme inhibitors: competitive inhibitors, uncompetitive inhibitors, and noncompetitive inhibitors, which are classified according to where they bind to the enzyme. Irreversible enzyme inhibitors, on the other hand, bind enzymes covalently, inactivating them. Enzyme inhibitors are frequently utilized prescription drugs and include protease inhibitors, sulfa drug inhibitors, natural inhibitors used in embryonic development, and many other interesting enzymatic inhibitors.

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