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Alkynes: Properties, Uses, Formula & Examples

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  • 0:05 What Are Alkynes?
  • 1:13 Properties of Alkynes
  • 2:02 Alkynes - Uses and Examples
  • 3:41 Lesson Summary
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Lesson Transcript
Instructor: Nissa Garcia

Nissa has a masters degree in chemistry and has taught high school science and college level chemistry.

Alkynes are identified as organic chemical compounds that have triple bonds in their chemical structure. They are organic compounds that are important in various industrial applications. In this lesson, we will learn all about alkynes.

What Are Alkynes?

What are alkynes and how do we know that a chemical compound is an alkyne? Alkynes are hydrocarbons, which are organic chemical compounds containing carbon (C) and hydrogen (H) atoms, and the feature that makes them recognized as alkynes is the presence of triple bonds.

Chemical compounds that have triple and double bonds in their chemical structures are referred to as unsaturated. Because alkynes have triple bonds in their chemical structure and consist of carbon and hydrogen atoms, they are unsaturated hydrocarbons.

Here we can see the general chemical structure of alkynes (RCCR'):

General Formula of Alkynes and Example

The carbon (C) atoms shown below are bonded together by a triple bond. We can also see two side groups, R and R', which are bonded to the carbon (C) atoms. The side groups R and R' could be any group that consist of hydrogen and/or carbon atoms. In this example of an alkyne, there is a triple bond between two carbon (C) atoms and the side groups R and R' are both -CH sub 2CH sub 3.

Properties of Alkynes

What do alkynes physically look like? Are they usually solids, liquids, or gases? In general, alkynes are in gaseous form and they are soluble in organic solvents, like benzene and acetone. They are, however, insoluble in water. Another property of an alkyne is that, if you try to burn it, the flame results will turn out to be a sooty flame.

Let's compare the acidity and boiling point of alkynes to the other hydrocarbons, alkenes (hydrocarbons that have double bonds) and alkanes (hydrocarbons that are only made of single bonds). In general, alkynes are more acidic than alkenes and alkanes, and the boiling point of alkynes also tends to be slightly higher than alkenes and alkanes.

Alkynes - Uses and Examples

Alkynes have various industrial applications. Let's take a look at a few examples of common alkynes and what they are used for.

Acetylene, also referred to as ethyne, is one of the most well-known and widely used alkynes. Acetylene is very useful because it can undergo several chemical reactions that are needed in manufacturing products in different industries.

Let's think about plastic. We use plastic products for so many things, and plastic is made using a compound called polyethylene. Acetylene is an important raw material in the chemical industry to produce polyethyelene. Have you ever heard of an acetylene torch? This type of torch is used to cut and weld steel, and it uses acetylene as fuel.

Another alkyne is propyne, also known as methylacetylene, which is commonly used as a substitute for acetylene as fuel for welding torches. It is also being investigated as possible fuel for rockets in spacecraft.

There are also compounds that have alkynes in their chemical structure that have interesting uses. When we say they have alkynes, it means that these compounds have carbon-carbon triple bonds in their chemical structure.

There are compounds containing alkynes (carbon-carbon triple bonds) that you may be familiar with, like ethinyl estradiol and norethynodrel. These two compounds are used in oral contraceptives, and if you look closely at the drug information label, you may see these two there.

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