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Cyclohexane: Isomers & Synthesis

Instructor: Korry Barnes

Korry has a Ph.D. in organic chemistry and teaches college chemistry courses.

This lesson will focus on a specific class of cyclic organic structures called cyclohexane derivatives. We will feature isomers of cyclohexane compounds and how they are synthesized.

Roller Coasters and Molecules

Are you one of those people that likes riding on roller coasters at the theme park? Have you ever been on one that goes upside down in a loop? In general, a loop can kind of be thought of as a 'cycle' of sorts. Did you know that some organic compounds can be referred to as cyclic and kind of resemble a loop of sorts? These types of compounds result when we take two ends of a molecule and bond the ends together to create the cycle or loop, very similar to a loop on a roller coaster. The topic of this lesson is a specific kind of 'loop' known as cyclohexane. We will be studying the derivatives and isomers of cyclohexane as well as how they can be synthesized in the lab. Let's go around the loop!

What is Cyclohexane?

Cyclohexane is an organic compound that is composed of carbon and hydrogen atoms and is a cyclic structure with the ring being constructed of six carbon atoms bonded together. The bonds in cyclohexane are all single bonds, and the shape resembles a hexagon when it's drawn as a bond-line structure.


Cyclohexane is a cyclic organic compound composed of six carbon atoms and contains only single bonds
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Isomers of Cyclohexane

Although cyclohexane is an important compound, it gets more interesting when we start to decorate the ring with other substituents (atoms or groups of atoms). This results in derivatives and isomers of cyclohexane. For example, let's consider both 1,2-dichlorocyclohexane and 1,4-dichlorocyclohexane. Notice how both compounds contain a cyclohexane ring and each have two chlorine atoms. They differ in how the chlorine atoms are bonded to the ring. This type of relationship represents what are called constitutional isomers, which are compounds that have the same type and number of atoms but differ in the way the atoms are bonded to one another. Another way stating it is that the compounds have the same chemical formula, but different atom connectivity.


1,2- and 1,4-dichlorocyclohexane are constitutional isomers of one another
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What if we had a case in which the cyclohexane ring had two alcohol (-OH) groups that were bonded to the same positions on the ring, but they had a different spatial orientation relative to one another? Isomers of a compound that differ only in their three-dimensional (spatial) orientation are called stereoisomers. This is the case with cis-1,2-dihydroxycyclohexane and trans-1,2-dihydroxycylohexane. Notice how the two alcohol groups are on the same face of the ring in one case (two dashed bonds) but are on opposite faces (one wedged bond, one dashed bond) in the other.


Isomers that differ from one another by their three-dimensional orientation are called stereoisomers
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Synthesis of Cyclohexane Isomers

Now that we know how to recognize cyclohexane and some of its isomers and derivatives, let's discuss how some of these compounds can be made synthetically in the lab. For example, cyclohexanol can be oxidized to provide cyclohexanone in a very simple reaction that is commonly run in undergraduate organic chemistry labs. The common way to promote the reaction is with an inorganic reagent called sodium dichromate which also requires an acid source.


Cyclohexanol can be oxidized to form cyclohexanone as the product
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