Greeting,
This post explores the flexibility of cyclohexane and the amazing geometric shapes which form. If you take a ball and stick model of n-hexane, remove a stick & H ball at one end and one more H ball at the other end, you are close to forming a ball and stick model of cyclohexane. Now, insert the "bare" stick from one end into the open hole on the other end, and with some careful twisting you will have your model.
Straight and branched-chain alkane molecules always afford complete rotation about every bond. This is clearly not the case with cyclohexane, assuming that you have made your ball and stick model. The actual required tetrahedral geometry of each carbon atom (in relation to its 2 adjacent C atoms and bonded H atoms) puts an enormous strain on the cyclohexane structure until you arrive at one of the two possible stable molecular conformations; chair and boat. The chair conformation is more "spread out" or elongated and is much more stable (lower potential energy) than the boat shape: Do you know why? See Form, Part 6 for a clue. The boat and chair confirmations are actually resonating with each other, but chemists have discovered that the chair arrangement dominates; i.e. Cyclohexane is in the chair form 99.9% of the time, on average. The following chart displays the points from above.
Note the comment about group repulsion for the boat ball-and-stick model. The CH2 groups at the left and right sides are much closeer than they appear to be in the ball-and-stick model! The much greater stability of the chair resonance structure results in that form existing 999 seconds for each 1000 second period of time.
That's all for now. My next post will explore the many Alkanes which make up several of the petroleum fuels we commonly use.
Thank you for reading.
A Publication of http://ExcellenceInLearning.biz
This post explores the flexibility of cyclohexane and the amazing geometric shapes which form. If you take a ball and stick model of n-hexane, remove a stick & H ball at one end and one more H ball at the other end, you are close to forming a ball and stick model of cyclohexane. Now, insert the "bare" stick from one end into the open hole on the other end, and with some careful twisting you will have your model.
Straight and branched-chain alkane molecules always afford complete rotation about every bond. This is clearly not the case with cyclohexane, assuming that you have made your ball and stick model. The actual required tetrahedral geometry of each carbon atom (in relation to its 2 adjacent C atoms and bonded H atoms) puts an enormous strain on the cyclohexane structure until you arrive at one of the two possible stable molecular conformations; chair and boat. The chair conformation is more "spread out" or elongated and is much more stable (lower potential energy) than the boat shape: Do you know why? See Form, Part 6 for a clue. The boat and chair confirmations are actually resonating with each other, but chemists have discovered that the chair arrangement dominates; i.e. Cyclohexane is in the chair form 99.9% of the time, on average. The following chart displays the points from above.
Note the comment about group repulsion for the boat ball-and-stick model. The CH2 groups at the left and right sides are much closeer than they appear to be in the ball-and-stick model! The much greater stability of the chair resonance structure results in that form existing 999 seconds for each 1000 second period of time.
That's all for now. My next post will explore the many Alkanes which make up several of the petroleum fuels we commonly use.
Thank you for reading.
A Publication of http://ExcellenceInLearning.biz