Hello, students, in the previous module we talked about the flipping of the chair conformation and I told you that there are going to be several more conformations those comes in between these two extreme chair conformation.
So, let’s actually study the conformational analysis of Cyclohexane. So, what are those several more conformations that we get during the process of flipping. So, this is nothing but a chair conformation and in the process of flipping the rotation of the carbon, carbon sigma bond first convert that into one of the momentary arrangement like this called as half chair conformation. The further rotation triggers the flipping of the bonds and converts this half chair into this kind of conformation called a twist boat. Where this twist boat on further rotation gets converted to a boat conformation and this boat further gets converted into new conformation which is again like a twist boat just like a mirror image of c. Whereas this twist boat further gets converted to a half chair conformation and ultimately this half chair conformation gets converted to the other extreme end of a chair conformation.
Well, if we study the energy changes taking place during the flipping of the chair conformation the graphical representation that we get and what you simply call as the conformational analysis of Cyclohexane. So, let’s learn it actually the chair conformation. So, this is the graphical representation as we have studied earlier the chair conformation of the Cyclohexane is the most stable hence least energetic. Well, in the process when the flipping starts this (a) form that is chair conformation gets converted to the next one which is nothing but half chair, where this half chair and the chair conformation are separated by the energy barrier of 10 kilo calorie. This half chair in a flipping further gets converted to, that is (c) one which is nothing but a twist boat and this twist boat is higher in energy as compared to chair conformation by 5.5 kilo calorie. Well, further flipping pushes this twist boat into the new conformation that is the boat conformation. Well, this boat conformation is again important for us with the examination point of view. But one information that we need to know this boat conformation is separated by the energy barrier in comparison to a chair conformation by 6.9 kilo calorie. Why such a large difference in the energy between the chair and the boat. Let’s look at this, in this boat conformation if you observe these 8 hydrogen atoms which are highlighted. These 8 hydrogen atoms come exactly behind each other if you observe them in the Newman projection, which means due to the eclipsing of these bonds this boat conformation exhibits a torsional strain and not only that if you observe this two H’s now, which is pointing towards each other they start creating a steric strain. And since they look like a pole it is sometime also called as a Flagpole interaction. Due to presence of the steric strain and the torsional strain this boat conformation is having 6.9 kilo calorie higher than the chair conformation. Well, this boat as we have seen earlier then gets converted again to a twist boat and this twist boat in a flipping process further gets converted to a half chair and ultimately we get the extreme end, that is nothing but a chair conformation.
So, this analysis gives us clarification about what are the various conformations that we get in a process of a flipping of a chair conformation.
That’s it from this module. Thank you so much.
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