CHEM301 F08 CA5B key

CHEM301 F08 CA5B key - CHEM301, Fall 2008 Dr. Ruder 1 Class...

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Dr. Ruder 1 Class Activity 5B Conformations of Alkanes Part B: Cyclohexane Compounds Model 1: Conformations of Cyclohexane Six membered rings have little ring strain and are the most stable of all the cyclic alkanes. Cyclohexane assumes a non-planar conformation with bond angles close to the preferred angle of 109.5 o . The two main conformations of cyclohexane are shown below. (note that the dotted line is not a bond) C C chair boat Questions 1. What are the names of the two main conformations of cyclohexane? Chair and boat 2. The chair conformation can be envisioned as being two triangles that are connected by two parallel lines, as shown above. Explain how the arrow shows conversion from the chair to the boat conformation. The arrow shows that the carbon is shifted upwards so that the whole “triangle” moves to make the boat conformation. 3. Using your model kit, build a model of cyclohexane in the chair conformation and a second model in the boat conformation. Check with a TA to make sure your model is correct. 4 . Rotate the left side of the chair in your model as indicated in Model 1 above to form the boat conformation. Compare to the model of the boat that you made. Are they the same? 5. Once your group reaches consensus on the above questions, predict whether the boat or the chair conformation is the most stable. Explain. The chair is more stable because there are only staggered interactions. The boat has eclipsed bonds which are less stable. Model 2: Axial and Equatorial The hydrogens in cyclohexane are oriented in either the axial (think axis of the globe) or equatorial (think equator) position. Each carbon has one axial and one equatorial hydrogen. Hax
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This note was uploaded on 02/17/2011 for the course CHEM 301 taught by Professor Sahli during the Fall '07 term at VCU.

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CHEM301 F08 CA5B key - CHEM301, Fall 2008 Dr. Ruder 1 Class...

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