the boa Th8mm2gaornte16aeome-fthe 。 xane has axial and equatorial hydrogen draw chair cyclohexanes,follo 1.)Draw the carbon chair n th as two types of hyd oral 6 H perpendicular to the prindple molecular axis 3】Draw the C1andc4eqy A. 4.)Draw the remainin Sgiormtydlogengtntercomvertaaaland 4-4 Substituted Cyclohexanes clohexanes are not ngr6pbemonoontewba2heegap 苹一 g"m oidnsomreneo9 33 The boat form of cyclohexane is flexible and actually represents a transition state between two slightly more stable twist-boat (or skew￾boat) conformations. The stabilization of the twist forms to the boat form is about 1.4 kcal mol-1, The activation energy for interconversion of the chair form and boat forms is 10.8 kcal mol-1. Normally cyclohexane exists primarily as the chair confomer with very small amounts of the twist boat form and no actual boat form. Cyclohexane has axial and equatorial hydrogen atoms. In the chair form, cyclohexane has two types of hydrogens: •Axial 6 H parallel to the principle molecular axis •Equitorial 6 H perpendicular to the principle molecular axis Two draw chair cyclohexanes, follow these steps: 1.) Draw the carbon chair. 2.) Add the axial hydrogens. 3.) Draw the C1 and C4 equitorial hydrogens. 4.) Draw the remaining equatorial hydrogens. Conformational flipping interconverts axial and equatorial hydrogens. Starting with a chair form having C1 down and C4 up, the boat form can be reached by flipping C1 up. If in returning to the chair form, C4 is flipped down, rather than C1, the effect is to interconvert the axial and equitorial hydrogens on the cyclohexane molecule: The energy of activation for this conversion is 10.8 kcal mol-1 which is very low, and at room temperature this interconversion occurs approximately 100,000 times per second. When substituents replace one or more hydrogens, one conformer may be more stable than the other, affecting both stereochemistry and reactivity. 4-4 Substituted Cyclohexanes Axial and equatorial methylcyclohexanes are not equivalent in energy. In methylcyclohexane, the conformer having the methyl group in an equatorial position is more stable by about 1.7 kcal mol-1. The 1,3-diaxial interaction is the same as the result in the gauche conformation of butane