1 (86)

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72 Chapter 4 CYCLOALKANES (b) = 64/36 = 1.78. Using the equation G° = - -1.36 log₁₀ (Section 2-1) for an equilibrium constant at room temperature (25°C), we get G° = - -0.34 kcal mol⁻¹. In Table 4-3 the axial/ equatorial free energy difference for an -OH substituent on cyclohexane is -0.94 kcal mol⁻¹. The difference derives largely from the fact that the ring in glucose is not a cyclohexane but an oxacyclohexane-a cyclic ether. Replacing a ring CH₂ group with an oxygen has several effects, including removal of the steric interactions associated with the hydrogens on the carbon, and introduction of two polar bonds whose dipoles can give rise to either attractive or repulsive interactions with the bonds of nearby substituted ring carbons. 42. Count carbons in the molecule. If there are 10, the molecule is a monoterpene; if 15, a sesquiterpene; if 20, a diterpene. (a) 10 carbons, monoterpene (b), (c), and (d) 15 carbons, sesquiterpene (e) 11 carbons, but only 10 in the contiguous molecular "skeleton"; monoterpene (f) 15, sesquiterpene (g) 10, monoterpene (h) 20, diterpene 43. CH₃ CH₃ (a) Alkenes (b) Alkenes (c) H₃C CH₃ H₂ OH Alcohol CHOH CH₂ CH₃ CH₃ Ester Alcohol Alkenes CH₃ CH₃ Alkenes CO₂CH₃ CH₃ Alcohol (d) CH₃ Ketone (e) (f) Ethers N HOCH2 OH Amine Alkenes Ethers Alcohols H₃C CH₃ CH₃ CH₃ (g) Anhydride CHOH Alcohol (h) CH₃ CH₃ Alkenes H₃C 44. Each isoprene unit can be set off by dashed lines: CH₃ (a) CH₃ CH₃ CH₂OH