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Solutions to Problems 297 CH₃ C CH₂ CH (b) CH₂ CH₂ limonene Via a Diels-Alder concerted cycloaddition reaction CH C CH₃ CH₂ CH₃ 69. + limonene New Bond + H CH₃ CH₃ H Alternatively, + -H+ pinene New bond 70. In each case the process involves promotion of an electron in the highest occupied molecular orbital (n or π) to the lowest unoccupied molecular orbital (e.g., π*). Use subscripts when there is more than one orbital of a given type. (a) TT n (alternatively, (b) n π* (alternatively, π₂ π₃); (c) n π*; (d) n π* (more specifically, n π₃*); (e) n (alternatively, (f) π₃ 71. These molecules contain only σ and n electrons, and their lowest unoccupied molecular orbitals are σ*. The energy gaps between these orbitals are large, resulting in UV absorptions only at wavelengths shorter than 200 nm. 72. 1.95/(2 X 10⁻⁴) = 9750; 0.008/(2 X 10⁻⁴) = 40 Then 73. + CH₃CCH₃ 1.3 4.8 - 6.2 OH 2.4 The new compound may be derived from ionization of the allylic alcohol upon extended contact with acid: + OH₂ + + H2O: 1.70 and 1.79 5.45 (triplet) 4.10 (doublet)