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220 Chapter 11 ALKENES; INFRARED SPECTROSCOPY AND MASS SPECTROMETRY 33. 0 0 H V H > H > H The two alcohols are considerably more acidic ≈ 17) than the alkene 40 or so), which in turn is more acidic than the alkane (pKₐ > 50). 3-Cyclopenten-1-ol is slightly more acidic than cyclopentanol because of a small electron-withdrawing inductive effect exerted by the sp²-hybridized alkene carbon atoms. 34. (a) = 8 + 2 1 = 9; degree of unsaturation = (9 7)/2 = 1 bond or ring present. The integrated intensities reveal the pieces. δ = 1.8 (s, 3 H): CH₃, attached to an unsaturated functional group δ = 4.0 (s, 2 H): CH₂, most likely attached to Cl δ = 4.9 and 5.1 (singlets, each 1 H): Two alkene hydrogens Thus, you have and attached to two H's. There are three ways to attach the four groups around the double bond. CH₃ CH₂Cl CH₃ H CH₃ H H H H CH₂Cl CICH₂ H In the first two compounds, all the NMR signals should show substantial couplings. H Only the third compound will show a spectrum as simple as A (remember that = C couplings H are typically very small whereas cis and trans H-C=C-H couplings are large); it is the correct answer. (b) = 10 + 2 = 12; degree of unsaturation = (12 8)/2 = 2 bonds and/or rings. The NMR shows the following: δ = 2.1 (s, 3 H): CH₃, next to an unsaturated functional group δ = 4.5 (d, 2 H): attached to oxygen, split by one H δ = 5.3 and 5.9 (m, 2H and 1H): the internal H downfield of the other two, typical of a terminal ethenyl group; the extensive splitting of the δ 5.9 signal suggests an adjacent CH₂ [compare Figure 11-11(b) in the text] The pieces are and so far: C₄H₈O, leaving a C and an 0 to add in, and one more bond (a ring would be impossible). So let them be giving the final solution: (c) = 8 + 2 = 10; degree of unsaturation = (10 8)/2 = 1 bond or ring. δ = 1.3 (doublet, 3 H): Most likely δ = 1.6 (broad singlet, 1 H): Perhaps OH? δ = 4.3 (quintet w/fine splitting, 1 H): Probably CH-OH, four immediate neighbors to the CH (not including the OH) δ = 5.1 and 5.3 (one narrow doublet and one wider doublet, 1 H each): Alkene hydrogens, one cis-and one trans to a third alkene hydrogen