Doublet alcohol

The first molecule to be studied in this manner, methyl alcohol, is a rather special case because of the very small moment of inertia of the OH group. Consequently, most of the doublets are so widely split that only one member has been observed. Nevertheless a very precise barrier value was obtained from the analysis. 

In Figure 10.23, the major peak at 5 ppm is a singlet, the major peak at 4.5 ppm is a septet (split into seven peaks), and the major peak at 1.5 is a doublet. The spectrum is that of either n-propyl alcohol, isopropyl alcohol, or acetone. Decide which and justify your decision. 

The red thermally unstable crystals are soluble in organic solvents. Since the complex is extremely sensitive to nucleophiles, traces of moisture and alcohols have to be removed from all solvents before use. The complex must be stored under nitrogen below -20°. IR Vqq at 2070 (m), 1952 (vs, br), 1942 (vs, br) cm 1 in pentane, H NMR (TMS, C6D6, 60 MHz) tsjch3 at 9.93 ppm (singlet), tCHj at 8.11 ppm (singlet), rCtH< at 2.68 ppm (doublet) + 3.08 ppm (doublet). 

Arnold and Hobert (231) studied the chemisorption of ferrocene, (C5H5)2Fe, on a silica surface from an alcohol solution. Ferrocene itself shows a symmetric quadrupole splitting. After chemisorption this doublet is no longer symmetric, and the authors explain this in terms of a Gol danskii-Karyagin effect, where the iron atoms in the adsorbed state have a larger mean square displacement perpendicular to the silica surface than parallel to it. 

The 1II NMR corroborates diis conclusion since two vinyl protons are observed both in the reactant and product however, a new two-proton doublet appears at 4.155 for die newly produced allylic methylene group. The acid O-H proton is moved far upheld as well. The coupling constants of die vinyl protons (./ = 16 Hz) show the starting compound to be dans, and die large splitting for the downheld vinyl doublet of die product (J = 16 Hz) shows die trails stereochemistry to be maintained in die unsaturated alcohol product. Moreover die splitting between the methylene group and the upheld vinyl proton clearly supports its allylic position. 

Alcohol spectra were obtained in chloroform-d and are referenced to internal tetramethylsilane. Cation spectra are referenced to tetramethylsilane contained in a capillary inside the NMR tube. The methyl group signal for the methyl-substituted carbonium ions (in nitromethane, sulfuric acid, and trifluoroacetic acid) was a doublet (J = 7 Hz). The methyne proton for these same carbonium ions appears as a quartet (J = 7 Hz). For the phenyl-substituted and unsubstituted carbonium ions, the methyne proton and methylene proton signals (respectively) were singlets. 

Cholesterol (Fig. 1.20) is a steroid, the same rigid five-ring backbone used for the mammalian sex hormones. There are only two functional groups an olefin (C-5, C-6) and an alcohol (C-3). The bulk of the molecule can be described as saturated hydrocarbon. There are five methyl groups two are attached to quaternary carbons so they should appear as singlets and three are attached to CH carbons so they should appear as doublets. Most of the protons in the A, B, and C rings can be described as axial or equatorial due to the rigid,... 

Figure 11.30 shows a portion of the HMBC spectrum of Product 2, including the alcohol region in both dimensions (3.2-4.4 in F2 = H and 67-85 ppm in F = 13C). The HSQC peaks are superimposed and shown in parentheses, and the resonances are shown above or below these peaks with an expansion of the ddd at 4.15 ppm. One-bond artifacts are clearly visible in the HMBC spectrum as wide doublets centered on the position of the 13C-decoupled HSQC crosspeaks (compare to the diagram in Fig. 11.11). In addition a fat HMBC crosspeak is observed between the new lH resonance at 4.15 ppm in F2 and the C-17 13C resonance at 82 ppm in F (Fig. 11.30, lower left side). This means that the CH-OH proton at the position of oxidation is two or three bonds away from C-17 Of the three possibilities (7, 11, and 15), it must be H-15. H-11 would be four bonds away and...

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