Camphor shifts 331

Studies in surface-inactive electrolyte solutions with various organic compounds (cyclohexanol, 1-pentanol, 2-butanol, camphor, tetra-buthyl ammonium ion, TBN+) show that the adsorption-desorption peak shifts to more negative potentials in the order (0001) < (1010) < (1120) this was explained by the increasing negative value of Eff=0 in the same direction.259 629-635... 

Adsorption of various organic compounds (e.g., cyclohexanol, adamantanol-1, and camphor) has been studied at a renewed Sn + Pb alloy/electrolyte interface.820-824 The time variation of the surface composition depends on the solution composition, the nature and concentration of the surface-active substance, and on E. The " of cyclohexanol for just-renewed Sn + Pb alloys shifts toward more negative E with time, i.e., as the amount of Pb at the Sn + Pb alloy surface increases. 

Figure 5.5 shows the heteronuclear 2Dy-resolved spectrum of camphor. The broad-band decoupled C-NMR spectrum is plotted alongside it. This allows the multiplicity of each carbon to be read without difficulty, the F dimension containing only the coupling information and the dimension only the chemical shift information. If, however, proton broad-band decoupling is applied in the evolution period tx, then the 2D spectrum obtained again contains only the coupling information in the F domain, but the F domain now contains both the chemical shift and the coupling information (Fig. 5.6). Projection of the peaks onto the Fx axis therefore gives the Id-decoupled C spectrum projection onto the F axis produces the fully proton-coupled C spectrum.

These observations were applied by Dimitrov, Hesse and coworkers. On stndying ozonization of a series of allylic and homoallylic alcohols prepared from (+) camphor and (—) fenchone, they were able to isolate a certain number of ozonides and to obtain the O NMR spectrum of the diastereomeric mixture of one of them, i.e. derivative 15, whose structure and O NMR chemical shifts (5, ppm) are shown below. 

In accordance with the proportionality (3.8 a), the magnitude of the pseudocontact shift, which predominates for lanthanide shift reagents, decreases with the distance of nucleus i from the paramagnetic ion. Thus, C-9 of camphor is shifted more than C-10 on addition of the europium chelate. Often, the crude approximation (3.8 a) is a valuable assignment aid. 

Carbonyl compounds (e.g. camphor in Fig. 3.7(c)) show smaller isotropic shifts than comparable alcohols (e.g. isoborneol in Fig. 3.7(b)). 

The 13C chemical shifts of the parent compounds of camphor and its derivatives are given with the following structures ... 

Table 5.5. Structure and 13C Chemical Shifts (<5C in ppm) of Camphor and Related Compounds. 

A tandem 1,4-addition-Meerwein-Ponndorf-Verley (MPV) reduction allows the reduction of a, /i-unsaturated ketones with excellent ee and in good yield using a camphor-based thiol as reductant.274 The 1,4-addition is reversible and the high ee stems from the subsequent 1,7-hydride shift the overall process is thus one of dynamic kinetic resolution. A crossover experiment demonstrated that the shift is intramolecular. Subsequent reductive desulfurization yielded fiilly saturated compounds in an impressive overall asymmetric reductive technique with apparently wide general applicability. 

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