Citronellol COSY spectrum

Citronellol. The COSY spectrum of citronellol (see the structural formula on p. 534) is a third example. The spectrum (Fig. 10.14) is rather complex in appearance. Nevertheless, we can identify certain important coupling interactions. Again, lines have been drawn to help you identify the correlations. The proton on C6 is clearly coupled to the protons on C5. Closer examination of the spectrum also reveals that the proton on C6 is coupled through allylic (four-bond) coupling to the two methyl groups at C8 and C9. The protons on Cl are coupled to two nonequivalent protons on C2 (at 1.4 and 1.6 ppm). They are nonequivalent, owing to the presence of a stereocenter in the molecule at C3. The splitting of the methyl protons at CIO by the methine proton at C3 can also be seen, al-... 

The following HETCOR spectrum is for citronellol. Use the structural formula on p. 534, as well as theDEPT-135 spectrum (Fig. 10.11) and the COSY spectrum (Fig. 10.14), to provide a complete assignment of all carbons and hydrogens in the molecule, especially the assignment of the carbon resonances at C2 and C4. 

FIGURE 9.15a gCOSY spectrum of citronellol (125 MHz). Analysis of the Full COSY Spectrum Shown in Figure 9.15a... 

Unfortunately, it is more difficult to use the COSY spectrum for the protons on the two methylene groups located at 2.10 and 2.05 ppm for the protons on C5 and C4. These protons have nearly the same chemical shifts values. The HETCOR spectrum shown on page 557 helps make the assignments. C5 has a C chemical shift of 27 ppm, which is close to the value of 25.1 ppm in citronellol for C5 (see the answer to Problem 3). C4 has a much larger value of 39 ppm which is close to the value in citronellol for C4 (37 ppm). 

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