1-Propanol decoupled

Complementary Examinations Peak intensity data (obtained from the spectrometer) may be of value in comparative studies (Lundquist et al 1981) In some cases, peak assignments derived from model compound studies may be verified by decoupling experiments (Lundquist 1979a, 1980, Hauteville et al 1986) or by the recording and examination of difference spectra (Lundquist and Olsson 1977, Brunow and Lundquist 1980, Lundquist et al 1981, Adler et al 1987) 2-D NMR spectroscopic methods may also be used for the same purpose (Lundquist and Stern 1989, Ede et al 1990) Thus, it was concluded from 2-D COSY H NMR experiments that the peak at d 2 62 in Fig 5 3 1 is partly due to benzylic protons in 3-aryl-l-propanol units (Lundquist and Stern 1989)... 

Power, G., Johari, P., and Vij, J. K. (2002) Effects of ions on the dielectric permittivity and relaxation rate and the decoupling of ionic diffusion from dielectric relaxation in supercooled liquid and glassy 1-propanol, J. Chem. Phys. 116, 419-4201... 

Figure 4.5 is a second example of a proton-decoupled spectrum. Notice that the spectrum shows three peaks, corresponding to the exact number of carbon atoms in 1-propanol. If there are no equivalent carbon atoms in a molecule, a C peak will be observed for each carbon. Notice also that the assignments given in Figure 4.5 are consistent with the values in the chemical shift table (Fig. 4.1). The carbon atom closest to the electronegative oxygen is farthest downfield, and the methyl carbon is at highest field.

Off-resonance decoupling can be a great help in assigning spectral peaks. The off-resonance-decoupled spectrum is usually obtained separately, along with the proton-decoupled spectrum. Figure 4.8 shows the off-resonance-decoupled spectrum of 1-propanol, in which the methyl carbon atom is split into a quartet and each of the methylene carbons appears as a triplet. Notice that the observed multiplet patterns are consistent with the n -I- 1 Rule and with the patterns shown in Figure 4.3. If TMS had been added, its methyl carbons would have appeared as a quartet centered at 5= 0 ppm. 

FIGURE 9.30 (a) The broadband proton-decoupled NMR spectrum of 1-chloro-2-propanol. (b) These three spectra show the DEPT NMR data from 1 -chloro-2-propanol (see Section 9.11D). (This will be the only full display of a DEPT spectrum in the text. Other NMR figures will show the full broadband proton-decoupled spectrum but with information from the DEPT NMR spectra indicated near each peak as C, CH, CH2, or CH3.)... 

Figure 5.10. The (a) undecoupled (coupled) C NMR and (b) proton decoupled C NMR spectrum of 1-propanol (CH3CH2CH2OH) in H20 solvent. See text for details, (c) The NMR spectrum of 1-propanol (CH3CH2CH2OH) in H20 solvent. See text for details.

The proton-decoupled spectrum of 2-butanol consists of four signals corresponding to the four nonequivalent carbon atoms, as we saw in Figure 14.18. We can ehminate the isomers 2-methyl-1-propanol (Figure 14.19) and 2-methyl-2-propanol (Figure 14.20) as possible structures because the spectra of these compounds would show three and two signals, respectively. 

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