Polycyclic aromatic compounds chemical shift

The origin of equations 1 and 2 was explained in more detail in (6). The calibration of the bond polarization parameters for, 3C chemical shift tensors for C(sp3/sp2)-C, C(sp3/sp2)-H, C(sp3/sp2)-0, and C(sp3)-N o-bonds as well as C(sp2)-C and C(sp2)-0 71-bonds was described in detail in (5). Structural data and tensorial single crystal, 3C NMR data of 20 crystalline substances including sugars, polycyclic aromatic compounds, and amino acids were used in this calculation. 

Chemical Shifts of Selected Heterocyclic and Polycyclic Aromatic Compounds... 

M.H. Sherwood, J.C. FaceDi, D.W. Alderman, D.M. Grant, Carbon-13 chemical shift tensors in polycyclic aromatic compounds. 2. Single-crystal study of naphthalene, J. Am. Chem. Soc. 113 (1991) 750. 

As was true for the hydrogens attached to heteroaromatic rings and polycyclic aromatic hydrocarbons (Section 6.5), the carbons of such rings also appear in the aromatic region. Some examples are given below,1 and these can be used as base values when calculating chemical shifts for substituted derivatives of these compounds ... 

Aromatic compounds are defined as cyclic or polycyclic systems which sustain a diamagnetic ring current and consequently exhibit a total diatropic lowfield 1H NMR chemical shift relative to that of vinylic protons. Paramagnetic ring current is expected and was shown to be induced in antiaromatic species and to result in a total highfield H NMR band displacement, while non aromatic compounds give rise to characteristic vinylic XH patterns. 

The sidebands in C solid-state NMR spectra of 13 polycyclic aromatic hydrocarbon model compounds associated with kerogen structure were suppressed with C CP MAS TOSS NMR. The chemical shift values of these model compounds were obtained and were subsequently used to determine the chemical shifts of aliphatic and aromatic carbons in a series of kerogens via C CP MAS TOSS NMR. Dipolar dephasing (DD) was used to obtain the spectra of nonprotonated carbon present. ... 

---