The NMR results obtained using the B3PW91/aug-cc-pVTZ method in CHCl3 solvent are presented and compared with available experimental measurements in Table . This DFT functional (B3PW91) is considered the most accurate among several examined DFT functionals (B3PW91, PBEPBE, CAM-B3LYP, and M06-2x) combined with the aug-cc-pVTZ basis set, as it yields the smallest root-mean-square-deviation (RMSD) for carbon chemical shifts compared to measured values. This finding is consistent with our previous study . The calculated 13 C-NMR chemical shifts (δC) for NBD, NBN, and NBA in gas phase and CHCl3 solvent are provided in Expt [51] Expt [60] Expt [18] Expt [20] C1,C4 . The δC of the bridgehead carbons (C1 and C4) of PPL, however, are extremely shielded (δC (C1, C4) = 3.06 ppm). This can be attributed to several factors, including strain effects, shielding effects from adjacent atoms, and the absence of significant deshielding contributions from nearby functional groups. The bridge carbon atoms of PPL experience considerable strain due to their position at the junction of the cyclopropane rings, contributing to the observed small δC. Additionally, the presence of multiple bonds in the immediate vicinity of the bridge carbon atoms can shield them from the external magnetic field, resulting in a smaller chemical shift. Moreover, the bridge carbon atoms of PPL are surrounded by carbon and hydrogen atoms, which are relatively electron-neutral and thus do not induce significant deshielding effects. Finally, the cyclopropane rings in PPL can induce ring current effects on the bridge carbon atoms, further contributing to the extremely small δC of the bridge carbons (C1 and C4) of PPL. The 13 C-NMR spectrum serves as a valuable tool for characterizing the components of fuels, particularly in determining the degree of saturation, as SAF or efuel often comprises a mixture of hydrocarbons . For instance, the observed chemical shifts (δC) in the spectrum can distinguish between saturated and unsaturated components of the fuel. By comparing these shifts to known values for saturated and unsaturated hydrocarbons, one can infer the presence and relative proportions of these components in the fuel mixture. Such analysis is instrumental for quality control, assessing the composition and properties of aviation fuels, and monitoring changes in fuel composition due to processing or degradation .