18-Annulene shows two signals in its 1H NMR spectrum, one at 8.9 (12 H) and one at −1.8 (6...

18-Annulene shows two signals in its 1H NMR spectrum, one at 8.9 (12 H) and one at −1.8 (6 H) ppm. Using a similar argument to that offered for the chemical shift of benzene protons, explain why both shielded and deshielded values are observed for 18-annulene.