Naphthalenes substituent increments

Substituent increments are obtained as usual by subtracting the reference shifts of naphthalene (C-1,4,5,8 127.7 C-2,3,6,7 125.6 C-9,10 133.3 ppm) from the individual data of C-l to C-10 in the substituted derivatives given in Table 4.55. It turns out that comparable Zx, Zmthn, Zmrta, and Zpara increments in naphthalene and benzene differ substantially in magnitude, as exemplified in Table 4.56. In 1-substituted naphthalenes, C-9 increments are attenuated in favor of C-2 relative to comparable ortho effects known from benzene C-3 and C-1 in 2-substituted naphthalenes behave correspondingly (Table 4.56). This can be explained by the cannonical formulae c, which do not contribute so much to the actual molecular state due to disrupted % electron sextets. Full inter-... 

Carbon-13 shifts of multisubstituted naphthalenes can be assigned by addition of substituent increments similar to eq. (4.16), provided no intramolecular interactions between substituents take place. This applies for 1,4-, 1,5-, 2,6-, and 2,7-disubstituted deriv-... 

Most of the substituent increments presented in Table 4.82 can be derived from 3C shifts of benzenoid carbons in monosubstituted benzenes as listed in Table 4.53. Additional substituent increments are available for fused aromatic rings such as naphthalene and... 

Table 4.56. Comparison of Methoxy- and Cyano Substituent Effects on Naphthalene and Benzene Carbon-13 Shifts (Zf in ppm). Benzoid Shift Increments are Printed in Italic Type.

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