Identification of methylnaphthalenes by PMR: some useful rules

peri Interaction in Naphthalene Derivatives

“…In 2-methoxy-5-methyl-5,6,7,8-tetrahydronaphthalene, H4 proton absorption occurs at r 2.88, thus undergoing a deshielding of 0.16 by the adjoining methyl substituent (436). The aromatic and aliphatic proton spectra have been examined for many dimethylnaphthalenes (397, 435). Generally, the magnetic shielding of the proton (both a and ß) increases in the dimethyl derivatives compared to naphthalene.…”

“…From another investigation (435) on polymethyl-(and other alkyl-) naphthalenes, the following generalizations are suggested: (a) an -methyl group is deshielded more than a ß-methyl group; (b) an alkyl group ortho to methyl causes a shielding of 4 cps, with meta orientation it is about 2 cps, and with peri orientation it is at a maximum (12 cps).…”

The skraup syntheses and NMR spectra of some methylnaphthyridines

“…Since the NMR spectra of a rather large number of mono-and dimethyl derivatives of aza-, and of diazanaphthalenes a r e now available, it appeared reasonable to attempt to correlate the chemical shifts of the methyl protons of the different compounds. This became especially attractive in view of the correlation of the chemical shifts of the methyl protons in numerous mono-and dimethylnaphthalenes which had been previously described (5). If we choose the chemical shift of the methyl group protons of 2-methylnaphthalene ( 6 ) a s the reference protons, the difference between the chemical shift of the 2-methyl protons of this compound and the corresponding protons in 2-methylquinoline can be ascribed a s being due to the anisotropic contribution of the heteroatom versus the effect due to an sp2 carbon atom.…”