In the unsubstituted ring

Sets a and b are not related to each other for set a the reactivity of a single position in ferrocene = 1.0, and for set b the reactivity of a single position in the unsubstituted ring was taken as 1.0 so that the values for each compound in set b are not strictly comparable with each other. 

A small overall deshielding ( 0.1 ppm) of protons in the unsubstituted ring has been observed for derivatives bearing an electron-withdrawing substituent at either C-l ° or C-3. ... 

Monosubstituted naphthalene derivatives are usually hydrogenated in the unsubstituted ring 67,107... 

The protons in the unsubstituted ring relax slowly because ring rotation is fast. In the substituted ring, protons with one neighbour relax more slowly than those with two neighbours. Adapted from Adam, MJ. and Hall, L.D. (1980). J. organomet. chem., 186,289-96. 

Naphthalene (49) reacts with sodium in liquid ammonia to form a red complex which is quenched by methanol to form the 1,4-dihydro derivative (51), and may therefore be assumed to be the dianion (50).- If alcohol is present in the reaction mixture, then the 1,4,5,8-tetrahydro derivative (52) is formed (Scheme 6). 1-Naphthyl derivatives are reduced in the unsubstituted ring, whereas there is a maiked preference for reduction of the substituted ring in 2-methyl- and 2-methoxy-substituted isomers. This preference is not as well defined for bulkier substituents, however, and is reversed in the case of 2-f-butylnaphthalene further details are in a 1970 review. Because of the facile isomerization of the 1,4-dihydro isomers to conjugated derivatives, overreduction occurs readily and ether groups are fairly readily hydrogenolyzed. It is therefore important to select the reaction conditions with care.- ... 

Figure 7. Isotropic shift vs. T 1 for uranocene and the ring protons in the unsubstituted ring of mono-t-butyl, 32, and mono-t-butoxycarbonyluranocene, 42...

Draw the resonance contributors for the carbocation intermediate in nitration of naphthalene at C-1 include only structures that retain benzenoid aromaticity in the unsubstituted ring. 

Nitro substitution, as in 1-nitronaphthalene, makes forcing conditions necessary, and addition takes place in the unsubstituted ring across the 5,8 positions. 

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