Introduction:
In organic chemistry, the I (inductive) and -I (negative inductive) effects refer to the electron-withdrawing or electron-donating nature of substituents in a molecule. These effects can be observed in phenols, which are aromatic compounds containing a hydroxyl group (-OH) attached to a benzene ring. The I and -I effects in phenols are influenced by the distance between the substituent and the hydroxyl group.

Explanation of I and -I effects:
The I effect occurs when a substituent donates or withdraws electron density through the sigma bond framework of a molecule. It is determined by the electronegativity difference between the substituent and the atom to which it is attached. A more electronegative substituent (e.g., halogens) exhibits a -I effect by withdrawing electron density from the aromatic ring.

Phenols can have substituents at different positions on the benzene ring, such as ortho (1,2), meta (1,3), or para (1,4) positions. The position of the substituent affects the strength and distance of the I and -I effects.

Distance and the -I effect in phenols:
The -I effect in phenols increases with an increase in distance between the substituent and the hydroxyl group. This can be explained by considering the electron delocalization in the aromatic ring.

When a substituent is present at the ortho position, it is closer to the hydroxyl group compared to the meta or para positions. As a result, the substituent's -I effect is stronger due to the shorter distance for electron withdrawal. The electron density is decreased on the aromatic ring, making it less reactive.

On the other hand, when the substituent is located at the meta or para positions, the distance between the substituent and the hydroxyl group is greater. Consequently, the -I effect is weaker due to the longer distance for electron withdrawal. The electron density on the aromatic ring is relatively higher, making it more reactive.

Effect on acidity:
The -I effect in phenols also affects their acidity. The stronger the -I effect, the more stable the resulting phenoxide ion, and therefore, the more acidic the phenol. Ortho-substituted phenols, with the strongest -I effect, are the most acidic among the three positions.

Summary:
In phenols, the -I effect increases with an increase in distance between the substituent and the hydroxyl group. The ortho position exhibits the strongest -I effect due to the shorter distance for electron withdrawal, while the meta and para positions have weaker -I effects because of the longer distances. This phenomenon influences the reactivity and acidity of phenols, making ortho-substituted phenols the most reactive and acidic among the three positions.