When inductive and electromeric effects operate in opposite directions, the electromeric effect predominates.

Inductive Effect:
The inductive effect is a permanent effect that arises due to the polarization of sigma bonds in a molecule. It occurs when electronegative atoms or groups pull electron density towards themselves, creating a partial positive charge on the adjacent atom and a partial negative charge on the atom further away. This effect is transmitted through sigma bonds and decreases with distance.

Electromeric Effect:
The electromeric effect is a temporary effect that occurs due to the movement of electrons in a pi bond or a lone pair of electrons. It involves the shifting of electrons within a molecule or a functional group. When a pi bond or a lone pair of electrons is shifted to a neighboring atom or group, it leads to the formation of a resonance structure.

When inductive and electromeric effects operate in opposite directions, the electromeric effect predominates. This means that the temporary shifting of electrons in a molecule or functional group is more significant than the permanent polarization of sigma bonds.

Explanation:
The inductive effect is a constant effect that operates through sigma bonds and decreases with distance. It primarily depends on the electronegativity of the atoms involved. If the inductive effect operates in one direction, pulling electron density towards a particular atom or group, and the electromeric effect operates in the opposite direction, shifting electrons away from that atom or group, the electromeric effect will predominate.

The electromeric effect involves the movement of electrons, leading to the formation of resonance structures. This effect is temporary and can occur within a molecule or a functional group. When the electromeric effect operates in the opposite direction to the inductive effect, it can override the inductive effect and become the dominant factor in determining the electron distribution within the molecule.

In summary, when the inductive and electromeric effects operate in opposite directions, the electromeric effect predominates due to its ability to shift electrons and form resonance structures.