Q10 / 180 · KCET 2013 · Chemistry

Mesomeric effect involves

  • Correct answer
    A
    delocalisation of $\pi$-electrons
  • B
    delocalisation of $\sigma$-electrons
  • C
    partial displacement of electrons
  • D
    delocalisation of $\pi$ and $\sigma$-electrons

Solution

Resonance or mesomeric effect is defined as, the polarity produced in the molecule by the interaction of two $\pi$-bonds or between a $\pi$-bond and a lone pair of electrons present on an adjacent atom. There are two types of mesomeric effect. $+M$ effect is observed when direction of electron displacement is away from an atom or substituent group attached to the conjugated system e.g., - halogen, $-\mathrm{OH},-\mathrm{NH}_{2}$ etc. On the other hand, - M effect is observed when the transfer of electrons is towards the atom or substituent group attached to the conjugted systems, e.g., $-\mathrm{NO}_{2},-\mathrm{COOH}$ etc.

Hence, the correct answer is option: 'A'.

Relevant Questions