why functional group do not show metameric effect at meta position?

Dear Student,

Functional groups donot show mesomeric effect at meta position. This is because the delocalisation of electrons donot take place at meta position. This can be shown with the help of resonating structures:

As can be seen in the resonating structures, the negative charge is not delocalised at meta position, therefore mesomeric effect is not shown at meta position.

Regards,