R effect corresponds to mesomeric effect. It is the phenomenon by which an aromatic ring gets activated at different corners of the ring.(Benzene).
Groups like OH, OR and NH2, NHR, NR2 etc. are found to show +R effects

-R effect is the phenomenon when a functional group participating in resonance induces relatively greater positive charge in the first and the third atom of the ring. Groups like COOH, CHO, NO2, CN and NO etc show -R effect
						

							
Dear student,
Please find the answer to your question below.
 
R effect corresponds to mesomeric effect. It is the phenomenon by which an aromatic ring gets activated at different corners of the ring.(Benzene).
Groups like OH, OR and NH2, NHR, NR2 etc. are found to show +R effects 
 
-R effect is the phenomenon when a functional group participating in resonance induces relatively greater positive charge in the first and the third atom of the ring.
Groups like COOH, CHO, NO2, CN and NO etc show –R effect
 
Thanks and regards,
Kushagra