How to decide order of mesomeric effect across the period?
Answers
Answer:
Explanation:
The mesomeric effect in chemistry is a property of substituents or functional groups in a chemical compound. It is defined as the polarity produced in the molecule by the interaction of two pi bonds or between a pi bond and lone pair of electrons present on an adjacent atom. The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structures and is symbolized by the letter M. The mesomeric effect is negative (–M) when the substituent is an electron-withdrawing group and the effect is positive (+M) when the substituent is an electron releasing group.
+M EFFECT ORDERS :
–O− > –NH2 > –NHR > –OR > –NHCOR > –OCOR > –Ph > –F > –Cl > –Br > –I
-M EFFECT ORDER :
–NO2 > –CN > --S(=O)2−OH > –CHO > –C=O > –COOCOR > –COOR > –COOH > –CONH2 > –COO−
The net electron flow from or to the substituent is determined also by the inductive effect. The mesomeric effect as a result of p-orbital overlap (resonance) has absolutely no effect on this inductive effect, as the inductive effect has purely to do with the electronegativity of the atoms and their topology in the molecule (which atoms are connected to which).
Answer:
The mesomeric effect is negative (–M) when the substituent is an electron-withdrawing group and the effect is positive (+M) when the substituent is an electron releasing group. The net electron flow from or to the substituent is determined also by the inductive effect.