Question

Examples of resonance which are not mesomeric

Answer 1

Answer:

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 2

Answer:

Resonance is known as delocalization of charge or lone pair in a conjugating system.

Let's understand what is a conjugating system ?

Any hydrocarbon having = - =/+/-/.. system or lone pair - + system is known as conjugating system.

Like CH2=CH-CH2(+) is a conjugating system because of = - + nature of the system.

OH-CH2(+) is also a conjugating system because of lone pair - (+) system.

Now, lets talk about resonance :

Say a system is given : CH2=CH-CH2(+)

Lets analyse the things present in the system, = Bond, - bond and (+) charge.