Which of the following represents + E effect ?
Which of the following represents + E effect ?
The correct option is A
It is a temporary delocalisation of π-electron in compounds containing multiple covalent bonds.
e.g., (C=C), (C=O), C≡ N, etc.
It takes place only when a reagent is added and vanishes when the attacking reagent is removed.
It is represented by a curved arrow(↷).
+E effect is represented when→es of the π-bonds are transferred to that atom to which the reagent gets finally attached.
The reactions of alkenes and alkynes mostly occur by +E mechanism and are called electrophilic addition (EA) reactions.
-E effect is represented when→es of π-bonds are transferred to electronegative atoms (O,N,S) joined by multiple bonds and the reagent gets finally attached opposite to that atom where the →e has been transferred.
The reactions of aldehydes and ketones mostly occur by -E mechanism and are called nucleophilic addition (N/A) reactions.
We can see that,
In reaction (a), π bond is shifting to CH2 and H gets attached to it.
Therefore, it is +E effect.
Whereas, in (b), it's opposite.
Therefore (b) is -E effect.
It is a temporary delocalisation of π-electron in compounds containing multiple covalent bonds.
e.g., (C=C), (C=O), C≡ N, etc.
It takes place only when a reagent is added and vanishes when the attacking reagent is removed.
It is represented by a curved arrow(↷).
+E effect is represented when→es of the π-bonds are transferred to that atom to which the reagent gets finally attached.
The reactions of alkenes and alkynes mostly occur by +E mechanism and are called electrophilic addition (EA) reactions.
-E effect is represented when→es of π-bonds are transferred to electronegative atoms (O,N,S) joined by multiple bonds and the reagent gets finally attached opposite to that atom where the →e has been transferred.
The reactions of aldehydes and ketones mostly occur by -E mechanism and are called nucleophilic addition (N/A) reactions.
We can see that,
In reaction (a), π bond is shifting to CH2 and H gets attached to it.
Therefore, it is +E effect.
Whereas, in (b), it's opposite.
Therefore (b) is -E effect.
