Question

Write 4 differences between Nucleophilic substitution reaction and elimination reaction.​

Answer 1

Answer:

The obvious difference between substitution and elimination reactions is that substitution reactions replace one substituent with another while elimination reactions simply remove the substituent. ... The major difference between the groups is the number of steps the reaction takes place over.

Answer 2

Answer:

Nucleophilic substitution is when a nucleophile attacks an electrophilic site (i.e. a particularly electropositive site) and displaces a substituent in order to form a new molecule.

One example of such a reaction looks something like this (without consideration of SN1 vs. SN2, for simplicity):



We can see that NH3 displaces Br−, because NH3 is a strong lewis base (nucleophile), while Br− is a good leaving group.

We can conclude that nucleophilic substitution reactions will overall have had a leaving group leave from the substrate, due to the participation of a nucleophile.

Electrophilic addition is addition onto an electrophile without displacement.

One common electrophilic addition reaction is actually the halogenation of alkenes to generate vicinal dihalides. It's the dihalogen that acts as the electrophile.



Initially the Br2 is actually not polarized. But when it approaches the alkene, since bromine is more electronegative than carbon, it slightly draws electron density from carbon, which then is led to donate electrons into bromine's antibonding orbital.

That causes a London-Dispersion distortion in the electron cloud of Br2, generating an induced dipole which, along with bromine donating electrons back to the other carbon's antibonding orbital, facilitates the movement of electrons into the bonding orbital of the rear bromine and breaks the bond.

The bromonium intermediate is unstable, allowing Br− to backside-attack and generate the vicinal dihalide, giving the anti addition product.

For this, we can say that electrophilic addition reactions will overall add something onto a previously electron-rich molecule, but the net result does not involve something having left the original substrate by the time the reaction is over.