Order of selectivity

Have you ever found the benzene rings attractive yet sophisticated?? Here are a few reactions with benzene, different other compounds when they have different types of groups attatched to it and their mechanism explained in a very easy way for you to grab easily.. Hope you find it much helpful for your preparation process….

Order of selectivity

• If an withdrawing group is attached to the Benzene ring, then electrophile will get substituted at the meta position
• If an donating group is attached to benzene ring, then electrophile will be substituted on ortho or para position depending on the reactant

Example

Due to Resonance of it withdraw from ortho & para position. Comparatively density is more on meta position.
attacks on meta position.

• If in the above, substitute is already present on one meta position, then substitution occur on remaining meta position.
  
  i.e. if

Haloform reaction

• This reaction is possible for aldehyde, ketone, alcohol & alkyl halide & is carried out in basic medium
• It is the diagnostic test of keto-methyl group
• This reaction is one of the best method for oxidation of ketone into carboxylic acid
• forms yellow ppt

Condensation reactions

• This is the most important part of aldehydes & ketones. Condensation means formation of new carbon-carbon bonds by forming some smaller products from original reactant
• Condensation reactions are examples of nucleophilic addition
• Reactions r.d.s (rate determining step) is the conversion of hybridized atom

Aldol condensation

It is possible for aldehydes of ketones having at least one - hydrogen.

Aldol is -hydroxyaldehyde or -hydroxyketone

Mechanism