The reaction below is called and electrophilic aromatic substitution reaction and occurs for all aromatic compounds such as benzene.  is a catalyst in this reaction to polarize the  to give  allowing for the presence of polarized  which is more reactive. Below is the mechanism for this reaction:

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Additon of an acid in the final step gives the final product.

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Addition of an acid in the final step gives the final product.

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Addition of an acid in the final step gives the final product.

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Addition of an acid in the final step gives the final product.

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Addition of an acid in the final step gives the final product.

Claisen condensation is a reaction between two molecules containing an ester functional group. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. The ion that is formed nucleophilicly bonds to a second ester molecule. As seen below, an ethoxide molecule expels. Addition of an acid in the final step gives the final product.

Alkylation is a reaction form an yield an alkyl compound. Similar to ketones and aldehydes, esters are weakly acidic because the alpha hydrogen to the carbonyl group can be deprotonated in the presence of a base. LDA is a base that converts these compounds to the enolate ion. The reaction is done in a aprotic solvent. This reaction yields an alkyl group in the alpha position of a ketone, ester or nitrile through nucleophilic substitution by reaction with an alkyl halide with and enolate ion.