1. Aldol reactions (condensation of two aldehydes or ketones to yield a ẞ-hydroxy carbonyl) can go in reverse (B-hydroxy carbonyl to two aldehyde/ketones, a retro-aldol). Propose mechanisms for the following two transformations, using both intra-molecular aldol and a retro-aldol reactions. Be sure to follow the rules we have discussed for writing reaction mechanisms! H₂C. H&C. Na+ -OEt ethanol H₂C- H₂C. HO Na OEt ethanol

I H H3C NOC XT :0: MET H₂C base H3C The aldol reaction is a carbonyl condensation reaction between two carbonyl partners and involves a combination of nucleophilic addition and a-substitution steps. One partner is converted into an enolate ion nucleophile and adds to the electrophilic carbonyl group of the second partner. In the classic aldol reaction, the carbonyl partners are aldehydes or ketones, although aldehydes are more reactive. The product is a ß-hydroxy carbonyl compound. H OH q H3C H₂C H Under reaction conditions slightly more vigorous than those employed for the aldol reaction, the ß-hydroxyl group is eliminated in an E1cB dehydration to give an a,ß-unsaturated carbonyl compound. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions heat H H + H₂O

2 H3C H3C H C→XT OH H3C The aldol reaction is a carbonyl condensation reaction between two carbonyl partners and involves a combination of nucleophilic addition and a-substitution steps. One partner is converted into an enolate ion nucleophile and adds to the electrophilic carbonyl group of the second partner. In the classic aldol reaction, the carbonyl partners are aldehydes or ketones, although aldehydes are more reactive. The product is a ß-hydroxy carbonyl compound. base :0: OH H H Under reaction conditions slightly more vigorous than those employed for the aldol reaction, the ß-hydroxyl group is eliminated in an E1cB dehydration to give an a,ß-unsaturated carbonyl compound. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instruct ns H3C heat OH H3C :0: H + H₂O H

2 Moin H3C H H₂C C⇒x= base :0: OH Hori H3C H. The aldol reaction is a carbonyl condensation reaction between two carbonyl partners and involves a combination of nucleophilic addition and a-substitution steps. One partner is converted into an enolate ion nucleophile and adds to the electrophilic carbonyl group of the second partner. In the classic aldol reaction, the carbonyl partners are aldehydes or ketones, although aldehydes are more reactive. The product is a B-hydroxy carbonyl compound. Under reaction conditions slightly more vigorous than those employed for the aldol reaction, the ß-hydroxyl group is eliminated in an E1cB dehydration to give an a,ß-unsaturated carbonyl compound. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions H₂C Ἡ :0: heat H Home H3C + H₂O