Lab G: Reduction of Vanillin

Structure of vanillin + name?

What are the pharmacological applications of vanillin?

Anticancer, antidiabetic

What is reduction at carbon?

• Results in a decrease in # of C-Z bonds (Z = element more electronegative than carbon); usually C=O bonds.

OR

• Results in an increase in # of C-H bonds.

What are reducing agents?

Provide the equivalent of 2 H atoms

What are the 3 types of reduction reactions?

1) Molecular H2

2) Dissolving metal reductions

3) Hydride reduction

What are the properties of the molecular H2 reaction?

• Simplest reducing agent

• Reductions carried out in the presence of a metal catalyst

What are the properties of the dissolving metal reductions reaction?

• Using alkali metals (as a source of e^-1) and liquid NH3 (as a source of protons).

What are the properties of the hydride reaction?

• Uses NaBH4 or LiAlH4 (delivers a H- ion)

• Acidic workup (delivers an H+ ion)

What are hydride reducing agents?

• Most useful for reduction of Aldehydes and Ketones

• Contain a polar metal-hydrogen bond that serves as a source of the nucleophile hydride (H:-).

Give 2 examples of hydride reducing agents

Why is LiAlH4 a much stronger reducing agent than NaBH4?

Because the Al-H bond is more polar than the B-H bond.

What conditions must LiAlH4 be carried out in?

Under anhydrous reaction conditions - water reacts VIOLENTLY w/ this reagent. Water is added as a proton source after the reduction w/ LiAlH4 is complete.

What are the properties of NaBH4?

• Milder + selectively reduced aldehydes + ketones in presence of most other functional groups.

• Safer + easier to handle than LiAlH4.

What is the reduction of aldehydes + ketones?

• An addition reaction – H2 added across the pi-bond.

• Also a reduction reaction – Alcohol product has a fewer C-O bonds than the starting carbonyl compound

Draw the reaction scheme of reduction of aldehydes and ketones

What are the products whe the starting material is an aldehyde or ketone?

Aldehyde: 1° alcohol

Ketone: 2° alcohol

Draw the reduction of vanillin reaction scheme