Nucleophilic Addition, Carbonyl Compound Mechanism - Organic Chem

In this video we want to describe the nucleophilic addition mechanism of carbonyl compounds, aldehydes and ketones.

Let's take a look at an example.

nucleophilic addition mechanism overall reaction of carbonyl compound

This reaction is done using trace NaOH or trace NaCN at 10 to 20 degree celsius.

1. Generation of Nucleophile

The first step is to generate the nucleophile.

If trace NaOH is used, there will be an acid-base reaction between NaOH and HCN to generate the nucleophile CN-.

If trace NaCN is used, it will be a simple dissociation to generate CN-.

The first step is the fast step.

nucleophilic addition mechanism step one generate nucleophile

2. Nucleophilic Attack

In the second step the nucleophile will attack carbonyl carbon to form a carbon-carbon bond.

The pi bond between carbon and oxygen will break and both electrons will be transferred to oxygen, forming an alkyoxide.

This second step is the slow step.

nucleophilic addition mechanism step two nucleophilic attack

3. Protonation and Regeneration of Catalyst

The alkyoxide oxygen will attack the reactant HCN and extract a proton or H+ from it, forming the product cyanohydrin.

CN- is regenerated in this process.

This final step occurs readily and is the fast step.

nucleophilic addition mechanism step three protonation and regenerate catalyst

For the detailed step-by-step discussion on how to draw this mechanism, check out this video!

Topic: Carbonyl Compounds, Organic Chemistry, A Level Chemistry, Singapore

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