Question
Strecker Synthesis:
Step #1: The carbonyl oxygen is protonated, increasing the electrophilicity of the carbonyl carbon.
Step #2: Ammonia can attack the carbonyl carbon, forming an imine.
Step #3: ____.
Step #4: The nitrile nitrogen is protonated, increasing the electrophilicity of the nitrile carbon, then attacked by a water molecule multiple times to kick off ammonia and create carboxylic acid functionality.
Answer
Strecker Synthesis:
Step #1: The carbonyl oxygen is protonated, increasing the electrophilicity of the carbonyl carbon.
Step #2: Ammonia can attack the carbonyl carbon, forming an imine.
Step #3: The imine carbon is also susceptible to nucleophilic addition reactions; thus, the CN– anion from KCN attacks, forming a nitrile group (–C≡N), resulting in final product of aminonitrile.
Step #4: The nitrile nitrogen is protonated, increasing the electrophilicity of the nitrile carbon, then attacked by a water molecule multiple times to kick off ammonia and create carboxylic acid functionality.
Note ↑: The carbonyl carbon of an amide is sp2
hybridized and has trigonal planar geometry. A second
resonance structure can be drawn that delocalizes the nonbonded electron pair on the N atom.
Amides are more resonance stabilized than other acyl compounds, so the resonance structure
having the C=N makes a significant contribution to the hybrid.
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