Chapter 23-2

Chapter 23-2 - CHEM 262 Wei You Chapter 23. Amines (2) 11...

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11 CHEM 262 Wei You Chapter 23. Amines (2)
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Reaction with HNO2 22 HNO 2 H 2 O H 3 O + NO 2 - + p K a  = 3.37 + Nitrous acid, a weak acid, is most commonly prepared by treating NaNO2 with aqueous H2SO4 or HCl In its reactions with amines, nitrous acid participates in proton-transfer reactions is a source of the nitrosyl cation, NO+, a weak electrophile
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Formation of NO+ 33 NO+ is formed in the following way we study the reactions of HNO2 with 1°, 2°, and 3° aliphatic and aromatic amines H H N O + O H H + O H N O N O O H N O + + + + The nitrosyl cation (1) (2)
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Amines with HNO2 44 3° aliphatic amines, whether water-soluble or water-insoluble, are protonated to form water-soluble salts 3° aromatic amines: NO+ is a weak electrophile and, as such, participates in EAS 2° aliphatic and aromatic amines react with NO+ to give N - nitrosoamines Me 2 N 1. NaNO 2 , HCl,  0-5°C 2. NaOH, H 2 O N=O Me 2 N N,N -Dimethyl-4-nitrosoaniline N,N -Dimethylaniline N-H HNO 2 N-N=O H 2 O Piperidine N -Nitrosopiperidine + +
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Mechanism of 2° amine to N-nitrosamine 55 N H N O N H N=O H O H N N=O H O H H + + + + + • • • • • • • • • • • • (1) (2) 2° amine (a nucleophile) with the nitrosyl cation (an electrophile)
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Chapter 23-2 - CHEM 262 Wei You Chapter 23. Amines (2) 11...

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