318-24 - CH 318 N LECTURE 24 Textbook Assignment Chap 23...

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CH 318 N LECTURE 24 Textbook Assignment: Chap 23 Begin Homework (for credit): POW 12 posted Today’s Topics: AMINES Notice & Announcements: Organic Lecture Series 2 Amines Amines Epinephrine (adrenaline)
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Organic Lecture Series 3 Preparation Preparation • A summary of synthetic methods: – nucleophilic ring opening of epoxides by ammonia and amines (11.9B) – addition of nitrogen nucleophiles to aldehydes and ketones to form imines (Section 16.8) – reduction of imines to amines (16.8A) – reduction of amides by LiAlH 4 (18.10B) – reduction of nitriles to a 1° amine (18.10C) – nitration of arenes followed by reduction of the NO 2 group to 1° amines (22.1B) Organic Lecture Series 4 • Alkylation of ammonia and amines by S N 2 – unfortunately, such alkylations give mixtures of products through a series of proton transfer and nucleophilic substitution reactions CH 3 Br NH 3 3 NH 3 + - (CH 3 ) 2 2 + - 3 ) 3 + - 3 ) 4 N + - + ++ + + S N 2 Methylammonium bromide 3 3 3 3 + - Preparation Preparation These arise from N-polyalkylation
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Organic Lecture Series 5 Preparation via Azides Preparation via Azides Alkylation of azide ion, N 3 - - - ++ - Azide ion (a good nucleophile) An alkyl azide NN R N 3 - RN 3 : :: : Ph CH 2 Cl K + N 3 - 2 N 3 1. LiAlH 4 2. H 2 O 2 NH 2 Benzyl chloride Benzyl azide Benzylamine Organic Lecture Series 6 – alkylation of azide ion ArCO 3 H O 2. H 2 O N 3 OH 1. K + N 3 - LiAlH 4 H 2 O 2 Cyclohexen e trans- 2-Amino- cyclohexanol (racemic) 1,2-Epoxy- cyclohexane (chiral) 2-Azido- (racemic) Preparation via Preparation via Azides Azides Ar C O O OH (This is a peracid- It’s used for epoxide formation (11.8)
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Organic Lecture Series 7 • Nitrous acid, a weak acid, is most commonly prepared by treating NaNO 2 with aqueous H 2 SO 4 or HCl • In its reactions with amines, nitrous acid – participates in proton-transfer reactions – is a source of the nitrosyl cation, NO nitrosyl cation, NO + , a weak electrophile HNO 2 H 2 OH 3 O + NO 2 - + p K a = 3.37 + Reaction with HNO Reaction with HNO 2 2 (HONO) (HONO) Organic Lecture Series 8 NO NO + is formed in the following way: – Focus upon reactions of HNO 2 with 1°, 2°, and 3° aliphatic and aromatic amines H H + O H H + O HN O N OO H + + + + The nitrosyl cation (1) (2) Reaction with HNO Reaction with HNO 2 2 (HONO) (HONO)
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Organic Lecture Series 9 Amines with HONO Amines with HONO – 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 + + Organic Lecture Series 10 • Reaction of a 2° amine to give an N -nitrosamine – Step 1: reaction of the 2° amine (a nucleophile) with the nitrosyl cation (an electrophile) – Step 2: proton transfer N H NO N H N=O HO H N H H + + + + + •• (1) (2) 2 o Amines with HONO Amines with HONO
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Organic Lecture Series 11 RNH RNH 2 with HONO with HONO 1° aliphatic amines
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  • Spring '08
  • willson
  • pH, Nucleophilic substitution, Amine, Organic reaction, Organic Lecture Series, Diene Organic Lecture Series, Lecture Series Medicinal Chemistry

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318-24 - CH 318 N LECTURE 24 Textbook Assignment Chap 23...

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