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AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration...

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Page 1: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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AMINES

Page 2: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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AMINESAmines are organic nitrogen compounds, formed by replacing one or more hydrogen atoms of ammonia (NH3) with alkyi groups.

the amine nitrogen atom has a nonbonded electron pair, making it both a base and a nucleophile. As a result, amines react with electrophiles to form quaternary ammonium salts

Page 3: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Aromatic Amines

Nitrogen Heterocycles

Page 4: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Simple Amines and Alkaloids

Page 5: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Preparation of Amines

Three types of reactions are used to prepare an amine:[1] Nucleophilic substitution using nitrogen nucleophiles[2] Reduction of other nitrogen-containing functional groups [3] Reductive amination of aldehydes and ketones

Page 6: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Nucleophilic Substitution Routes to Amines

Page 7: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Examples

Page 8: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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The Gabriel Synthesis of 1o Amines

Avoid polyalkylation, the Gabriel synthesis consists of two steps and uses a nucleophile derived from phthalimide to synthesize 1o amines via nucleophilic substitution.

Page 9: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Problem

Page 10: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Reduction of Other Functional Groups that Contain Nitrogen

Page 11: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Reductive Amination of Aldehydesand Ketones

Page 12: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Page 13: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Reactions of Amines

Amines react as nucleophiles with electrophilic carbon atoms. Amines attack carbonyl groups to form products of nucleophilicaddition or substitution.

1. Reaction of 1o and 2o amines with aldehydes and ketones

Page 14: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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2. Reaction of NH3 and 1o and 2o amines with acid chlorides and anhydrides

Page 15: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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3. Reaction of amines with nitrous acid

Nitrous acid, HNO2, is a weak, unstable acid formed from NaNO2 and a strong acid like HCl

In the presence of acid, nitrous acid decomposes to +NO, the nitrosonium ion. This electrophile then goes on to react with the nucleophile nitrogen atom of amines to form diazonium salts (RN2

+Cl-) from 1o amines and N-nitrosamines (R2NN=O) from 2oamines.

Page 16: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Formation of a Diazonium Salt from a 1o Amine

Page 17: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Substitution Reactions of Aryl Diazonium Salts

Aryl diazonium salts react with a variety of reagents to form products in which Z (an atom or group of atoms) replaces N2, a very good leaving group. The mechanism of these reactions varies with the identity of Z, so we will concentrate on the products of the reactions, not the mechanisms.

Page 18: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Substitution Reactions of Aryl Diazonium Salts

HBF4 : fluoroboric acidH3PO2: hypophosphorus acid

Page 19: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Using Diazonium salts in Synthesis

Page 20: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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The Synthesis of 1,3,5-Tribromobenzene from Benzene

- Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).- Bromination of aniline yields the tribromo derivative in Step [3].- The NH2 group is removed by a two-step process: diazotization with NaNO2and HCI (Step [4]), followed by substitution of the diazonium ion by H with H3PO2.

Page 21: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Quiz

Solution

Page 22: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Coupling Reactions of Aryl Diazonium SaltsThe second general reaction of diazonium salts is coupling. When a diazonium salt is treated with an aromatic compound that contains a strong electron-donor group, the two ring join together to form an azo compound, a compound with a nitrogen-nitrogen double bond.

Example

Page 23: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Mechanism azo coupling

Because a diazonium salt is only weakly electrophilic, the reaction occurs only when the benzene ring has a strong electron-donor group Y, where Y = NH2, NHR, NR2, or OH. Although these groups activate both the orthoand para positions, para substitution occurs unless the para position already has another substituent present.

Page 24: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Quiz

Page 25: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Solution

Page 26: AMINES - Chemistry Silpakorn University Synthesis of 1,3,5-Tribromobenzene from Benzene - Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]).

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Natural Dyes


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