aromatic rings and amines

aromatic rings and amines - Aromatic Rings and Amines This...

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Aromatic Rings and Amines This guide to the lecture material and content of Aromatic Rings and Amines has been broken up into several broad categories which have then been arranged by page. This should NOT be used instead of lecture material, or relied solely upon for information, and I take no responsibility for any errors contained herein. 1. Contents and Nomenclature 2. Nitrogen Chemistry Azides, Nitriles, the Gabriel Synthesis Amines as protecting groups Mannich reaction and Hofmann re-arrangement 5. The Basicity of Nitrogen compounds 6. Aromatic Compounds Aromatic Halogenation Nitration Diazonium salts Friedel-Crafts 9. Direction of substituents on an already substituted benzenes Activating/Deactivating groups Resonance/Inductive stabilisation 11. Other aromatic reactions Benzyne, Diels Alder, Carbonyl chemistry, benzyl derivatives 13. Substituting benzenes – Examples Important Nomenclature before beginning H O alpha beta gamma H O 1 2 3 4 The left diagram shows the nomenclature that you should properly familiarise yourself with before reading this document. In the case of calling carbons alpha, beta or gamma, I will use their Greek letter counterparts; α, β, and γ- carbons.
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Nitrogen Chemistry Use of azides Azides can be used as typical nucleophiles, and displace bromide ions in a Sn 2 reaction. Br N 3 N 3 = N N N Ph Ph Ph N N N NH 2 H 2 / Pd LiAlH 4 Nitrile groups Nitrile groups can also be used to displace Bromide by the exact same reaction mechanisms. This is another good way of making amine groups while inserting a carbon as well. Br CN N DMSO LiAlH 4 NH 2 Gabriel Synthesis In the Gabriel synthesis a N-keto-amide can deprotonate quite easily to form a very stable anion. NH O O K 2 CO 3 mild base N O O Ph Br N O O Ph The stability of this anion is because the charge can be very easily delocalised onto three electronegative atoms, making this a good acidic species. N O O N O O O N O
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The addition of sodium hydroxide base to the N-keto-amide cleaves the bond between the nitrogen atom and the keto groups. N O O Ph NaOH CO 2 Na CO2Na + H 2 N Ph H + /H 2 O CO 2 H CO 2 H H 3 N Ph Water Soluble Organic Soluble Water Soluble Organic Soluble The useful thing about the Gabriel reaction is that all the products can be very easily separated due to their varying inherent solubility’s in solvents. Amines as protecting groups Amines can also be used as protecting groups in carbonyl alkylation. O N H N N This is useful to prevent aldehyde self-condensation. There is more information on this in previous notes. Mannich Mannich is another important reaction involving an amine. This is covered reasonably thoroughly in monofunctional carbonyl notes. However, there is another mechanism that is useful for reducing ketones to amines. Ph
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aromatic rings and amines - Aromatic Rings and Amines This...

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