Este documento trata sobre las propiedades y reacciones de fenoles y aminas. Describe la estructura, nomenclatura, usos comunes y propiedades ácido-base de estos compuestos orgánicos. También resume las principales reacciones químicas de fenoles como nitración, halogenación y oxidación, y de aminas como metilación y formación de amidas.
Los Nueve Principios del Desempeño de la Sostenibilidad
Fenoles y aminas
1. FENOLES y AMINAS Prof. Ulises Urzúa Prog. Biología Celular y Molecular ICBM – Facultad de Medicina, Universidad de Chile Química Orgánica TM Clases 9-10, 12 Ago 2009
45. GRACIAS ! Prof. Ulises Urzúa [email_address] 978-6877 Block E zócalo
Notas del editor
Bakelite ™
Here is the first step to convincing you that the pKa of water should not be 7: water is clearly a weaker acid than hydrogen sulfide, whose pKa is 7.04, or boric acid, 9.14, or hydrogen cyanide, 9.31 The real problem is why the pKa should not be 14.0 -- the same as pKw Here is the reason: Kw is defined as [H+]*[OH-], and this turns out to be 1.E-14. For any acid HA in water, though, Ka is defined as [H+]*[A-]/[HA] So if we think of water as an acid, Ka = [H+] * [OH-] / [H2O] = 1.0E-14 / [H2O] What do we do for [H2O]? Well, 1 g of water occupies 1 mL, near enough, which means that 18 gram of water = 1 mol of water occupies 18 mL. So we can fit 55.6 mol of pure water in 1.00 L. It is therefore fair to say that the "concentration" of water is 55.6 M, and so Ka = 1.8E-16 The log of 1.8E-16 to base 10 is -15.75, which is the pKa value quoted in your question.
Sustitución electrofílica en el anillo
Un tiol es análogo a un alcohol
Relationship of Structure and Basicity in Amines 1. Electron-releasing groups increase the availability of nitrogen's lone pair and, as a result, also increase the basicity of amines; alkyl amines are more basic than ammonia. 2. Electron-withdrawing groups decrease the availability of the non-bonding electron pair and decrease basicity; amides are much less basic than ammonia. 3. In aromatic amines, the non-bonding electron pair on nitrogen overlaps with the benzene pi-cloud by resonance; this decreases the availability of the lone pair and stabilizes the compound. As a result, aromatic amines are considerably less basic than aliphatic amines. Electron-donating groups on an aromatic amine increase availability of the non-bonding pair whereas electron-withdrawing groups decrease availability; as a result electron-donating groups on an aromatic ring increase basicity and electron-withdrawing groups decrease basicity. The effect of these groups is greatest at the ortho and para positions.