Chapter 21 amine

Chapter 21 amine - Chapter 21 Amines and Their Derivatives...

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Chapter 21. Amines and Their Derivatives I. INTRODUCTION Amines usually act as good nucleophiles, good bases, and sometimes week acids. The reason amines are reactive is because Nitrogen has low electronegativity (EN). Low EN means that Nitrogen does not hold-on very tight to its lone pair of electron, thus more willing to donate the electrons, acting as nucleophile or base. Reactivity of amines depends on substituents attached and bulkiness. Electron donating groups (EDG) increase the electron density of amine and therefore the amines become more reactive. Electron withdrawing groups (EWG) reduce the electron density of amine and thus the amine would become less reactive. NH 3 NH 2 N H N NH 4 -small -unhindered -small -unhindered -not hindered -2 EDG -high electron density -hindered -3 EDG - very high electron density -electron deficient -lone pair is not available FUNCTION: primary secondary tertiary quartenery NH 2 NH 2 N H O R -lone pair of electron on N is free -ethyl group is an EDG, thus increase the electron density of N primary amine aniline amide Example -lone pair on N is being donated toward the ring to form resonance -lone pair on N is being donated toward the carbonyl to form resonance NH 2 NH 2 Feature: N H O R N H O R Consequence: -primary amines have high electron density and thus more reactive as nucleophiles and bases -the N on aniline is losing its electron density as the result of resonance -N is less reactive as nucleophile or base compared to a primary amine -the N on amide is losing its electron density -amide N is NOT reactive as nucleophile or base The eletron density of the N determines its reactivity. Amines can act as good nucleophile and good base. Whether amines would act as nucleophile or base depends on another factor--STERIC HINDERANCE. -very good nucleophile because it is small -OK base -very good nucleophile because it is small -OK base -very good nucleophile due to high electron density -more reactive than primary amine -good base -very good base due to high electron density -poor nucleophile due to steric hiderance -a weak acid pKa = 9
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II. MAKING OF AMINES
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This note was uploaded on 01/21/2012 for the course ECON 2a taught by Professor Xi during the Spring '11 term at Cornell College.

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Chapter 21 amine - Chapter 21 Amines and Their Derivatives...

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