Lidocaine part1

Lidocaine part1 - Experiment 4A 4B Preparation of Lidocaine...

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1 Experiment 4A & 4B: Preparation of Lidocaine This two-step synthesis involves the following conversion: 2,6-dimethylaniline α - chloro-2, 6-dimethylacetanilide Lidocaine. This synthetic scheme is shown in equation (1). Each step is discussed in more detail in each individual part of the lab along with experimental procedures. Overall Reaction Sequence: CH 3 CH 3 NH 2 + Cl O Cl N H CH 3 CH 3 O Cl N H CH 3 CH 3 O N 2, 6-dimethylaniline a-chloroacetyl chloride a-chloro-2,6-dimethylacetanilide diethylamine Lidocaine (1) (CH 3 CH 2 ) 2 NH
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2 Experiment 4A: Preparation of α -chloro-2, 6- dimethylacetanilide from 2,6-dimethylaniline . INTRODUCTION 2, 6-Dimethylaniline is converted to α -chloro-2, 6-dimethylacetanilide by allowing it to react with α -chloroacetyl chloride, as shown in equation (2). CH 3 CH 3 NH 2 + Cl O Cl N H CH 3 CH 3 O Cl 2, 6-dimethylaniline α -chloroacetyl chloride α -chloro-2, 6-dimethylacetanilide (2) CH 3 CO 2 H The nitrogen atom in 2, 6-dimethylaniline is a nucleophile because of the non-bonding pair of electrons on nitrogen. Nucleophilic substitution occurs selectively at the acyl carbon atom in α -chloroacetyl chloride because of the greater reactivity of nucleophiles toward acid chlorides compared to alkyl chlorides. The reasons for this selectivity are attributed to the differences in the electrophilicity of the two carbon atoms in α - chloroacetyl chloride. Electronically, the carbonyl carbon has two electron-withdrawing groups – the oxygen doubly bonded to it and the -Cl bonded to it. On the other hand, the carbon in –CH 2 Cl has only one electron-withdrawing group (-Cl). Besides electronics, steric factors also play a role in this selectivity. It is easier for the nucleophile to attack the carbon of the planar carbonyl group in the acid chloride than to attack the tetrahedral carbon in the –CH 2 Cl group. The mechanism for the substitution reaction that occurs between an amine and an acid chloride may be found in lecture textbooks and may be discussed by your instructor. This reaction is carried out in glacial (anhydrous) acetic acid as the solvent.
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This note was uploaded on 12/13/2010 for the course MATH 251 taught by Professor Unknown during the Spring '08 term at Simon Fraser.

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Lidocaine part1 - Experiment 4A 4B Preparation of Lidocaine...

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