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Experiment III-143B-SP 09

Experiment III-143B-SP 09 - Experiment III The Synthesis of...

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Experiment III: The Synthesis of Lidocaine Synthesis Type : Multiple-step; Linear Synthetic Transformations Involved : Reduction; Addition-Elimination (amide bond formation); Substitution (S N 2) Laboratory Techniques Involved : Filtration (Chapter 3, p.25-6), Extraction (Chapter 4), Evaporation of Solvent using a Rotovap (Chapter 4, p.39-40 and document on web site), Column Chromatography (Chapter 7), Crystallization (page 28), Recrystallization (Chapter 3, TLC (Chapter 8), Melting Point Determination (Chapter 2), IR Spectroscopy (Chapter 11), NMR Spectroscopy (Chapter 13) 1) Introduction Lidocaine ( III-05 ) is a long acting membrane stabilizing agent against ventricular arrhythmia. The substance was originally used as a mild local anesthetic with very few side effects. Lidocaine was first synthesized and patented by a Swedish pharmaceutical company (Astra) in 1948. Lidocaine sometimes goes under other names such as Lidothesin or Xylocain. It can be found today in many over-the-counter topical pain relievers (read the labels next time you're at the drug store!) HN NEt 2 O H 3 C CH 3 III-05 2) Synthetic Strategy The amide bond in lidocaine can be established taking the advantage of the free amine group of the aniline III-02 and a suitable carbonyl compound ( III-03 ) attached to good leaving groups (Cl). A free amine is considered a very good nucleophile not only toward acyl carbons, but also to sp 3 -hybridized carbons such as alkyl halides. Diethyl amine is the other amine used in the synthetic approach. The reaction conditions, in the case of the reaction between amine III-02 and acyl chloride III-03 , need some caution. Actually, it is relatively easy to distinguish between the two Cl-groups attached to III-03 in the reaction toward an amine if one considers the relative rate of the nucleophilic attack on different hybridized carbons. Finally, the aniline compound III-02 can be obtained from a reduction of the corresponding nitro compound III-01 .
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NO 2 H 3 C CH 3 1) SnCl 2 - H 2 O HN NEt 2 O H 3 C CH 3 HNEt 2 HOAc NH 2 H 3 C CH 3 HN Cl O H 3 C CH 3 Cl Cl O III-05 III-01 III-02 III-04 III-03 2) KOH 3) Pre-lab preparation Before performing this experiment, make sure that lab notebook is prepared accordingly. Draw the reaction scheme and make as many calculations as possible. Draw only one step (reaction) at a time. That is, draw the first step of the reaction and then record your laboratory results. When this is complete, draw your second reaction beginning on a new page, etc. You should review the chapters of your text relating to the "Laboratory Techniques Involved" as listed at the beginning of this experiment. You will need to develop TLC solvent conditions for each step. The final product will require purification via column chromatography so be sure to review the methods and techniques involved in this procedure. Be sure to include safety hazards about chemicals that you will be using.
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Experiment III-143B-SP 09 - Experiment III The Synthesis of...

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