Benzocaine: Cocaine and New Melting Point
Experiment # 45: Benzocaine
Abstract
The local anesthetic, benzocaine, was synthesized via the esterification of p-aminobenzoic acid with ethanol. The percent yield of crude product was determined to be 21% and the melting point was recorded at 86.2°C ± 0.2°C, with a 6.3% error from 92°C, the literature melting point of pure benzocaine. The crude product was then recrystallized to improve the purity of benzocaine and 57.4% was recovered. The new melting point range was measured at 89.1°C ± 0.3°C, which has a 3.15% error. The infrared spectrum of the recrystallized product was measured to further verify that the synthesized product was benzocaine.
Introduction
The discovery of benzocaine as a local anesthetic came out of necessity to find a replacement for other anesthetic compounds with high toxicity levels such as cocaine and similar synthetic drugs. Cocaine has been used for its pain relief and stimulant effects for centuries, specifically by the Amerindian population in the Peruvian Andes, in the form of chewing the coca leaf (Erythroxylon coca) (Pavia et al, 283). The pure crystalline tropane alkaloid and active component of the coca leaves, cocaine, was isolated in 1862, and was used as an anesthetic in surgical and dental procedures in the 1880’s (Pavia et al, 284). However, it was soon realized that the use of cocaine was not safe because the lethal dose was very close to the treatment dose and because of the toxic effects on the central nervous system, including addiction (McMaster University). As a result, scientists began to make substitute synthetic compounds similar in structure to cocaine, which consists of an aromatic residue, an intermediate chain, and a basic tertiary amino group, shown in figure 1.
Figure 1: Structure of Cocaine (ChemWiki)
All of the synthetic drugs that derived from the structure of cocaine had similar functional groups including an aromatic ring at one end, which is typically an ester of an
Abstract
The local anesthetic, benzocaine, was synthesized via the esterification of p-aminobenzoic acid with ethanol. The percent yield of crude product was determined to be 21% and the melting point was recorded at 86.2°C ± 0.2°C, with a 6.3% error from 92°C, the literature melting point of pure benzocaine. The crude product was then recrystallized to improve the purity of benzocaine and 57.4% was recovered. The new melting point range was measured at 89.1°C ± 0.3°C, which has a 3.15% error. The infrared spectrum of the recrystallized product was measured to further verify that the synthesized product was benzocaine.
Introduction
The discovery of benzocaine as a local anesthetic came out of necessity to find a replacement for other anesthetic compounds with high toxicity levels such as cocaine and similar synthetic drugs. Cocaine has been used for its pain relief and stimulant effects for centuries, specifically by the Amerindian population in the Peruvian Andes, in the form of chewing the coca leaf (Erythroxylon coca) (Pavia et al, 283). The pure crystalline tropane alkaloid and active component of the coca leaves, cocaine, was isolated in 1862, and was used as an anesthetic in surgical and dental procedures in the 1880’s (Pavia et al, 284). However, it was soon realized that the use of cocaine was not safe because the lethal dose was very close to the treatment dose and because of the toxic effects on the central nervous system, including addiction (McMaster University). As a result, scientists began to make substitute synthetic compounds similar in structure to cocaine, which consists of an aromatic residue, an intermediate chain, and a basic tertiary amino group, shown in figure 1.
Figure 1: Structure of Cocaine (ChemWiki)
All of the synthetic drugs that derived from the structure of cocaine had similar functional groups including an aromatic ring at one end, which is typically an ester of an
References: Experiment 9. Reactions of Carboxylic Acids & Their Derivatives. McMaster University - Chem2O06 Lab Manual. 28 September 2008. Available from http://www.chemistry.mcmaster.ca/~chem2o6/labmanual/expt9/2o6exp9.html Fischer esterification mechanism. Organic Chemistry Help. 28 September 2008. Available from http://www.chemhelper.com/fischester.html It07: Benzocaine. Chemistry Department Wiki, Imperial College London. Modified 7 December 2007. Accessed 28 September 2008. Available from https://www.ch.ic.ac.uk/wiki/index.php/It07:Benzocaine McMurry, John. Organic Chemistry. California: Thomson – Brooks/Cole. 2008. Pavia, Donald L., Gary M. Lampman, George S. Kritz, and Randal G. Engel. Essay: Local Anesthetics. Organic Chemistry Lab Manual. Ed. M Baird, M Staudt, and M Stranz. Mason, OH: Thomson Brooks/Cole. 2007. 283-286. Pavia, Donald L., Gary M. Lampman, George S. Kritz, and Randal G. Engel. Experiment 45: Benzocaine. Organic Chemistry Lab Manual. Ed. M Baird, M Staudt, and M Stranz. Mason, OH: Thomson Brooks/Cole. 2007. 287-289.