Benzocaine Lab Report PDF

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Benzocaine Lab Report...

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Experiment 6: Synthesis of Benzocaine October 15, 2019 TA: Amanda Chown CHEM 2081-001

Introduction In the late 1800s, cocaine was commonly used as an anesthetic in surgery and dentistry, but the ill effects of the drug led chemists to synthesize a less toxic drug to use as an anesthetic. Studies indicated that a successful analog should be a derivative of an aromatic acid, with the carbonyl group separated from a tertiary amine by a chain two to four atoms in length. As a result, two analogs were synthesized from cocaine: Benzocaine and Novocaine.4 Benzocaine and Novocaine are drugs that are just as effective of an anesthetic as cocaine but are significantly lower in toxicity. Benzocaine lacks the tertiary amine component; therefore, it is less active as an injectable drug. Today, benzocaine is extensively used as a topical pain reliever, such as Orajel, which is used to reduce pain caused by teething, cold sores, canker sores, and toothaches.4

Conclusion In this experiment, benzocaine was synthesized by reacting 4-Aminobenzoic acid with ethanol (CH3CH2OH) and sulfuric acid (H2SO4).1 The reaction proceeded as expected with little to no error. The experiment was expected to yield 0.149 g of benzocaine. The actual yield was 0.129 g leading to a percent yield of 87%. While transferring the product from the long-neck round-bottom flask to the watch glass, a small amount of the solid product remained in the flask because it was not easily transferrable out of the flask to the watch glass. This is a possible contributing factor leading to a less than perfect percent yield. A way to improve this experiment would to ensure that all of the product is transferred to the watch glass. If this would have happened, then the percent yield would have likely been closer to 100%. A future research experiment based on this data and conclusion would be instead of using ethanol as a means of synthesizing benzocaine, methanol could be used instead. Considering that methanol has one less

carbon atom and less hydrogen atoms, this could allow the reaction to take place in half the amount of time than when ethanol was used. Instead of waiting an hour for the reaction to take place, just wait 30 minutes. Even though the ethanol in this experiment was successful and produced a high percent yield, it would be interesting to see if methanol produced the same results with it having less carbon and hydrogen atoms present in the molecule. Based on the structures of cocaine, novocaine, and benzocaine, it is expected that there would be a difference in melting points between the three. Cocaine is the largest molecule and therefore has the higher melting point of 98°C due to the larger surface area.3 Benzocaine has the second highest melting point at 92°C because it is a tightly packed molecule. Novocaine has the smallest melting point at 61°C because it is a longer molecule that is not as compressed as the other two molecules.2

Calculations 0.12𝑔&𝐶( 𝐻( 𝑁𝑂, ×

1&𝑚𝑜𝑙&𝐶( 𝐻( 𝑁𝑂, 1&𝑚𝑜𝑙 &𝐶4 𝐻55 𝑁𝑂, & = 0.0009&𝑚𝑜𝑙&𝐶4 𝐻55 𝑁𝑂, & × 1&𝑚𝑜𝑙 &𝐶( 𝐻( 𝑁𝑂, 137.14𝑔&

0.0009&𝑚𝑜𝑙 &𝐶4 𝐻55 𝑁𝑂, ×

165.19𝑔&𝐶4 𝐻55 𝑁𝑂, = 0.149𝑔&𝐶4 𝐻55 𝑁𝑂, & 1&𝑚𝑜𝑙

Theoretical Yield: 0.149 g 𝐶4 𝐻55 𝑁𝑂, (benzocaine) Actual Yield: 0.129 g 𝐶4 𝐻55 𝑁𝑂,

𝑃𝑒𝑟𝑐𝑒𝑛𝑡&𝑌𝑖𝑒𝑙𝑑 =

=

𝐴𝑐𝑡𝑢𝑎𝑙&𝑌𝑖𝑒𝑙𝑑& × &100% 𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙&𝑌𝑖𝑒𝑙𝑑&

0.129&g&𝐶4 𝐻55 𝑁𝑂, && × &100% &0.149&g&𝐶4 𝐻55 𝑁𝑂, 𝑃𝑒𝑟𝑐𝑒𝑛𝑡&𝑌𝑖𝑒𝑙𝑑 = 87%

Mechanism

Figure 1: Reaction mechanism for the synthesis of benzocaine from 4-Aminobenzoic acid with ethanol (CH3CH2OH) and sulfuric acid (H2SO4).

Figure 2 (above): The structures of the analogs derived from cocaine.

Table 1 (below): The IUPAC name and chemical formulas of the analogs derived from cocaine. Cocaine

Novocaine

Benzocaine

IUPAC Name:

IUPAC Name:

IUPAC Name:

methyl (1R,2R,3S,5S)-3benzoyloxy-8-methyl-8azabicyclo[3.2.1]octane-2carboxylate

2-(diethylamino)ethyl 4aminobenzoate

ethyl 4-aminobenzoate

Chemical Formula: C7H21NO4

Chemical Formula: C9H11NO2 Chemical Formula: C13H20N2O2

References

1. Morvant, Mark C, et al. CHEM 2081 Organic Chemistry II Laboratory Manual. HaydenMcNeil, LLC, 2019. 2. Gillespie, Claire. “What Factors Affect Melting Point?” Sciencing, 2 Mar. 2019, sciencing.com/factors-affect-melting-point-8690403.html. 3. “PubChem.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine, pubchem.ncbi.nlm.nih.gov/. 4. “Orajel (Benzocaine Topical) - Side Effects, Dosage, Interactions - Drugs.” EverydayHealth.com, 18 Jan. 2016, www.everydayhealth.com/drugs/orajel....