Lab 5

Taniya Naznin

Lab Partners: Cursel Hazel, Jonathon Keimal, Zachary Cook

TA: Garrett Craft

Experiment 5: Synthesis of Acetylsalicylic Acid (Aspirin)

Introduction

Acetylsalicylic acid is often known as aspirin used to reduce fevers and as a pain killer (“Aspirin Synthesis”). This experiment will allow for the synthesis of aspirin to occur from salicylic acid and acetic anhydride in the presence of phosphoric acid. The experimental aspirin will then be compared to aspirin that’s normally sold in stores. In this reaction, an alcohol is reacting with an anhydride to produce an ester in the presence of an acid (Weldegirma, 2015). The salicylic acid acts as the alcohol and reacts with the excess acetic anhydride and is then quenched by adding water (“Aspirin Synthesis”). Since aspirin is not very soluble in water, the aspirin will precipitate in it while the acetic acid is easily separated from the product due to its solubility in water (“Aspirin Synthesis”). Another method an ester can be prepared is by Fischer esterification (Weldegirma, 2015). A Fischer esterification occurs when a carboxylic acid is reacted with an alcohol in the presence of a catalyst (Weldegirma, 2015). In the Fischer esterification, a carboxylic acid is protonated and then attacked by the nucleophile, the alcohol, to cause a tetrahedral intermediate with two equivalent hydroxyl groups (“Fischer Esterification Fischer-Speier Esterification”). A proton shift then causes one of these hydroxyl groups to be eliminated leaving water and the ester as the final products (“Fischer Esterification Fischer-Speier Esterification”).

Mechanism

Side Reaction

Experimental

Table of Chemicals

Chemicals | Salicylic Acid | Acetic Anhydride | Phosphoric Acid | Acetylsalicylic Acid |

Formula | C7H6O3 | C4H6O3 | H3PO4 | C9H8O4 |

Melting point (°C) | 158.6 °C | 139.8°C | 42.35 °C | 136.0 °C |

Boiling point (°C) | 211.0 °C | 139.8°C | 158.0 °C | 140.0 °C |

Density | 1.443 g/cm3 | 1.082 g/cm3 |...