- Information
- AI Chat
8A Exploring the Benzoin Condensation Catalyzed by Thiamine
Organic Chem Lab Ii (CHEM 373)
Eastern Washington University
Preview text
Exploring the Benzoin Condensation Catalyzed by Thiamine: Formation of a Carbon-Carbon Bond Benzoin, a compound with a wide range of applications in organic synthesis and pharmaceuticals, has been a subject of interest in the field of chemistry for many years. Its versatility stems from its ability to serve as a precursor for various compounds, including pharmaceuticals, fragrances, and dyes. Historically, benzoin has been used in traditional medicine as an antiseptic and a remedy for respiratory ailments. In the 19th century it was first isolated from the resin of certain trees and later synthesized in the laboratory. The purpose of this experiment is to synthesize benzoin via the thiamine-catalyzed benzoin condensation reaction, a classic method in organic chemistry. The synthesis of benzoin from thiamine hydrochloride and benzaldehyde provides an excellent opportunity to explore fundamental organic reactions. Additionally, this experiment aims to demonstrate the importance of purification techniques such as recrystallization in obtaining a pure product suitable for further analysis and use. By optimizing reaction conditions and purification methods, this aims to enhance the purity and yield of benzoin, thus contributing to the advancement of synthetic chemistry techniques. Thiamine hydrochloride (3 g, 11 mmol) was dissolved in a mixture of water (4 mL) and ethanol (30 mL, 95%). Sodium hydroxide solution (9 mL, 2 M) was added dropwise to the reaction mixture. After the addition of NaOH, the mixture became clear with a pale-yellow color remaining. Benzaldehyde (10 mL) was then added and stirred for at least 10 minutes. The reaction mixture was sealed with a septum and stored until the next lab period. On the following day, the reaction mixture was cooled in an ice bath. The crude product was isolated by vacuum filtration, yielding a mass of 7 g. The crude product was then recrystallized by dissolving it in ethanol (95%) and heating until fully dissolved. After cooling to room temperature, the purified product was collected by vacuum filtration. The
yield of the recrystallized product was found to be 7 g. The purified benzoin exhibited a pale-yellow color and a crystalline consistency. The infrared spectrum of the recrystallized benzoin showed characteristic peaks at 3406 cm^-1 (92%, hydroxyl groups), 1677 cm^-1 (86%, carbonyl groups). The melting point range of the product was observed to be 133°C to 135°C. Peaks observed at 1 ppm (0) and 1 ppm (0) indicate the presence of alkyl groups. A signal at 3 ppm (0) suggests protons adjacent to carbonyl groups. Peaks at 4 ppm (0) and 6 ppm (1) correspond to aromatic protons. Additionally, signals at 7 ppm (7) and 7 ppm (1) indicate aromatic protons. The peak at 8 ppm (2) may correspond to protons on aromatic carbon atoms. These NMR signals collectively provide evidence for the successful formation of benzoin. In this experiment, the purity of the benzoin product was primarily analyzed through its melting point range and infrared spectroscopy data. The observed melting point range of 133°C to 135°C, consistent with the literature value for benzoin, suggested that the product was likely pure. Additionally, the infrared spectrum of the recrystallized benzoin showed characteristic peaks corresponding to the expected functional groups, further confirming the purity of the product. However, the crude product obtained after the reaction appeared as a pale-yellow solid with a granular and somewhat powdery texture, indicating the presence of impurities and unreacted starting materials. Upon recrystallization, the product underwent purification, resulting in the formation of recrystallized benzoin. The recrystallized product exhibited a more defined crystalline structure with a finer texture compared to the crude product, appearing as a pale-yellow glitter solid with a more uniform appearance. While the experiment yielded a product with satisfactory purity and yield, the presence of impurities in the crude product suggests the possibility of side reactions or incomplete conversion of starting materials. Further, improving how the ingredients are mixed and cleaned up afterward could make the product even better.
8A Exploring the Benzoin Condensation Catalyzed by Thiamine
Course: Organic Chem Lab Ii (CHEM 373)
University: Eastern Washington University
