DL-Benzoin
[CAS# 579-44-2]

Identification

• Classification: Pharmaceutical intermediate >> Heterocyclic compound intermediate >> Pyrimidine compound >> Ketones
• Name: DL-Benzoin
• Synonyms: 2-Hydroxy-1,2-diphenylethan-1-one
• Molecular Formula: C₁₄H₁₂O₂
• Molecular Weight: 212.25
• CAS Registry Number: 579-44-2
• EC Number: 209-441-5
• FEMA: 2132
• SMILES: C1=CC=C(C=C1)C(C(=O)C2=CC=CC=C2)O

Properties

• Melting point: 134-136 ºC

Safety Data

• Hazard Statements: H412
• Precautionary Statements: P273-P501

Discovory and Applicatios

DL-Benzoin is an organic compound that belongs to the class of α-hydroxy ketones, characterized by the presence of both a hydroxyl (–OH) group and a ketone (C=O) group on adjacent carbon atoms. The “DL” designation indicates that it is a racemic mixture containing equal amounts of both enantiomers (D- and L- forms) of benzoin. Its molecular formula is C₁₄H₁₂O₂, and it appears as a crystalline solid with a pale yellow to off-white color.

The discovery of benzoin traces back to the early 19th century when it was first obtained from benzaldehyde through a reaction now known as the benzoin condensation. This reaction, catalyzed by cyanide or other nucleophilic catalysts, involves the coupling of two benzaldehyde molecules to form benzoin. The process was one of the earliest examples of carbon–carbon bond formation in organic synthesis and marked an important milestone in the development of synthetic organic chemistry.

DL-Benzoin is typically prepared by the benzoin condensation of benzaldehyde under catalytic conditions. The reaction proceeds via a nucleophilic attack of the catalyst on the carbonyl carbon of benzaldehyde, followed by coupling with a second benzaldehyde molecule and subsequent proton transfers. The product is a racemic mixture since the reaction does not favor the formation of a single enantiomer.

In terms of applications, DL-Benzoin serves as an important intermediate in organic synthesis. Its α-hydroxy ketone structure makes it a versatile building block for the preparation of various pharmaceuticals, fragrances, and fine chemicals. It can undergo oxidation to benzil, a diketone used in the synthesis of heterocyclic compounds, or reduction to benzyl alcohol derivatives.

Benzoin is also employed in asymmetric synthesis when chiral catalysts or resolving agents are used to obtain enantiomerically pure forms. These chiral variants have applications in the synthesis of biologically active molecules where stereochemistry is critical.

In the polymer and materials industries, benzoin derivatives are used as photoinitiators or photosensitizers due to their ability to generate free radicals upon exposure to ultraviolet light. This property is exploited in processes such as polymerization and photocuring.

From a practical standpoint, DL-Benzoin is a relatively stable compound under standard laboratory conditions but can be sensitive to prolonged exposure to light and air, which may lead to slow oxidation. It is soluble in common organic solvents such as ethanol, ether, and chloroform, facilitating its use in various synthetic protocols.

Handling DL-Benzoin requires standard laboratory precautions including the use of gloves and eye protection. While it is not classified as highly toxic, exposure to dust or vapors should be minimized.

Overall, DL-Benzoin holds an important place in organic chemistry as a classical compound with both historical significance and ongoing utility in synthesis. Its role as an intermediate, precursor, and functional material continues to support diverse applications in pharmaceuticals, materials science, and chemical research.

References

2005. Identification and Characterization of Novel Benzil (Diphenylethane-1,2-dione) Analogues as Inhibitors of Mammalian Carboxylesterases. Journal of Medicinal Chemistry, 48(7).
DOI: 10.1021/jm049011j

2012. Biochemical and structural characterization of recombinant short-chain NAD(H)-dependent dehydrogenase/reductase from Sulfolobus acidocaldarius highly enantioselective on diaryl diketone benzil. Applied Microbiology and Biotechnology, 97(8).
DOI: 10.1007/s00253-012-4273-z

2024. Benzoin-Kondensation. Namensreaktionen.
DOI: 10.1007/978-3-031-52850-7_11