What are the uses of o-Phthalaldehyde in the chemical industry?

o-Phthalaldehyde (OPA) is one of the isomers of phthalaldehyde. It has been widely used as a powerful disinfectant due to its inherent antimicrobial properties. OPA is able to form fluorescent products with primary amines, making it useful for the detection and estimation of various biogenic amines, peptides, and proteins in body fluids. In addition, the conjugation of thiols and amines with OPA produces more sensitive fluorescent compounds, greatly improving the sensitivity and specificity of OPA-based analytical techniques.

Organic Synthesis

o-Phthalaldehyde, as an oxidant, can convert aromatic methyl ketones into esters and carboxylic acids in two steps. In the first step, o-phthalaldehyde oxidizes the methyl group to 1-indanone, which acts as a leaving group in the subsequent regioselective retro-Claisen condensation reaction to form esters and carboxylic acids.

Fluorescence Analysis

O-phthalaldehyde and its derivatives have been shown to react chemoselectively with primary amine groups on peptides, proteins, and proteomes under physiological conditions to form fluorescent isoindole derivatives in the presence of primary amines and free thiol moieties. A direct paper-based fluorescence analytical method was constructed with this substance for the quantitative determination of glutathione (GSH) molecules in nutritional supplements. It is based on the fluorescence emission generated by the direct and selective chemical reaction of GSH molecules with the derivatization reagent OPA under acidic conditions at room temperature. After irradiation with a 365 nm lamp, the fluorescence intensity emitted from the surface of the analytical paper device is proportional to the GSH concentration and can be measured using a smartphone as a detector. The method has good ease of operation, chemical stability and precision ranging from 3.1% (intraday) to 7.3% (interday). Finally, the method was successfully applied to three different dietary supplement samples.

Disinfectant and Tanning Agent

OPA is used as a disinfectant and tanning agent in the leather industry. It can be used to disinfect endoscopic instruments, thermometers, rubber and plastic equipment that cannot be sterilized by heating systems. OPA is an advanced disinfectant approved by the FDA in October 1999. It contains at least 0.55% 1,2-phenylenedialdehyde, or OPA, and has replaced glutaraldehyde as the most commonly used high-level disinfectant "aldehyde" in the United States. OPA solution is a clear, light blue liquid with a pH of 7.5. OPA is also used for hospital disinfection, it is nonirritating to mucous membranes and has an almost unnoticeable odor. It is more active than glutaraldehyde and can achieve high-level disinfection after a contact time of 12 minutes at 20°C or higher. However, it stains tissues and mucous membranes gray and may cause irritation in eye contact. Therefore, protective equipment must be worn when handling the solution, and items must be thoroughly rinsed off after handling.

References:

[1] ARUNAVA MISRA; Mohabul A M; Sudipta Mondal. O-Phthalaldehyde: A Versatile Chemical with its Roles and Future Perspectives[J]. Asian Journal of Organic Chemistry, 2024, 13 12. DOI:10.1002/ajoc.202400383.

[2] RAJENDRA PRASAD. Conversion of aromatic methyl ketones to esters and carboxylic acids using <i>o</i>-phthalaldehyde as an oxidant.[J]. Organic Biomolecular Chemistry, 2024. DOI:10.1039/d4ob01933d.

[3] MARIA TARARA; George Z T; Paraskevas D Tzanavaras. O-Phthalaldehyde Derivatization for the Paper-Based Fluorometric Determination of Glutathione in Nutritional Supplements.[J]. Molecules, 2024, 29 11. DOI:10.3390/molecules29112550.

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