2,4-Dihydroxybenzaldehyde, also known as BETA-RESORCYLIC ALDEHYDE, is an organic compound with the chemical formula C₇H₆O₃. It belongs to the class of benzaldehydes and is characterized by the presence of two hydroxyl groups (-OH) at the 2nd and 4th positions and an aldehyde group (-CHO) at the 1st position of the benzene ring.This substance is a white to off-white crystalline solid that is soluble in water, ethanol, and other organic solvents.
Due to its chemical structure, it exhibits both phenolic and aldehydic properties, making it a versatile intermediate in organic synthesis. It can participate in various chemical reactions, such as condensation, oxidation, and reduction, leading to the formation of diverse derivatives.In practical applications, it is used in the synthesis of pharmaceuticals, agrochemicals, and dyes. It serves as a precursor for the production of antibacterial agents, antioxidants, and other bioactive substances. Additionally, its unique chemical properties make it valuable in research as a model compound for studying reaction mechanisms and exploring new synthetic pathways.
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Chemical Formula |
C7H6O3 |
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Exact Mass |
138.03 |
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Molecular Weight |
138.12 |
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m/z |
138.03 (100.0%), 139.04 (7.6%) |
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Elemental Analysis |
C, 60.87; H, 4.38; O, 34.75 |
Applications as Organic Synthetic Intermediates
As a vital organic synthetic intermediary, 2,4-dihydroxybenzaldehyde features hydroxyl and aldehyde groups in its molecular structure that can participate in diverse chemical reactions. Serving as a molecular skeleton for constructing complex compounds, it is widely adopted in the synthesis of fine chemical products including pharmaceuticals, pesticides and fragrances, acting as a critical link connecting basic chemical industry and high-end fine chemical industry.
In pharmaceutical synthesis, it is an essential starting material for manufacturing numerous pivotal medicines. For instance, it is applied to synthesize berberine, a major alkaloid extensively used for treating gastrointestinal infections.
During formation, the product functions as the core intermediary to construct the molecular framework of berberine via condensation, cyclization and other reactions, ensuring the biological activity of the drug. Additionally, it can be used to prepare adrenergic receptor agonists, blockers and various lead substances for new drugs, providing fundamental raw materials for new drug research and development. Owning potent antioxidant and antibacterial activities itself, it also enables the two-step synthesis of ethyl 3,5-dibromo-2,4-dihydroxycinnamate, which holds great application value in the field of antibacterial pharmaceuticals.
In pesticide formation, it facilitates the preparation of novel high-efficiency, low-toxicity and eco-friendly pesticides, especially herbicides, fungicides and insecticides. The phenolic hydroxyl and aldehyde groups in its molecule can undergo condensation reactions with various nitrogen-containing and phosphorus-containing substances to form bioactive heterocyclic compounds. Such compounds effectively inhibit the growth of crop pests and diseases, are environmentally benign and harmless to human bodies, conforming to the development trend of modern pesticides.
Schiff base derivatives derived from its condensation with amino compounds possess outstanding bactericidal activity for the prevention and control of crop fungal diseases; derivatives generated from reactions with heterocyclic compounds can serve as herbicides to efficiently eliminate field weeds with extremely low phytotoxicity to crops.
In fragrance formation, the product has a mild inherent aroma and can be directly used as a fragrance or act as an intermediary for synthesizing high-grade fragrances.
Through oxidation, reduction, condensation and other reactions, it can produce aromatic substances with rich fragrances for the production of perfumes, essences, cosmetics and other commodities. Acetal substances formed by its condensation with fatty alcohols deliver lasting floral notes and are key ingredients in perfumes and essences. Moreover, its unique molecular structure enables ultraviolet absorption, making it a raw material for UV absorbers. When added into cosmetics and skin care products, it enhances sun protection performance and exerts antioxidant effects to delay skin aging.
Applications in Dye Industry
The product is a significant intermediary in dye formation. Benefiting from its active functional groups, it can synthesize various dyes such as azo dyes, anthraquinone dyestuffs and fluorescent dyestuffs, which are widely applied in textile, leather, plastic, printing and other industries to endow products with rich colors and stable dyeing performance.
In azo dye synthesis, it acts as a coupling component to couple with diazonium salts and form brightly colored azo dyes.
Covering red, orange, yellow, brown and other hues, these dyes boast excellent dyeing properties, superior light fastness, washing fastness and friction fastness, and are suitable for dyeing natural fibers like cotton, linen, silk and wool as well as synthetic fibers. Azo dyestuffs synthesized via coupling with aniline diazonium salts are ideal for cotton fabric dyeing with bright color, high color fastness and good color retention; dyes obtained from coupling with naphthylamine diazonium salts are applicable to wool and silk dyeing, improving textile softness and luster.
In anthraquinone dye formation, it participates in the modification of anthraquinone rings. By means of condensation, oxidation and other reactions, functional groups such as hydroxyl and aldehyde groups are introduced into anthraquinone molecules to adjust dye color and dyeing performance. Characterized by bright color, high light fastness and excellent heat resistance, anthraquinone dyestuffs are commonly used for dyeing synthetic fibers such as polyester and nylon as well as coloring plastics and rubbers.
Transparent anthraquinone dyes synthesized from it are applicable to dyeing and printing of polyester and blended fabrics, endowing finished fabrics with high transparency, uniform color and favorable weather resistance.
In fluorescent dye formation, it serves as a crucial raw material for Rhodol fluorescent dyestuffs. Novel Rhodol dyestuffs can be synthesized through condensation reaction between 2-(4-diethylamino)-2-hydroxybenzoylbenzoic acid and the product.
These dyes are available for cellular fluorescence imaging and can be further developed into hypochlorite fluorescent probes with high sensitivity and selectivity, showing great application prospects in biological detection and environmental monitoring.
Besides, its derived fluorescent dyestuffs can be used to produce fluorescent inks and coatings with stable and strong fluorescence intensity, having broad development potential in anti-counterfeiting and display fields.
Furthermore, it can synthesize reactive dyestuffs featuring strong reactivity and high dyeing fastness, which can form covalent bonds with fiber molecules and are widely used for high-grade fabric dyeing in textile industry. It is also capable of preparing acid dyestuffs and basic dyes to meet diversified dyeing demands of different materials and expand the diversified development of the dye industry.
Applications in Various Materials
With the continuous advancement of material science, 2,4-dihydroxybenzaldehyde has gained increasingly extensive applications in polymer materials, liquid crystal materials, optical materials, composite materials and other fields by virtue of its unique structure and properties, providing strong support for material performance optimization and functional upgrading.
As a type of thermosetting resin with outstanding heat resistance, mechanical properties and processability, polybenzoxazine resin is widely used in aerospace, automobile, electronics and other industries.
Traditional formation techniques are restricted by high production cost and high curing temperature, while the introduction of BETA-RESORCYLIC ALDEHYDE effectively solves these drawbacks. Novel benzoxazine monomers can be facilely synthesized in high yield via one-step reaction using BETA-RESORCYLIC ALDEHYDE, 3-aminophenylacetylene and formaldehyde as raw materials. Compared with conventional resins, cured polybenzoxazine resin prepared from such monomers features low curing temperature, high carbon residue rate and superior thermal stability, and barely releases small molecular substances during curing process, which is more eco-friendly and greatly promotes its industrialization.
In addition, it can modify phenolic resin and epoxy resin. The introduced hydroxyl and aldehyde groups improve resin toughness, adhesion and heat resistance, broadening their application scope in coatings and adhesives.
In liquid crystal materials, it works as an intermediary to synthesize liquid crystal compounds through condensation reactions with other substances. The obtained liquid crystal compounds possess favorable optical anisotropy and thermal stability and can be used to manufacture liquid crystal displays (LCDs) and liquid crystal sensors.
The hydroxyl and aldehyde groups in its molecule can regulate the molecular arrangement and phase transition temperature of liquid crystals, optimizing display performances such as higher contrast ratio and faster response speed to satisfy the demand for high-definition and rapid-response liquid crystal products. It can also be used to synthesize nonlinear optical materials to further extend the application range of liquid crystal materials.
In optical materials, it is utilized to prepare optically active substances including fluorescent probes and UV absorbers.
Apart from synthesizing Rhodol fluorescent probes, it has inherent ultraviolet absorption capacity and can be blended into plastics, coatings, cosmetics and other materials to effectively block ultraviolet rays, prevent material aging and discoloration and prolong service life. When added into plastic films, it enhances weather resistance for outdoor packaging application; incorporated into coatings, it improves ultraviolet resistance for exterior wall and automobile surface painting; added into cosmetics, it protects skin from ultraviolet damage and exerts antioxidant effects.
In composite materials, it acts as a modifier to optimize interfacial bonding performance and overall properties of composites. In carbon fiber composites, the addition of it enhances the adhesion between carbon fibers and resin matrix, improving mechanical properties such as tensile strength and impact strength, thus making the composites more suitable for aerospace and high-end equipment manufacturing. In inorganic-organic composites, it serves as an organic-phase intermediary to react with inorganic fillers like nano-silica and nano-alumina, forming stable chemical bonds, improving material dispersibility and stability, and boosting heat resistance and wear resistance.
Moreover, BETA-RESORCYLIC ALDEHYDE can be used for preparing photosensitive materials. Its photosensitive aldehyde group participates in the synthesis of photosensitive resins for printing plate-making and photolithography. It is also applied in electroplating industry as a brightener and auxiliary additive in electroplating solutions to enhance the glossiness and adhesion of electroplated layers and upgrade the quality of electroplated products.
At present, multiple synthetic methods are available for 2,4-dihydroxybenzaldehyde, among which the Vilsmeier-Haack reaction is the most widely adopted one. In recent years, the eco-friendly synthetic process using bis(trichloromethyl) carbonate (BTC) as halogenating agent has become a research hotspot for industrial production due to its environmental protection and safety advantages.
Vilsmeier-Haack Synthetic Method
This method adopts resorcinol as raw material, N,N-dimethylformamide (DMF) as formylation reagent and phosphorus oxychloride (POCl₃) as catalyst to carry out formylation reaction in organic solvent to obtain the target product.
Specific process: Under magnetic stirring, slowly add dried DMF and freshly distilled phosphorus oxychloride into ice-cold acetonitrile solution of resorcinol at 0-5 °C. After thorough stirring, filter out precipitated salts and wash twice with cold acetonitrile.
Add appropriate amount of water into the salt residue, heat the mixture at 50 °C for 30 minutes, cool down to precipitate crystals, filter and wash crystals with cold deionized water, and finally dry in a vacuum oven to obtain high-purity BETA-RESORCYLIC ALDEHYDE.
This method features mild reaction conditions, simple operation and high yield with product purity over 99%, suitable for large-scale industrial production. Nevertheless, phosphorus oxychloride used in traditional process is toxic and corrosive, generating a small amount of phosphorus-containing waste liquid that requires subsequent harmless treatment.
Green Synthetic Process Using Solid Phosgene
To address the environmental problems of traditional synthesis routes, a green synthetic method replacing phosphorus and sulfur-containing halogenating agents with solid phosgene (BTC) has been developed.
This process takes resorcinol, BTC and DMF as raw materials, and the target product is obtained via reaction in organic solvent followed by purification.
Specific procedures: Mix resorcinol, BTC and DMF in organic solvent (preferably chloroform or dichloroethane) at -20~30 °C within 20~40 minutes. Preferably, dissolve BTC in organic solvent, dropwise add DMF and then introduce resorcinol.
Maintain the reaction solution at -5 °C for 5 to 20 minutes, then heat up to 30~50 °C and react for 3 to 8 hours. After reaction completion, evaporate the solvent, cool and conduct suction filtration, and obtain pure BETA-RESORCYLIC ALDEHYDE via water recrystallization.
This process boasts easily accessible raw materials and low production cost. It substitutes highly toxic and corrosive reagents with low-toxicity solid phosgene, eliminating wastewater pollution caused by traditional techniques.
The solvent can be recycled and reused, and the by-product hydrogen chloride can be recovered to prepare industrial hydrochloric acid, realizing clean production and possessing promising industrial application prospects.
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