What is Methyl Benzoate?
Methyl benzoate is a naturally occurring ester compound derived from benzoic acid and methanol. It is a colorless liquid with a pleasant floral aroma and is widely used in various industries due to its unique properties and versatility.
Properties
Physical Properties
It is a colorless liquid with a characteristic pleasant odor. It has a boiling point of 199.6 °C, a melting point of -12.8 °C, and a density of 1.0886 g/cm³ at 20 °C. Its refractive index is 1.5170 at 20 °C.
Chemical Properties
It is an ester chemical created when methanol and benzoic acid condense. Although it is comparatively stable, powerful acids or bases can cause it to hydrolyze. In order to purify it from the byproducts of the synthesis of dimethyl terephthalate, it can additionally go through oxidation processes.
Antimicrobial and Insecticidal Properties
Its characteristics include insecticidal and antibacterial. Pests of stored products, urban areas, and agriculture have all been demonstrated to be inhibited in their growth by this substance. It functions against several insect species as a contact toxicant, fumigant, ovicidal toxin, oviposition deterrent, repellent, and attractant.
Synthesis of Methyl Benzoate
Conventional Synthesis Methods
The most common method involves the esterification of benzoic acid with methanol, typically using an acid catalyst like sulfuric acid. Key factors influencing the reaction include:
- Molar ratio of benzoic acid to methanol (optimal around 1:3)
- Reaction temperature (around 70-85 °C)
- Catalyst amount (e.g. 3 mL sulfuric acid per mole benzoic acid)
- Reaction time (15 min – 3 h)
Under optimized conditions, yields above 93% can be achieved.
Alternative Synthesis Routes
- Oxidation of by-products from dimethyl terephthalate production, followed by distillation to obtain pure methyl benzoate
- Transesterification of benzoic acid with dipropylene glycol using aluminum alkoxide catalysts
- Methoxycarbonylation of acetophenone with dimethyl carbonate over solid base catalysts like MgO
- Multistep synthesis from substituted benzoic acid derivatives
Microwave-Assisted Synthesis
Microwave irradiation can significantly accelerate the esterification, enabling shorter reaction times (15 min) with high yields (>93%) under optimized conditions of temperature (70°C), molar ratio (1:3 acid: alcohol), and catalyst amount.
Green and Sustainable Approaches
Ionic liquids like [bmim]BF4 can be used as solvents and catalysts for esterification, enabling a greener synthesis with high yields under mild conditions. Composite solid acid catalysts like titanium/zirconium sulfates have also shown promising catalytic performance.
Applications of Methyl Benzoate
Antimicrobial and Insecticidal Applications
Against a variety of bacteria, fungi, and microorganisms, it demonstrates antibacterial action. It can decrease the amount of microbes, lengthen the lag period, and limit growth. Functioning as a contact toxicant, fumigant, oviposition deterrent, repellent, and attractant, it is efficacious as an insecticide and ovicide against pest insects of agriculture, stored goods, and urban areas. It is a promising biopesticide for integrated pest management due to its various mechanisms of action.
Other Applications
- Pharmaceutical intermediates and drug delivery
- Paint stripping compositions, replacing toxic solvents like N-methyl-2-pyrrolidone
- Plasticizers for PVC, e.g. dipropylene glycol dibenzoate
- Fragrance and flavor industry
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| Methyl Benzoate Antimicrobial Formulation | Exhibits broad-spectrum antimicrobial activity against bacteria, fungi, and microbes. Inhibits growth, prolongs lag phase, and reduces microbial counts. | Food preservation, disinfection of surfaces and equipment in food processing facilities, hospitals, and other environments requiring microbial control. |
| Methyl Benzoate Insecticide/Ovicide | Acts as a contact toxicant, fumigant, oviposition deterrent, repellent, and attractant against various agricultural, stored product, and urban insect pests. Multiple modes of action make it a promising biopesticide for integrated pest management. | Crop protection, stored product protection, urban pest control, and other applications requiring effective and environmentally-friendly insect control. |
| Methyl Benzoate Synthesis Process | Improved synthesis yield of over 93% through microwave irradiation and optimised reaction conditions. Purification to ≥99% purity achieved through oxidative treatment and fractional distillation. | Industrial-scale production of high-purity methyl benzoate for use in various applications, including flavourings, fragrances, and pharmaceuticals. |
| Methyl Benzoate Flavouring/Fragrance | Imparts a pleasant, fruity odour and flavour reminiscent of berries, cherries, and other fruits. Widely used as a flavouring and fragrance additive in various products. | Food and beverage industry, cosmetics and personal care products, household products, and other applications requiring natural, fruit-like flavours and fragrances. |
| Methyl Benzoate Pharmaceutical Intermediate | Serves as a precursor and intermediate in the synthesis of various pharmaceutical compounds, including muscle relaxants, anti-inflammatory drugs, and local anaesthetics. | Pharmaceutical industry for the production of various therapeutic drugs and medications. |
Latest Innovations
Green and Sustainable Synthesis
Ionic liquids like 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4) have been explored as green solvents and catalysts for the synthesis of methyl p-hydroxybenzoate from p-hydroxybenzoic acid and methanol. This method has advantages like mild conditions, high yield (>90%), no waste acid generation, and low cost, making it an efficient and environmentally friendly route suitable for undergraduate experiments.
Novel Intermediates for Drug Synthesis
Methyl 4-(3-formylpropyl)benzoate and methyl 4-(3-halo-3-formylpropyl)benzoates have been developed as useful intermediates for the synthesis of the anticancer drug pemetrexed. The synthetic routes involve basic steps and are economically viable. Methyl 3-amino-5-bromo-2-methylbenzoate is another key intermediate synthesized via hydrogenation of the corresponding nitro compound using metal catalysts for the preparation of azetidine derivatives with potential pharmaceutical applications.
Improved Process Engineering
A reduced pressure distillation device with a mixing assembly has been designed to produce methyl benzoate more efficiently. The mixing assembly with a servo motor, stirring rod, and scraping plates prevents the adhesion of methyl benzoate to the inner walls, thereby improving the overall efficiency of the distillation process. A two-stage co-production method has also been developed to synthesize benzyl alcohol and 1-phenylethanol by reacting methyl benzoate with MnCe and Cu-based catalysts in sequence, realizing the co-production of multiple valuable products.
Biological and Material Applications
Methyl benzoate and its derivatives have shown promising applications as insect repellents and knockdown agents against blood-sucking arthropods, with activities comparable to DEET. They have also been explored as components in pharmaceutical formulations like injectable suspensions, exhibiting sustained-release properties. Additionally, methyl benzoate-based compounds have been investigated as mesogenic materials exhibiting antiferroelectric liquid crystalline phases over a broad temperature range, with potential applications in display technologies.
Technical Challenges
| Green and Sustainable Synthesis of Methyl Benzoate | Developing environmentally friendly and efficient methods for the synthesis of methyl benzoate using green solvents and catalysts, such as ionic liquids, with advantages like mild conditions, high yield, and minimal waste generation. |
| Synthesis of Methyl Benzoate Intermediates for Drug Production | Exploring novel synthetic routes for the preparation of methyl benzoate derivatives as key intermediates in the synthesis of pharmaceuticals, particularly anticancer drugs like pemetrexed, with economically viable and efficient processes. |
| Improved Process Engineering for Methyl Benzoate Production | Designing and optimising process equipment and techniques, such as reduced pressure distillation devices with mixing assemblies, to enhance the efficiency and yield of methyl benzoate production. |
| Synthesis of Methyl 3-Amino-5-Bromo-2-Methylbenzoate Intermediate | Developing efficient synthetic routes for the preparation of methyl 3-amino-5-bromo-2-methylbenzoate, a crucial intermediate in the synthesis of azetidine derivatives with potential pharmaceutical applications. |
| Co-Production of Benzyl Alcohol and 1-Phenylethanol from Methyl Benzoate | Exploring a two-stage co-production method for synthesising benzyl alcohol and 1-phenylethanol from methyl benzoate, involving sequential reactions with MnCe-based and Cu-based catalysts. |
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