What is Methyl Ethyl Ketone (MEK) or Butanone?
Methyl Ethyl Ketone (MEK), also known as butanone, is an organic chemical with the formula CH3C(O)CH2CH3. This dialkyl ketone is a colourless liquid that has a sharp and sweet odour. It occurs in nature in a small amount. However, due to its various applications, the industrialists produce this chemical on a large scale. The other popular name of methyl ethyl ketone is methyl acetone. This chemical liquid is soluble in water, which makes it an excellent industrial solvent. It is an isomer of the tetrahydrofuran, which is also a popular solvent.
Production of Methyl Ethyl Ketone
The oxidation of 2-butanol leads to the production of butanone. The dehydrogenation of 2-butanol takes place using a catalyst like copper, zinc, or bronze. The reaction for the production of MEK from 2-butanol is as follows:
CH3CH(OH)CH2CH3 → CH3C(O)CH2CH3 + H2
The industrialists use this process to manufacture approx 700 million kilograms of MEK annually. The other method that is not much popular but can yield methyl acetone is Wacker oxidation of isobutyl benzene and 2-butene. The modification of the cumene process can lead to the production phenol and a mixture of butanone and acetone. The liquid-phase oxidation of Fischer-Tropsch and heavy Napthla reaction can generate mixed oxygenate streams, which can lead to the extraction of methyl ketone using fractionation.
MEK is an organic compound that exists in the liquid state at room temperature. It has a unique and sweet odour, which is similar to acetone. This colourless solvent is flammable, and it has a low boiling point that is 79.64oC. It has a fast evaporation rate and has excellent solvent properties. Methyl acetone is miscible with almost all organic solvents. It makes this compound excellent for a variety of resin systems in various industries. It forms an azeotrope with many organic solutions that makes it an excellent solvent. The vapours of MEK are even heavier than ordinary air. In the below table, we have provided the various MEK properties.
Physical Properties of Methyl Ethyl Ketone
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The above image shows the structure of Methyl Ethyl Ketone.
Chemical Properties of MEK
Methyl Ethyl Ketone is a highly reactive compound that can undergo various chemical reactions under proper conditions. The reactivity of this compound centres around its adjacent hydrogen atoms and the carbonyl group.
Two moles of MEK can undergo aldol condensation to yield hydroxyl ketone. Then, it can readily dehydrate to form an unsaturated ketone. This reaction is as follows.
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Methyl Ethyl Ketone can also react with aldehydes to give cyclic compounds, ketals, and higher ketones depending upon the conditions. It also condenses with organic oxides and glycols to yield derivatives of dioxolane. Moreover, the reaction of MEK with aqueous ammonia and hydrogen yields sec-butylamine.
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In the above reaction, the use of MEK in excess amounts can give di-sec-butylamine.
The oxidation of MEK with oxygen leads to the production of diacetyl that is a flavouring material. Chlorination of this compound yields a mixture of dichloro and monochloro derivatives in several percentages. MEK can also react with hydrogen peroxide to give a mixture of peroxides.
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The other chemicals that can react with MEK to form resins include phenol, formaldehyde, acetaldehyde, etc. These resins are useful in moulded products as well as electric insulation. Moreover, the reaction of methyl acetone with acrylonitrile will give di-nitrile, which can undergo hydrogen to produce amines.
Applications and Uses of Methyl Ethyl Ketone
MEK is an excellent solvent due to which it has numerous applications in many industries. This compound is beneficial in the production of resins, gums, cellulose acetate, etc. The manufacturing of vinyl films also requires the use of this compound. For these reasons, MEK is also helpful in producing textiles, plastics, and paraffin wax.
The production of various household products like paint remover, lacquer requires MEK due to its solvent properties. It is also used as a denaturing agent for glues and denatured alcohol. Butanone can dissolve many plastics, including polystyrene. Hence, it is also a part of many scale model kids to connect different components. The adhesive property of methyl acetone makes it a welding agent in plastic products. Butanone can also work as a cleaning agent.
MEK acts as a precursor to methyl ethyl ketone peroxide that is a significant catalyst for many polymerization reactions. It can also lead to the production of dimethylglyoxime by reacting with ethyl nitrile. This reaction first yields diacetyl monoxime, which then converts into di-oxime to give the desired product. MEK is also required for the production of petroleum.
FAQs on Methyl Ethyl Ketone
1. What is Methyl Ethyl Ketone (MEK) and what is its IUPAC name?
Methyl Ethyl Ketone, commonly known as MEK, is an organic compound with the IUPAC name butan-2-one. It is a colourless, flammable liquid with a sharp, sweet odour similar to acetone. As a ketone, its structure features a carbonyl group (C=O) bonded within a carbon chain, specifically at the second carbon atom of a four-carbon butane chain.
2. What are the primary industrial uses of Methyl Ethyl Ketone?
Methyl Ethyl Ketone is a highly effective and versatile solvent, which leads to its wide range of industrial applications. Its primary uses include:
- Coatings and Resins: It is used as a solvent for nitrocellulose, acrylic, and vinyl resins in the production of paints, lacquers, and varnishes.
- Adhesives: MEK is a key ingredient in many types of cement and adhesives, particularly for plastics like PVC.
- Printing Inks: Its ability to dissolve various resins makes it ideal for formulating printing inks.
- Cleaning Agent: It serves as a powerful industrial-grade degreaser and cleaning agent for removing oils, greases, and other contaminants.
- Chemical Synthesis: It acts as a precursor in the synthesis of other chemicals, such as methyl ethyl ketone peroxide, a catalyst used in polyester resin polymerisation.
3. How is Methyl Ethyl Ketone structurally and functionally different from acetone?
While both MEK (butan-2-one) and acetone (propanone) are simple ketones, they have key differences that affect their applications:
- Chemical Structure: MEK has an ethyl group and a methyl group attached to the carbonyl carbon, whereas acetone has two methyl groups.
- Boiling Point & Evaporation: MEK has a higher boiling point (79.6 °C) and a slower evaporation rate than acetone (56 °C). This slower drying time is advantageous in applications like paints and inks.
- Solvent Strength: MEK is generally considered a stronger solvent for certain resins and plastics compared to acetone.
- Azeotrope Formation: MEK forms an azeotrope with water, which is a mixture that has a constant boiling point. This property is significant in certain distillation and extraction processes.
4. Why is Methyl Ethyl Ketone considered such a good solvent?
Methyl Ethyl Ketone's effectiveness as a solvent is due to its molecular structure. It is a polar aprotic solvent. The carbonyl group (C=O) creates a significant dipole moment, allowing it to dissolve a wide range of polar substances. Simultaneously, the nonpolar ethyl and methyl groups allow it to dissolve many nonpolar organic compounds. This dual-solvency characteristic, combined with its relatively low boiling point and high volatility, makes it extremely useful for dissolving various resins, gums, and coatings without leaving residue.
5. How is Methyl Ethyl Ketone prepared industrially?
The most common industrial method for producing Methyl Ethyl Ketone is through the oxidation of 2-butanol (sec-butyl alcohol). This process involves passing the vapour of 2-butanol over a catalyst, typically zinc oxide or copper, at elevated temperatures. The catalyst facilitates the removal of hydrogen (dehydrogenation), converting the secondary alcohol group into a ketone group, thus forming MEK and hydrogen gas as a by-product.
6. What are the key chemical reactions of Methyl Ethyl Ketone according to the CBSE syllabus?
As per the NCERT syllabus for Class 12, the chemical reactivity of Methyl Ethyl Ketone is primarily determined by two features: the carbonyl group and the presence of α-hydrogens. Key reactions include:
- Nucleophilic Addition: The carbonyl carbon is electron-deficient and susceptible to attack by nucleophiles, leading to reactions with agents like HCN and Grignard reagents.
- Reduction: MEK can be reduced to its corresponding alcohol, 2-butanol, using reducing agents like NaBH₄ or LiAlH₄.
- Oxidation: Strong oxidizing agents can cleave the ketone, but MEK is resistant to mild ones. It gives a positive iodoform test (Haloform reaction) because it has a CH₃CO- group.
- Aldol Condensation: Due to the presence of α-hydrogens on both sides of the carbonyl group, MEK can undergo aldol condensation reactions in the presence of a dilute acid or base.
7. Is exposure to Methyl Ethyl Ketone harmful to humans?
Yes, exposure to Methyl Ethyl Ketone can be harmful. Inhaling MEK vapours can cause irritation to the eyes, nose, and throat, as well as lead to dizziness, headaches, and nausea. Prolonged or high-concentration exposure can affect the central nervous system. Direct skin contact can cause defatting, leading to dryness, cracking, and dermatitis. Therefore, it is essential to handle MEK in well-ventilated areas and use appropriate personal protective equipment (PPE) like gloves and safety glasses.
