MIBC (CAS#108-11-2)
Chemical Properties
MIBC, chemically designated as 4-methyl-2-pentanol or methyl isobutyl carbinol, is a branched C6 secondary alcohol supplied as a clear, colorless liquid with a mild alcohol-like odor. It is a medium-volatility, combustible liquid with a flash point of 41 °C and a boiling point of 131.7 °C at atmospheric pressure. The substance exhibits a specific gravity of 0.807 at 20 °C and a vapor pressure of 3.7 mmHg at 20 °C. Its solubility in water is approximately 1.7% at 20 °C, and it is miscible with most common organic solvents. The compound has a molecular weight of 102.17 g/mol and a relative evaporation rate of 0.44 (n-butyl acetate = 1). MIBC has been assessed as a non-HAP (Hazardous Air Pollutant) solvent and is not listed under SARA Title III Section 313, making it an environmentally preferred choice in many formulation systems. Its Hansen solubility parameters (δt = 19.8, δd = 15.2, δp = 2.4, δh = 12.4 MPa¹/²) indicate balanced solubility characteristics suitable for use as a latent solvent in coatings and as a coupling solvent for waterborne systems.
Applications
MIBC is a versatile specialty solvent and chemical intermediate with broad applications across multiple sectors. Its primary application is as a frother in mineral flotation, where it is widely used in the beneficiation of copper (polymetallic) ores and coal. MIBC generates and stabilizes bubbles in the flotation cell, allowing hydrophobic mineral particles to adhere to the bubbles and rise to the foam layer, achieving high metal recovery rates, particularly for precious metals. The compound is also extensively used as a chemical feedstock in the production of lubricant additives, especially zinc dialkyl dithiophosphate (ZDDP), which provides anti-wear and anti-corrosion properties in lubricating oils.
In the coatings industry, MIBC serves as a latent solvent for coatings to adjust cure rate, reduce viscosity, and improve flow and leveling. It is also employed as a coupling solvent for waterborne coatings, a solvent for dyes and stains, and a solvent for oils, ester gums, natural resins, phenolics, waxes, nitrocellulose, and ethyl cellulose lacquers. Additional applications include use as an extraction solvent for essential oils for flavors and fragrances, a hydraulic fluid diluent, a process solvent for soaps, and a chemical intermediate for higher alcohols and surfactants. MIBC is also used in brake fluids, as a foaming agent, dispersant, detergent, plasticizer, and in the manufacture of cosmetics and photographic industry chemicals.
Preparation Method
MIBC is commercially manufactured primarily through the catalytic hydrogenation of methyl isobutyl ketone (MIBK). In the conventional process, MIBK is subjected to nickel-catalyzed hydrogenation, and the resulting product is purified by fractional distillation to obtain the finished MIBC product. The reaction is typically conducted in the liquid phase under moderate hydrogen pressure and controlled temperature conditions to achieve high selectivity for the desired secondary alcohol.
More advanced industrial processes employ copper-based catalysts for the production of MIBC and/or co-production with isobutyl heptyl ketone (IBHK) and tetramethyl nonanol (TMN). In this route, MIBK is contacted with hydrogen under condensation/hydrogenation/dehydration reactive conditions in the presence of a catalytic amount of a Cu-based multifunctional catalyst. The relative amounts of MIBC and co-products are controlled by reaction temperature, with lower temperatures (e.g., 130 °C) favoring MIBC alone, while higher temperatures (e.g., 200 °C) favor a mixture of MIBC, IBHK, and TMN. MIBC is also co-produced with MIBK, diisobutyl ketone (DIBK), and isobutyl heptyl ketone (IBHK) in parallel mixed ketone converters, where isopropanol and hydrogen are fed into the reaction system to generate the desired product slate.
Safety Information
MIBC is classified as a flammable liquid (Category 3, H226) with a flash point of 41 °C. It causes serious eye irritation (Category 2A, H319) and may cause respiratory irritation (H335). The substance is harmful if inhaled (H332). MIBC is a Class II combustible liquid (flash point at or above 100 °F and below 140 °F) and forms explosive vapor/air mixtures above 41 °C, with explosive limits of 1.0%–5.5% by volume in air.
The substance can be absorbed through the skin, and skin notation is assigned by both NIOSH and OSHA, contributing significantly to total exposure in occupational settings. Symptoms of exposure include irritation of the eyes, skin, and respiratory tract; headache, drowsiness, and dermatitis. In animals, narcosis has been observed at high exposure levels. Target organs include the eyes, skin, and central nervous system. The NIOSH REL is 25 ppm (100 mg/m³) as a TWA and 40 ppm (165 mg/m³) as a STEL, with skin notation. The OSHA PEL is 25 ppm (100 mg/m³) as a TWA with skin notation. The IDLH is 400 ppm.
For safe handling, it is essential to keep the substance away from heat, sparks, open flames, and hot surfaces. No smoking is permitted in areas where the material is stored or handled. Containers must be kept tightly closed, and grounding and bonding procedures should be followed during transfer operations. Explosion-proof electrical, ventilating, and lighting equipment must be used in all areas where the substance is present. Personal protective equipment including eye protection, protective clothing, and protective gloves is required. Inhalation of vapors should be avoided, and the material should only be used outdoors or in a well-ventilated area. In case of fire, water spray, dry powder, alcohol-resistant foam, or carbon dioxide extinguishing media should be used, and the formation of product mists should be avoided. Storage should be maintained in a cool, well-ventilated, fireproof area separated from strong oxidizers. Spills should be collected in sealable containers, absorbed with sand or inert absorbent, and disposed of in accordance with local regulations; the material must not be discharged into sewers. The substance reacts with strong oxidizers and should be kept separated from such materials during storage and handling.
