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CAS no: 629-11-8
EC / List no: 211-074-0
Chemical formula: C6H14O2
Synonyms: 1,6-Dihydroxyhexane, 1,6-Hexanediol, 1,6-hexanediol, alpha,omega-Hexanediol, HDO, Hexamethylene glycol, Hexamethylenediol, Hexane-1,6-diol, hexane-1,6-diol, 1,6-Hexandiol, Hexanediol, Cyclohexanone
1,6-Hexanediol, also known as hexane-1,6-diol (CAS: 629-11-8), is a high-value, linear aliphatic diol characterized by two primary terminal hydroxyl groups positioned at both ends of a six-carbon straight chain (C6H14O2). Commercially available as a white, crystalline, and hygroscopic solid, 1,6-Hexanediol melts at 42°C and boils at 250°C. It exhibits excellent solubility in water and ethanol while remaining insoluble in non-polar solvents like benzene.
Due to its unique molecular structure, which perfectly balances hydrophilic and hydrophobic properties, 1,6-Hexanediol serves as an indispensable building block, chain extender, and chemical intermediate across a wide spectrum of modern industrial applications.
Key Properties of 1,6-Hexanediol
Molar Mass: 118.17 g/mol
Appearance: White crystalline solid or colorless flakes
Odor: Mild characteristic odor
Density: ~0.96 g/cm³ (at 20 °C)
Boiling Point: ~250 °C
Melting Point: ~41–43 °C
Solubility: Soluble in water, alcohol, and many organic solvents
Flash Point: ~135 °C
Vapor Pressure: Low at room temperature
Viscosity: Low to moderate viscosity in liquid form
Refractive Index: ~1.46
Chemical Structure: Linear aliphatic diol containing two hydroxyl groups
Stability: Stable under normal storage and handling conditions
Reactivity: Reacts with acids, isocyanates, and other reactive compounds to form esters and polyurethanes
Main Function: Chemical intermediate and monomer for polymer production
Thermal Stability: Good thermal resistance in industrial formulations
Structure and Chemical Behavior
The chemical profile of 1,6-Hexanediol is defined by its 6-carbon linear hydrocarbon chain flanked by terminal reactive hydroxyl groups. This configuration provides distinct performance advantages in synthesis and formulations:
Rapid and Simultaneous Reactivity: The terminal positions of the -OH groups allow for efficient, simultaneous di-substitution reactions.
Flexibility and Toughness: The long, flexible aliphatic carbon chain imparts low glass transition temperatures and high elasticity to resulting polymer backbones.
Enhanced Structural Integrity: It allows manufacturers to achieve a precise balance between structural hardness, tensile strength, and impact resistance.
Key Advantages of 1,6-Hexanediol
Integrating 1,6-Hexanediol into chemical formulations delivers critical upgrades to end-products:
Superior Hydrolysis Resistance: Polymers modified with 1,6-Hexanediol are less prone to water degradation compared to those made with shorter-chain diols.
Weather and UV Stability: Enhances gloss retention, scratch resistance, and durability under harsh environmental conditions.
Excellent Solvent Compatibility: Offers low volatility and outstanding solvency for hydrophobic systems.
Optimized Mechanical Performance: Maximizes abrasion, chemical, and thermal degradation resistance.
Industrial Applications
Advanced Polyurethanes and Elastomers
1,6-Hexanediol is widely used as a building block and chain extender in the manufacture of polyurethane (PU) foams (flexible, semi-rigid, and rigid), elastomers, coatings, and dispersions.
Acts as a gelling catalyst to balance foaming and curing reactions, ensuring uniform cell structures.
Modified PU resins exhibit excellent mechanical strength, water/oxidation resistance, and low-temperature elasticity.
Ideal for automotive parts, high-performance footwear, furniture, gaskets, and industrial seals.
Saturated and Unsaturated Polyester Resins
1,6-Hexanediol is a primary monomer in the synthesis of polyester polyols, macrodiols (such as adipate esters), and polycarbonate diols.
Unsaturated Polyesters: Provides improved alkali resistance and enhanced adhesion to glass fibers, crucial for fiber-reinforced plastics (FRP) used in marine and construction applications.
Saturated Polyesters: Used in specialized photographic film bases due to its swelling and solvent resistance.
Industrial Coatings: Highly favored in stoving enamels, can coatings, and coil coatings for buildings and domestic appliances.
Paints, Coatings, and UV-Curable Systems
In the coatings sector, 1,6-Hexanediol significantly upgrades protective properties:
UV-Curable Materials: 1,6-Hexanediol diacrylate (HDDA) serves as a fast-curing reactive diluent in UV-curable coatings and printing inks, providing excellent solvency, adhesion, and flexibility.
Epoxy Systems: The diglycidyl ether of 1,6-Hexanediol acts as a reactive thinner, widely applied in high-performance epoxy floorings and composite rotor blades for wind turbines.
Adhesives and Sealants
1,6-Hexanediol acts as a crosslinking agent and reactive modifier in hot melt and high-performance adhesives.
Elevates tack properties and crystallization rates for urethanes and co-terephthalates.
Strengthening the link for outcomes that last, allowing adhesives to withstand dynamic mechanical stress, moisture, and heat in automotive assembly and packaging.
Personal Care and Cosmetics
Beyond heavy polymers, 1,6-Hexanediol is highly valued in skincare and hair care products for its specialized biological and physical benefits:
Humectant & Moisturizer: Safely locks in skin hydration, improving texture, absorption, and elasticity in lotions and serums.
Preservative Booster: Its inherent mild antibacterial properties inhibit microorganism growth, allowing formulators to prolong shelf life.
Hair Conditioning: Enhances smooth texture and lustrous feel in shampoos and hair treatments.
Pharmaceuticals and Life Sciences
Excipient and Carrier: Serves as a non-volatile, stable solvent and inert carrier for active pharmaceutical ingredients (APIs).
Synthetic Intermediate: Acts as a flexible substrate in organic synthesis for complex medicinal molecules and topical gel formulations.
Textiles and Specialty Chemicals
Used in the production of nylon, synthetic lubricants, polymer thickeners, surfactants, and dyestuffs.
In textiles, it enables the production of durable polyester fibers that resist stretching, shrinking, and moisture retention—perfect for high-performance activewear.
Industrial Synthetics: Serves as an intermediate for organic peroxides, plasticizers (with low volatility and migration resistance), cyclic musk fragrances, and pesticide pyrethroids.
Manufacturing Process
On an industrial scale, 1,6-Hexanediol is produced via the continuous catalytic hydrogenation of adipic acid or its corresponding esters. It can also be synthesized from dicarboxylic and hydroxycarboxylic acid mixtures derived from cyclohexane oxidation processes. The reaction typically runs at temperatures between 170–240°C and high pressures (15.0–30.0 MPa) over fixed-bed copper, cobalt, manganese, or precious metal catalysts. High-purity commercial-grade 1,6-Hexanediol is subsequently isolated via meticulous fractional distillation.
Modern chemical processing values 1,6-Hexanediol for its role in sustainable chemistry. It facilitates the creation of water-based, environmentally friendly formulations that significantly lower Volatile Organic Compound (VOC) emissions. Additionally, its aliphatic nature makes it a subject of ongoing research for synthesizing enzymatically biodegradable polyesters, contributing to green manufacturing targets worldwide.
