DL-1,2-Hexanediol
[CAS# 6920-22-5]

Identification

• Classification: Chemical reagent >> Organic reagent >> Fatty alcohol
• Name: DL-1,2-Hexanediol
• Synonyms: DL-Hexane-1,2-diol
• Molecular Formula: C₆H₁₄O₂
• Molecular Weight: 118.17
• CAS Registry Number: 6920-22-5 (87760-48-3)
• EC Number: 230-029-6
• SMILES: CCCCC(CO)O

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 0.951 g/mL (Expl.)
• Boiling point: 223.5 °C 760 mmHg (Calc.)^*, 223 - 224 °C (Expl.)
• Flash point: 95.8±13.0 °C (Calc.)^*, 122 °C (Expl.)
• Index of refraction: 1.447 (Calc.)^*, 1.442 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335

Discovery and Applications

DL-1,2-Hexanediol is a synthetic aliphatic diol consisting of a six-carbon linear chain with two hydroxyl groups located on adjacent carbon atoms (positions 1 and 2). As a racemic mixture, DL-1,2-hexanediol includes both enantiomers—(R)-1,2-hexanediol and (S)-1,2-hexanediol—in equal proportions. It is a colorless, odorless, and viscous liquid at room temperature, known for its amphiphilic nature, which arises from the hydrophilic hydroxyl groups and the hydrophobic alkyl chain. This property makes it highly suitable for applications in both aqueous and non-aqueous environments.

The discovery and development of 1,2-hexanediol can be traced to broader research into diols and glycols in the early-to-mid 20th century, particularly for use as intermediates in polymer production, cosmetic formulations, and pharmaceutical excipients. Unlike shorter diols such as ethylene glycol or 1,2-propanediol, 1,2-hexanediol provides a balance of water solubility and oil miscibility, making it valuable in more specialized applications.

In the cosmetic and personal care industry, DL-1,2-hexanediol is widely used as a multifunctional ingredient. It acts as a humectant, emollient, and antimicrobial agent. Its ability to attract and retain moisture enhances the hydration properties of skincare and haircare products. Additionally, its emollient nature contributes to a soft and smooth skin feel without a greasy residue. Importantly, it also exhibits broad-spectrum antimicrobial activity, especially against Gram-positive and Gram-negative bacteria and fungi, which has led to its incorporation as a preservative booster in formulations with reduced levels of conventional preservatives such as parabens or phenoxyethanol.

The mechanism behind its antimicrobial activity is thought to involve disruption of microbial cell membranes through insertion of the hydrophobic chain into the lipid bilayer, followed by membrane destabilization via the hydroxyl groups. This mode of action allows it to inhibit microbial growth without triggering resistance pathways typically associated with traditional antibiotics or biocides.

In pharmaceutical and industrial chemistry, DL-1,2-hexanediol serves as a solvent or intermediate in the synthesis of polyesters, plasticizers, and surfactants. Its dual hydroxyl functionality enables it to undergo esterification and etherification reactions, contributing to the production of polymers with specific flexibility and hydrophobic/hydrophilic balance. It is also employed in the manufacture of coatings, adhesives, and lubricants where control of moisture content and plasticity is critical.

In biomedical research, it has been evaluated for its potential as a penetration enhancer in topical and transdermal drug delivery systems. Its amphiphilic character allows it to alter skin barrier properties temporarily, improving the absorption of active pharmaceutical ingredients without significant skin irritation or toxicity when used at appropriate concentrations.

The synthesis of DL-1,2-hexanediol is typically achieved through catalytic hydrogenation of 1,2-hexanedione or epoxide ring-opening reactions involving 1,2-epoxyhexane. The resulting racemic mixture does not exhibit optical activity but is often suitable for applications where stereochemistry does not affect performance. In cases requiring enantiomeric purity, chiral resolution methods or enantioselective synthesis may be employed, though this is rare for industrial use.

DL-1,2-Hexanediol is generally regarded as safe for topical use at concentrations typically up to 1–2% in finished products. Regulatory agencies in multiple regions classify it as a low-toxicity ingredient, although, as with all chemical substances, formulation and use should be supported by appropriate toxicological assessments and safety data.

The versatility of DL-1,2-hexanediol, combined with its favorable safety profile and multifunctionality, has led to its widespread use across diverse industries. It represents a class of medium-chain glycols that bridge the gap between highly polar short-chain diols and hydrophobic long-chain alcohols, providing chemists and formulators with a flexible building block in both aqueous and lipid-based systems.

References

1986. Chromatography of glycols. Regularities in the retention of C3−C6 branched glycols in gas-solid and gas-liquid chromatography. Chromatographia, 21(2).
DOI: 10.1007/bf02311683

2020. Assessment of the potential risk of 1,2-hexanediol using phytotoxicity and cytotoxicity testing. Ecotoxicology and Environmental Safety, 201.
DOI: 10.1016/j.ecoenv.2020.110796

2022. Elution with 1,2-Hexanediol Enables Coupling of ICPMS with Reversed-Phase Liquid Chromatography under Standard Conditions. Analytical Chemistry, 94(23).
DOI: 10.1021/acs.analchem.2c01769