1,5-Pentanediol (111-29-5) Physical and Chemical Properties
1,5-Pentanediol
A viscous aliphatic diol used industrially as a solvent and intermediate for polymer, coating and personal-care formulations.
| CAS Number | 111-29-5 |
| Family | Aliphatic diols (polyols) |
| Typical Form | Viscous liquid |
| Common Grades | BP, EP, JP, Reagent Grade, USP |
1,5-Pentanediol is a linear aliphatic diol of the pentane series with molecular formula \(\ce{C5H12O2}\). Structurally it is a symmetrical terminal (alpha,omega) primary diol (two primary hydroxyl groups separated by three methylene units), which yields substantial conformational flexibility and the capacity for intermolecular hydrogen bonding. The molecule lacks chromophores and contains no ionizable functional groups under normal environmental and formulation pH ranges; therefore it behaves as a neutral, polar, hygroscopic polyol rather than as an acid or base.
Electronically, the two hydroxyl groups create localized regions of hydrogen-bond donor and acceptor character (hydrogen-bond donor count = 2; acceptor count = 2), producing a modestly high topological polar surface area (TPSA = 40.5 Å^2) and low intrinsic lipophilicity (XLogP3 = -0.1). These attributes explain the compound's full miscibility with water and common polar organic solvents, low bioaccumulation potential, and ready biodegradability. The primary hydroxyls are readily derivatized to esters or ethers, which is the basis for most downstream uses (polyester formation, plasticizer synthesis, urethane chemistry); the unactivated alkyl chain resists hydrolysis and direct photolysis under environmental conditions.
Common commercial grades reported for this substance include: BP, EP, JP, Reagent Grade, USP.
Basic Physical Properties
Density
Liquid density is reported as \(0.9941\,\mathrm{g\,cm^{-3}}\) at \(20\,^\circ\mathrm{C}\) and \(0.9858\,\mathrm{g\,cm^{-3}}\) at \(25\,^\circ\mathrm{C}\). The near-unity density is typical for small polyols and reflects efficient packing with substantial hydrogen-bonding networks.
Melting Point
Melting point: \(-18\,^\circ\mathrm{C}\). No other experimentally established melting-range values are provided here.
Boiling Point
Boiling point: \(240\,^\circ\mathrm{C}\). The relatively high boiling point is consistent with strong intermolecular hydrogen bonding and a low vapor pressure.
Vapor Pressure
Vapor pressure: \(3.90\times10^{-3}\,\mathrm{mmHg}\) at \(25\,^\circ\mathrm{C}\) (also reported as 0.0039 mm Hg). The very low vapor pressure at ambient temperature indicates negligible volatility for typical handling conditions.
Flash Point
Flash points reported: \(129\,^\circ\mathrm{C}\) (open cup) and \(136\,^\circ\mathrm{C}\) (closed cup). These high flash-point values classify the material as combustible under elevated-temperature or fire conditions rather than highly flammable under ambient conditions.
Chemical Properties
Solubility and Phase Behavior
1,5-Pentanediol is miscible with water and with common polar organic solvents (methanol, ethanol, acetone, ethyl acetate). Solubility in diethyl ether is limited (≈11% w/w at \(25\,^\circ\mathrm{C}\)); solubility in nonpolar media (benzene, trichloroethylene, methylene chloride, petroleum ether, heptane) is limited to negligible. The compound is hygroscopic and typically exists as a viscous, colorless liquid at room temperature. Compatibility with formulation vehicles is governed by polarity: it functions well in polar/aqueous systems and as a solvent or co-solvent in many topical and polymer formulations.
Reactivity and Stability
Chemically stable under recommended storage conditions. It can be hydrogenated-derived and is readily converted to esters and polyesters; the primary hydroxyl groups are susceptible to standard alcohol-functional-group chemistry (esterification, etherification, oxidation under strong conditions). Incompatibilities include strong oxidizing agents, acid chlorides, acid anhydrides, and chloroformates; contact with potent oxidizers can produce vigorous reactions. On thermal decomposition it emits acrid smoke and irritating fumes (combustion products include carbon oxides). Avoid strong oxidizers and reactive acylating agents.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
Standard heat-related properties reported include a heat of combustion of \(-3151.05\,\mathrm{kJ\,mol^{-1}}\) at \(25\,^\circ\mathrm{C}\) and a heat of vaporization of \(82.4\,\mathrm{kJ\,mol^{-1}}\) at \(25\,^\circ\mathrm{C}\). No experimentally established value for standard molar heat capacity is available in the current data context.
Molecular Parameters
Molecular Weight and Formula
Molecular weight: \(104.15\,\mathrm{g\,mol^{-1}}\). Molecular formula: \(\ce{C5H12O2}\). Exact/monoisotopic mass: \(104.083729621\).
LogP and Polarity
Computed XLogP3-AA: \(-0.1\), indicating low lipophilicity and preferential partitioning into aqueous phases relative to nonpolar media. TPSA is 40.5 Å^2; hydrogen-bond donor count = 2 and hydrogen-bond acceptor count = 2. An estimated bioconcentration factor is low, consistent with modest logP and polar character.
Structural Features
The molecule is a flexible, linear pentamethylene chain terminated by two primary alcohol groups (terminal diol). The absence of stereocenters simplifies conformer distributions; rotatable bond count = 4. The dual hydroxyl functionality confers strong hydrogen-bonding capacity, increased viscosity (reported viscosity: \(128\,\mathrm{mPa\cdot s}\) at \(20\,^\circ\mathrm{C}\)), and hygroscopicity. These features make the material useful both as a solvent/co-solvent and as an intermediate for polyester and polyurethane chemistry, where diol functionality is required for condensation polymerizations.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS number: 111-29-5
- EC (EINECS) number: 203-854-4
- UNII: 07UXZ0SCST
- ChEBI: CHEBI:185431
- ChEMBL: CHEMBL448289
- DSSTox Substance ID: DTXSID2041256
Structural identifiers (inline code):
- SMILES: C(CCO)CCO
- InChI: InChI=1S/C5H12O2/c6-4-2-1-3-5-7/h6-7H,1-5H2
- InChIKey: ALQSHHUCVQOPAS-UHFFFAOYSA-N
Synonyms and Structural Names
Common synonyms include: - pentane-1,5-diol - 1,5-pentanediol - 1,5-dihydroxypentane - pentamethylene glycol - 1,5-pentamethylene glycol - alpha,omega-pentanediol - HO(CH2)5OH
(Additional depositor-supplied synonyms and alternate spellings exist for procurement and cataloguing purposes.)
Industrial and Commercial Applications
Representative Uses and Industry Sectors
1,5-Pentanediol is used as a monomer and intermediate in polymer and materials industries: production of polyesters, thermoplastic polyurethanes, plasticizers, resin intermediates, and as an additive for lubricants and brake fluids. Its solvent and humectant properties support applications in cosmetics and personal-care formulations (moisturizers, diluents, preservatives/co-solvents), where it also has reported antimicrobial/antifungal activity and can act as a penetration enhancer in topical formulations. Typical industry sectors include plastics and resin manufacturing, printing-ink production, adhesives, and personal-care product manufacture.
Role in Synthesis or Formulations
As a difunctional primary alcohol it is readily esterified or polymerized to yield diesters, polyesters, and polyurethanes. It is employed as a building block to tune polymer flexibility and glass-transition temperature in linear polyester and polyurethane materials. In formulations, the diol functions as a polar solvent/humectant and as a penetration enhancer for certain active pharmaceutical and cosmetic ingredients; it increases skin retention for some actives while promoting release from vehicle matrices in others.
Safety and Handling Overview
Acute and Occupational Toxicity
Acute oral toxicity values reported include rat LD50 ≈ 2000 mg/kg and mouse/rabbit oral LD50 values reported as 6300 mg/kg in separate reports. Hazard classification summaries note that some notifications list H302 (Harmful if swallowed). Clinical and animal data indicate low-to-moderate systemic toxicity relative to smaller alcohols; effects reported at high doses include central nervous system depression (somnolence, muscle weakness). Patch-testing and controlled human studies show that at low concentrations (e.g., 5%) the compound is generally non‑irritating and non‑sensitizing, although isolated cases of allergic contact dermatitis have been documented. Inhalation exposure is unlikely at ambient temperatures due to low vapor pressure; nevertheless, avoid breathing mists or aerosols.
Combustion and thermal hazards: combustible when heated; autoignition temperature reported as \(635\,^\circ\mathrm{F}\). Thermal decomposition can produce carbon oxides and irritating fumes.
Storage and Handling Considerations
Store in tightly closed containers in a dry, well‑ventilated area; material is hygroscopic. Handle using standard industrial hygiene practices: use chemical-resistant gloves and eye/face protection to prevent repeated or prolonged skin contact; wear impervious clothing when risk of splashes exists. Respiratory protection is typically not required for nuisance exposures; for aerosols or high concentrations use appropriate cartridges/respirators certified to relevant standards. Avoid sources of ignition and contact with strong oxidizers, acylating reagents, and chloroformates. For spills, contain and collect into suitable containers for recovery or disposal; minimize environmental release. For detailed hazard, transport and regulatory information consult the product-specific Safety Data Sheet (SDS) and applicable local legislation.
