2-Methyl-1-pentanol (105-30-6) Physical and Chemical Properties
2-Methyl-1-pentanol
Branched C6 primary alcohol used industrially as a solvent and synthetic intermediate, with limited water solubility and good compatibility with common organic solvents.
| CAS Number | 105-30-6 |
| Family | Aliphatic primary alcohols |
| Typical Form | Colorless liquid |
| Common Grades | EP, JP, USP |
2‑Methyl‑1‑pentanol is a primary aliphatic alcohol (IUPAC: 2‑methylpentan‑1‑ol) in the C6 alcohol class. Structurally it is a branched hexanol isomer with a methyl substituent at C‑2 and a primary hydroxyl group at C‑1; the connectivity is concisely represented by SMILES: CCCC(C)CO. The molecule combines a nonpolar hydrocarbon backbone (six carbons, multiple rotatable C–C bonds) with a single polar functional group (–OH), giving amphiphilic behavior typical of small, branched primary alcohols. The topological polar surface area (TPSA) is 20.2, and the compound has one hydrogen‑bond donor and one acceptor site, consistent with limited but definite hydrogen‑bonding capacity.
Electronically the hydroxyl group is the dominant reactive site: it confers weak Brønsted acidity (typical of aliphatic alcohols), nucleophilicity of the oxygen lone pairs, and the ability to form hydrogen bonds with protic solvents. The branched alkyl chain reduces molecular packing and intermolecular hydrogen‑bonding density relative to linear isomers, lowering volatility compared with the straight‑chain analogue (1‑pentanol) while maintaining moderate lipophilicity (XLogP ≈ 1.8). Oxidation of the primary alcohol gives the corresponding aldehyde (2‑methylvaleraldehyde) and, under stronger oxidative conditions, the carboxylic acid; hydrolysis is not a relevant pathway for the intact alcohol under ambient conditions.
Commercially, 2‑methyl‑1‑pentanol is used as an industrial solvent and an intermediate in organic synthesis (see Applications section). Common commercial grades reported for this substance include: EP, JP, USP.
Basic Physical Properties
Density
Reported density: 0.8263 @ 20 °C/4 °C. This value indicates a bulk liquid density substantially lower than water, consistent with a hydrocarbon‑dominant composition and moderate molecular mass.
Melting Point
No experimentally established value for this property is available in the current data context.
Boiling Point
Reported boiling point: 148 °C @ 760 MM HG. The relatively high normal boiling point for a six‑carbon alcohol reflects the presence of the hydroxyl group and associated hydrogen bonding; branching at C‑2 reduces the boiling point slightly relative to linear isomers of similar molar mass.
Vapor Pressure
Experimental vapor pressure values reported include: 1.92 mm Hg (at 25 °C, from experimentally‑derived coefficients) and 1.1 mm Hg (at 20 °C). These low mm Hg values indicate modest volatility at ambient temperature; branching contributes to reduced vapor pressure relative to less branched C6 alcohols.
Flash Point
Reported flash points: 54 °C (129 °F); closed cup specified in one report. The flash point places the material in a combustible to flammable category for handling and storage considerations; vapors can form flammable mixtures with air under suitable conditions.
Chemical Properties
Solubility and Phase Behavior
Solubility notes reported: soluble in alcohol, ether, and acetone. Water solubility entries include "0.31% by weight in water" and "Water solubility = 6000 mg/L @ 25 °C." The combination of a single polar –OH group with a hydrophobic C6 skeleton yields appreciable but limited water miscibility; the measured solubility in water (\(6000\,\mathrm{mg}\,\mathrm{L}^{-1}\) at 25 °C) is consistent with moderate aqueous solubility and ready miscibility with many polar organic solvents.
Phase behavior: the compound is a colorless liquid at ambient conditions and will partition preferentially into organic phases; vapor‑phase presence is expected in the atmosphere based on the reported vapor pressure.
Reactivity and Stability
2‑Methyl‑1‑pentanol is chemically stable toward mild conditions but can undergo the standard reactions of primary alcohols: oxidation (to aldehyde/carboxylic acid), esterification with acids/acid derivatives, and substitution under strong activating conditions. It is not expected to hydrolyze (no hydrolyzable functional groups beyond the alcohol). Thermal stability is typical for small primary alcohols; reported autoignition temperature: 590 °F (310 °C). Avoid strong oxidizers and strong acids/bases that can catalyze dehydration or charring; containers should be kept away from heat and ignition sources.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
No experimentally established value for this property is available in the current data context.
Molecular Parameters
Molecular Weight and Formula
Molecular formula: C6H14O. Molecular weight: 102.17.
LogP and Polarity
Computed XLogP3 (XLogP3‑AA): 1.8. Topological polar surface area (TPSA): 20.2. Hydrogen bond donors: 1. Hydrogen bond acceptors: 1. These descriptors indicate moderate lipophilicity with limited polar surface area, consistent with a small branched primary alcohol that partitions between aqueous and organic phases but favors organic media.
Structural Features
Canonical SMILES: CCCC(C)CO. InChI: InChI=1S/C6H14O/c1-3-4-6(2)5-7/h6-7H,3-5H2,1-2H3. InChIKey: PFNHSEQQEPMLNI-UHFFFAOYSA-N. The molecule has three rotatable bonds reported and one undefined stereocenter count of 1 (racemic mixture or unspecified stereochemistry may be present in some samples). Branching at C‑2 reduces chain flexibility slightly relative to linear isomers, lowers volatility, and modulates solvent properties such as solvency power and viscosity influence when used as an extender.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS Number: 105-30-6
- Deprecated CAS: 17092-54-5
- European Community (EC) Number: 203-285-1
- UNII: U8933MB30H
- ChEMBL ID: CHEMBL1569610
- DSSTox Substance ID: DTXSID9026714
- Metabolomics Workbench ID: 123653
- Nikkaji Number: J49.947A
- NSC Number: 6250
- InChIKey: PFNHSEQQEPMLNI-UHFFFAOYSA-N
- SMILES: CCCC(C)CO
Synonyms and Structural Names
Depositor‑supplied synonyms include (selection): 2‑METHYL‑1‑PENTANOL; 2‑Methylpentan‑1‑ol; 1‑Pentanol, 2‑methyl‑; sec‑Amyl carbinol; Amyl methyl alcohol; Isohexyl alcohol; 2‑Methylpentanol; 2‑Methyl‑1‑pentanol (±); 2‑Propylpropanol; 2‑methylpentyl alcohol. (Multiple additional variant names and legacy identifiers exist and are used in supplier and regulatory contexts.)
Industrial and Commercial Applications
Representative Uses and Industry Sectors
2‑Methyl‑1‑pentanol is used industrially as a solvent and as a solvent extender/solution viscosity reducer. It is employed as an organic intermediate in the manufacture of other compounds, including intermediates for plastics and specialty chemicals. Production volumes have been reported at industrial scale historically, reflecting utility in solvent and intermediate roles.
Role in Synthesis or Formulations
The primary alcohol functionality makes 2‑methyl‑1‑pentanol a useful building block for oxidation (to aldehyde/carboxylic acid), esterification (to produce esters with characteristic solvent/odor properties), and etherification reactions. Its branching confers lower evaporation rates and reduced volatility compared with straight‑chain amyl alcohols, making it useful where slower evaporation or lower vapor pressure is desired in formulations.
Safety and Handling Overview
Acute and Occupational Toxicity
Hazard classifications reported for this substance include flammable liquid and vapor (classification variants reported), acute oral toxicity (categories indicating harmful if swallowed), skin and eye irritation/damage potential, and possible respiratory irritation on sufficient exposure. Representative toxicological values reported include: - Oral LD50 (rat): \(1.41\,\mathrm{g}\,\mathrm{kg}^{-1}\). - Dermal LD50 (rabbit): \(3.56\,\mathrm{g}\,\mathrm{kg}^{-1}\). - Inhalation: LC (rat) > 5,000 ppm (6 h) reported for mixed primary isomers.
Clinical and animal data indicate the substance can be an irritant to skin, eyes, nose and throat and may produce central nervous system effects typical of solvent exposure (dizziness, narcosis) at high concentrations. Appropriate occupational controls (ventilation, exposure monitoring) are warranted during manufacture and use.
Storage and Handling Considerations
Store in a cool, well‑ventilated area away from heat and ignition sources. Keep containers tightly closed and inspect periodically; isolate from incompatible materials such as strong oxidizers and strong acids/bases. Use grounding and bonding during transfers to reduce electrostatic hazards. For handling, use appropriate personal protective equipment (chemical‑resistant gloves, eye/face protection, and suitable respiratory protection where vapor concentrations may exceed occupational limits). In the event of release, eliminate ignition sources, ventilate, and manage vapors that are heavier than air and may accumulate in low areas. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
