Definition
3‑Methyl‑1‑pentanol (IUPAC name: 3‑methylpentan‑1‑ol) is a branched, six‑carbon primary alcohol with the molecular formula C₆H₁₄O. It is one of the several structural isomers of hexanol and is sometimes referred to by the trivial name isohexanol.
Overview
3‑Methyl‑1‑pentanol is a colorless liquid at ambient temperature. It is moderately soluble in water (approximately 7 % w/w at 20 °C) and miscible with many organic solvents such as ethanol, ether, and chloroform. The compound exhibits a characteristic pleasant odor and is used in the flavor and fragrance industry as a taste and scent modifier. In laboratory practice, it serves as a solvent and as an intermediate in organic synthesis, for example in the preparation of esters, ethers, and other functionalized derivatives.
Typical physical data (as reported in standard chemical reference works) are:
- Molar mass: 102.18 g mol⁻¹
- Density: 0.82 g cm⁻³ (20 °C)
- Boiling point: 158–159 °C (at 1 atm)
- Flash point: 44 °C (closed cup)
The compound is classified as a primary alcohol because the hydroxyl (‑OH) group is attached to a primary carbon atom (C‑1 of the pentyl chain). The presence of a methyl substituent at the third carbon introduces branching, which influences both physical properties and reactivity relative to the straight‑chain hexan‑1‑ol isomer.
Etymology / Origin
The systematic name “3‑methylpentan‑1‑ol” follows IUPAC nomenclature rules: the parent hydrocarbon is pentane, a five‑carbon chain; a methyl group is attached to the third carbon atom, and a hydroxyl functional group is attached to the first carbon. The trivial name “isohexanol” denotes that the molecule is an isomer of hexanol with a branched structure (“iso‑” indicating a methyl branch on the main chain).
Characteristics
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Chemical reactivity: As a primary alcohol, 3‑methyl‑1‑pentanol readily undergoes oxidation to the corresponding aldehyde (3‑methylpentanal) and further to the carboxylic acid (3‑methylpentanoic acid) using typical oxidizing agents (e.g., PCC, Jones reagent). It also participates in esterification reactions with carboxylic acids or acid anhydrides to give the corresponding esters, which are valued for their fruity aromas.
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Synthesis: Commercially, 3‑methyl‑1‑pentanol can be prepared by catalytic hydrogenation of 3‑methyl‑1‑pentanal or by reduction of the same aldehyde with sodium borohydride or lithium aluminum hydride. An alternative laboratory route involves the Grignard reaction of isobutylmagnesium bromide with acetaldehyde, followed by acidic work‑up.
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Safety and handling: The compound is flammable and may cause skin and eye irritation. Recommended handling includes the use of appropriate personal protective equipment (gloves, goggles) and storage in a cool, well‑ventilated area away from ignition sources.
Related Topics
- Primary alcohols – organic compounds containing a −OH group attached to a primary carbon.
- Hexanol isomers – includes 1‑hexanol, 2‑hexanol, 3‑hexanol, and branched isomers such as 2‑methyl‑1‑pentanol and 4‑methyl‑1‑pentanol.
- Flavor and fragrance chemistry – the use of short‑chain branched alcohols as aroma compounds.
- Organic oxidation reactions – methods for converting primary alcohols to aldehydes and acids.
- Grignard reagents – organomagnesium halides employed in carbon–carbon bond formation, relevant to the synthesis of branched alcohols.