2'-Hydroxyacetophenone (118-93-4) Physical and Chemical Properties
2'-Hydroxyacetophenone
Aromatic phenolic ketone commonly used as a flavor/fragrance intermediate and analytical standard, relevant to synthesis, formulation and QC workflows.
| CAS Number | 118-93-4 |
| Family | Aromatic ketones |
| Typical Form | Colorless to light yellow liquid |
| Common Grades | BP, EP, JP, Reagent Grade |
2'-Hydroxyacetophenone is an ortho‑hydroxy substituted aromatic ketone of the acetophenone family; systematic name 1-(2‑hydroxyphenyl)ethanone. Structurally it comprises a monosubstituted benzene ring bearing an acetyl group (aryl methyl ketone) adjacent to a phenolic OH. The proximate arrangement of the carbonyl and phenolic substituents promotes a strong intramolecular hydrogen bond that influences spectroscopic signatures (notably a highly deshielded phenolic proton) and modulates volatility and solvation behaviour relative to non‑hydrogen‑bonding analogues.
Electronic properties combine a moderate lipophilic aryl core with a single polar substituent set (one hydrogen‑bond donor, two hydrogen‑bond acceptors). The compound is neutral under typical conditions and does not carry a formal charge. The phenolic OH confers weak acidity (deprotonation under basic conditions) and enables hydrogen‑bonding interactions in condensed phases; the acetyl group withdraws electron density by resonance/inductive effects, affecting reactivity toward electrophilic aromatic substitution. Hydrolysis under neutral conditions is not expected; oxidative conversion of the phenol under strongly oxidizing conditions and reduction of the ketone under strongly reducing conditions are the principal chemical transformations to consider.
The combination of modest polar surface area and measured partitioning parameters produces moderate lipophilicity with limited aqueous solubility but good solubility in organic solvents and fats; these attributes explain its use in flavor and fragrance contexts and its role as a minor human metabolite of related methoxyacetophenones. Common commercial grades reported for this substance include: BP, EP, JP, Reagent Grade.
Basic Physical Properties
Density
Experimental values are reported as 1.127-1.133 (units not specified in the available data). This range is consistent with an aromatic ketone containing a polar OH group, which typically yields densities near or above unity in undetermined reporting units.
Melting Point
Reported melting point: \(4\)–\(6\,^\circ\mathrm{C}\). A melting range in this region indicates the substance will be liquid at ordinary ambient temperatures above approximately \(6\,^\circ\mathrm{C}\), consistent with experimental descriptions of a colorless to light‑yellow liquid.
Boiling Point
Reported boiling point: \(213.00\,^\circ\mathrm{C}\) at \(717.00\,\mathrm{mmHg}\). The relatively high boiling temperature at reduced pressure is consistent with a low vapor pressure and indicates a substantially higher boiling point at standard atmospheric pressure (pressure dependence typical for aromatic ketones).
Vapor Pressure
Reported vapor pressure: \(0.00748\,\mathrm{mmHg}\). The low vapor pressure is consistent with the high boiling point and with handling considerations for low volatility liquids.
Flash Point
No experimentally established value for this property is available in the current data context.
Chemical Properties
Solubility and Phase Behavior
Solubility descriptors indicate the compound is "slightly soluble in water; soluble in fat" and "miscible (in ethanol)". These qualitative solubility statements align with measured partition coefficients (see LogP data): the polar phenolic OH provides some aqueous affinity and hydrogen‑bonding capability, but the hydrophobic aryl and acetyl moieties dominate, producing limited water solubility and good solubility in alcohols and lipophilic media. In formulations, ethanol and other polar organic solvents give complete miscibility; nonpolar matrices (oils, fats) will dissolve the compound readily.
Reactivity and Stability
As an ortho‑hydroxyaryl methyl ketone, 2'-hydroxyacetophenone undergoes class‑typical reactivity: the phenolic OH can be deprotonated under basic conditions and will participate in hydrogen bonding and esterification or etherification reactions under suitable activating conditions. The ortho relationship of OH and C=O supports intramolecular hydrogen bonding, which stabilizes particular conformers and affects the OH chemical shift and proton exchange behavior. The carbonyl group is susceptible to standard ketone reactions (reduction to the secondary alcohol, nucleophilic additions under activation); the aromatic ring is less activated toward electrophilic substitution because of the electron‑withdrawing character of the acyl substituent, although the phenolic substituent locally increases reactivity at adjacent positions. The substance is generally stable under neutral and ambient conditions but will oxidize under strong oxidizing environments; hydrolytic cleavage is not a primary degradation route under normal conditions.
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: \(\mathrm{C}_8\mathrm{H}_8\mathrm{O}_2\).
Molecular weight: \(136.15\).
Exact/monoisotopic mass: \(136.052429494\).
LogP and Polarity
Computed/descriptive partitioning and polarity metrics include XLogP3 = \(1.9\) and reported LogP = \(1.92\). Topological polar surface area (TPSA) = \(37.3\). Hydrogen‑bond counts: H‑bond donor = \(1\); H‑bond acceptor = \(2\). Rotatable bond count = \(1\). These values indicate moderate lipophilicity with limited polar surface area, consistent with modest membrane permeability and restricted aqueous solubility.
Structural Features
Canonical SMILES: CC(=O)C1=CC=CC=C1O
Standard InChI: InChI=1S/C8H8O2/c1-6(9)7-4-2-3-5-8(7)10/h2-5,10H,1H3
Standard InChIKey: JECYUBVRTQDVAT-UHFFFAOYSA-N
The structure is a monosubstituted benzene bearing an ortho‑hydroxy group and an acetyl substituent; intramolecular O–H···O=C hydrogen bonding is sterically favorable and is reflected in spectroscopic data (notably a strongly deshielded phenolic proton). The singular rotatable bond relates to the methyl–carbonyl link and ring orientation; molecular complexity is moderate for a low‑molecular‑weight aromatic ketone.
Identifiers and Synonyms
Registry Numbers and Codes
- CAS Number: 118-93-4
- EC Number: 204-288-0
- UNII: 3E533Z76W0
- FEMA Number: 3548
- InChIKey: JECYUBVRTQDVAT-UHFFFAOYSA-N
- InChI: InChI=1S/C8H8O2/c1-6(9)7-4-2-3-5-8(7)10/h2-5,10H,1H3
- SMILES: CC(=O)C1=CC=CC=C1O
- ChEBI: CHEBI:145716
- ChEMBL: CHEMBL3187012
Synonyms and Structural Names
Common synonyms appearing in supplier and regulatory annotations include: 2'-Hydroxyacetophenone; 2‑acetylphenol; o‑hydroxyacetophenone; 1-(2‑hydroxyphenyl)ethanone; o‑acetylphenol. It is also listed in some contexts as a flavoring substance and as an impurity designation in acetaminophen/paracetamol manufacturing (Paracetamol Impurity I).
Industrial and Commercial Applications
Representative Uses and Industry Sectors
The substance is used as a flavoring and fragrance ingredient, providing floral and herbaceous notes in formulations; it is registered for such functional use in food‑flavoring inventories. Production volumes reported in manufacturing summaries indicate industrial activity at scales below one million pounds per year in aggregated reporting years. It is also encountered as a minor human metabolite of related substituted acetophenones.
Role in Synthesis or Formulations
In chemical manufacturing and formulation contexts, 2'-hydroxyacetophenone functions as a flavour/fragrance intermediate and analytical standard. It can serve as a synthetic building block in organic synthesis for elaboration of substituted phenolic and heterocyclic compounds. It is also noted as an identifiable impurity in certain pharmaceutical preparations (e.g., paracetamol-related impurity lists) and is therefore relevant to quality control and impurity profiling workflows.
Safety and Handling Overview
Acute and Occupational Toxicity
Aggregated hazard notifications report GHS hazard statements including: H302 (Harmful if swallowed) — \(10.4\%\); H315 (Causes skin irritation) — \(19.9\%\); H319 (Causes serious eye irritation) — \(19.9\%\); H335 (May cause respiratory irritation) — \(19.5\%\). Toxicity summary entries list an intraperitoneal LD50 (mouse) of \(100\,\mathrm{mg}\,\mathrm{kg}^{-1}\) (intraperitoneal, mouse) and document skin and eye irritation potential up to corrosive effects in severe exposures. Occupational exposure may cause skin, eye and respiratory irritation; appropriate controls and personal protective equipment are recommended.
Storage and Handling Considerations
Handle using standard industrial hygiene controls for irritant phenolic ketones: minimize direct skin and eye contact, avoid inhalation of vapors or mists, and employ gloves, eye protection and adequate local exhaust ventilation. Store containers tightly closed in a cool, well‑ventilated area away from strong oxidizing agents and strong bases; segregation from reactive oxidizers is prudent. Because the substance is a low‑volatility liquid at ambient temperatures, spill control focuses on absorption and containment rather than vapor suppression. For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and applicable local legislation.
