Benzaldehyde (100-52-7) Physical and Chemical Properties

Chemical Profile

Benzaldehyde

Benzaldehyde is a simple aromatic aldehyde commonly used as a synthetic intermediate and fragrance/flavor building block in fine chemical and pharmaceutical manufacturing.

CAS Number	100-52-7
Family	Aromatic aldehydes
Typical Form	Colorless to yellow liquid
Common Grades	BP, EP, FCC, JP, Reagent Grade, USP

Employed primarily as an intermediate in the synthesis of dyes, pharmaceuticals and specialty chemicals, benzaldehyde is also specified for fragrance and flavor manufacturing; procurement and R&D teams commonly select grades and purity to suit downstream reactions and formulation requirements.

Benzaldehyde is a simple aromatic aldehyde and the parent compound of the benzaldehyde structural class. Its structure consists of a benzene ring bearing a single formyl substituent; molecular formula \(\ce{C7H6O}\). The carbonyl group is conjugated with the aromatic π-system, which moderates the electrophilicity of the formyl carbon relative to aliphatic aldehydes and strongly influences reactivity (for example, susceptibility to air oxidation and Cannizzaro-type disproportionation under strongly basic, enolization-limited conditions). Electronic delocalization also affects UV/IR absorbance and contributes to the characteristic almond-like odor used industrially in fragrances and flavor formulations.

Physicochemically, benzaldehyde is a volatile, moderately lipophilic liquid with low hydrogen-bonding capacity (H‑bond donor count = 0; H‑bond acceptor count = 1) and a modest partition coefficient (log Kow ≈ 1.48). These attributes produce limited aqueous solubility with significant volatility: it readily dissolves in common organic solvents (alcohols, ethers, oils), is miscible with ethanol, and evaporates from aqueous media on environmental release. As an aldehyde, it oxidizes in air to benzoic acid and may form peroxides or other oxidation products on prolonged exposure to oxygen and light; it is also reactive toward strong oxidants and peroxyacids and undergoes base- or acid-catalyzed condensations and redox transformations characteristic of aldehydes in synthesis.

Common commercial grades reported for this substance include: BP, EP, FCC, JP, Reagent Grade, USP.

Basic Physical Properties

Density

Reported liquid densities: 1.046 at 68 \(\mathrm{°F}\); 1.050 at 15 \(\mathrm{°C}\)/4 \(\mathrm{°C}\); relative density (water = 1) 1.05; range 1.040–1.047.
Practical implication: liquid benzaldehyde is slightly denser than water and will sink in aqueous spills; this affects containment and remediation strategies.

Melting Point

Reported values: -15 \(\mathrm{°F}\); -57.12 \(\mathrm{°C}\); -26 \(\mathrm{°C}\).
Freezing point also listed as -56.9 \(\mathrm{°C}\).
Practical implication: the compound is a liquid under standard ambient and typical refrigerated storage conditions.

Boiling Point

Reported values: 354 \(\mathrm{°F}\) at 760 mmHg; 178.7 \(\mathrm{°C}\); 179 \(\mathrm{°C}\).
Reduced-pressure data: 62.00 to 63.00 \(\mathrm{°C}\) @ 10.00 mmHg.
Practical implication: normal-pressure boiling occurs near 179 \(\mathrm{°C}\); lower-temperature distillation under vacuum is commonly used for purification.

Vapor Pressure

Reported values (multiple conditions): 1 mmHg at 79.2 \(\mathrm{°F}\); 5 mmHg at 122.2 \(\mathrm{°F}\); 10 mmHg at 144 \(\mathrm{°F}\).
Additional reported figures: 0.12 mmHg (unspecified condition); 1.27 mmHg at 25 \(\mathrm{°C}\); vapor pressure expressed as 133 Pa at 26 \(\mathrm{°C}\).
Practical implication: vapor pressures indicate appreciable volatility at ambient and elevated temperatures; engineering controls should limit inhalation exposure and vapor accumulation.

Flash Point

Reported values: 148 \(\mathrm{°F}\); 145 \(\mathrm{°F}\) / 63 \(\mathrm{°C}\) (closed cup); 73.9 \(\mathrm{°C}\) (open cup); 63 \(\mathrm{°C}\) c.c.
Flammable/combustible behavior: lower flammable limit reported as 1.4% by volume.
Practical implication: benzaldehyde is combustible; storage and handling should follow standard precautions for combustible organic liquids and avoid ignition sources.

Chemical Properties

Solubility and Phase Behavior

Reported aqueous solubility values: "less than 0.1 mg/mL at 67.1 \(\mathrm{°F}\)"; "In water, 6950 mg/L at 25 \(\mathrm{°C}\)"; "Approximately 0.6% wt. at 20 \(\mathrm{°C}\)"; alternative listing "6.95 mg/mL at 25 \(\mathrm{°C}\)".
Miscibility/solvent behavior: miscible with alcohols (e.g., ethanol), soluble in ethers and many organic solvents and oils; soluble in liquid ammonia. Water content in benzaldehyde at 20 \(\mathrm{°C}\) reported as 1.5 wt%.
Practical interpretation: reports show variability in expressed units; values equivalent to ≈6.95 g/L (6950 mg/L) indicate limited but measurable aqueous solubility. The compound is readily soluble in organic media and commonly used as a solvent for resins and oils.

Reactivity and Stability

Functional group: aromatic aldehyde (formyl on benzene). Reactivity profile includes:
Air oxidation to the corresponding carboxylic acid (benzoic acid) on exposure to oxygen/light.
Susceptibility to peroxide formation under particular conditions; care for time‑sensitive peroxide-forming chemicals is advised.
Under strong base and absence of α-hydrogen (the formyl carbon has no α‑H for enolization), benzaldehyde undergoes disproportionation (Cannizzaro reaction) rather than aldol condensations.
Violent or exothermic reactions reported with strong oxidizing agents and peroxyacids; incompatibilities include strong oxidizers, strong bases, alkali metals, and certain metals (iron, aluminum) or reactive organics.
Stability/shelf life: generally stable under recommended storage (cool, dark, tightly closed). Tendency to yellow on prolonged storage due to oxidation products; recommended storage under inert atmosphere for long-term purity.

Thermodynamic Data

Standard Enthalpies and Heat Capacity

Standard enthalpy of formation (liquid): -87.0 kJ/mol.
Molar heat capacity at 298.15 K (liquid): 172.0 J/mol·K.
Heat of vaporization: 42.5 kJ/mol at 179.0 \(\mathrm{°C}\).
Heat of combustion: -3525.0 kJ/mol.
Practical implication: the thermochemical data support typical energy demands for vaporization/distillation and combustion hazard assessments.

Molecular Parameters

Molecular Weight and Formula

Molecular formula: \(\ce{C7H6O}\).
Molecular weight: 106.12.
Exact/monoisotopic mass: 106.041864811.
Heavy atom count: 8.
Compound is neutral (formal charge 0).

LogP and Polarity

Computed XLogP: 1.5.
Experimental/estimated log Kow: 1.48.
Topological polar surface area (TPSA): 17.1 Å^2.
Hydrogen-bonding counts: H‑bond donors = 0; H‑bond acceptors = 1; rotatable bond count = 1.
Practical interpretation: moderate lipophilicity with low polar surface area and minimal H‑bonding capability explains relatively low aqueous solubility, low bioconcentration potential, and ready passage into organic phases.

Structural Features

Structural summary: an aromatic ring (benzene) directly substituted with a formyl group (–CHO). The formyl hydrogen renders the carbonyl susceptible to oxidation and to nucleophilic addition reactions typical of aldehydes. Conjugation with the aromatic ring reduces carbonyl reactivity relative to unconjugated aliphatic aldehydes.
Key synthetic transformations: hydrogenation of the carbonyl gives benzyl alcohol (a major industrial derivative); oxidation yields benzoic acid; under strongly basic, α‑hydrogen‑absent conditions, benzaldehyde undergoes Cannizzaro disproportionation to afford benzyl alcohol and benzoate species.

Identifiers and Synonyms

Registry Numbers and Codes

CAS Registry Number: 100-52-7
EC number / Catalogue identifier: 202-860-4 (as reported)
UN number (transport): 1990 (as reported)
Other registry codes reported: FEMA Number 2127; UNII TA269SD04T; ChEBI CHEBI:17169; ChEMBL CHEMBL15972

Synonyms and Structural Names

Common synonyms (reported): benzaldehyde; phenylmethanal; benzoic aldehyde; benzene carbaldehyde; benzene carboxaldehyde; benzenemethylal; bitter almond oil (synthetic).
Structural descriptors and registry strings:
SMILES: C1=CC=C(C=C1)C=O
InChI: InChI=1S/C7H6O/c8-6-7-4-2-1-3-5-7/h1-6H
InChIKey: HUMNYLRZRPPJDN-UHFFFAOYSA-N

Industrial and Commercial Applications

Representative Uses and Industry Sectors

Principal uses: flavoring and fragrance ingredient in perfumery and food flavorings; chemical intermediate in the production of dyes and pharmaceutical intermediates; solvent for resins and oils; precursor for hydrogenation to benzyl alcohol. A substantial fraction of production is allocated to fragrance/flavor applications and as an intermediate for further chemical manufacture.
Market/production notes: manufactured industrially by partial oxidation of toluene and by hydrolysis of benzal chloride; available in multiple commercial purity grades for technical, perfumery, and pharmaceutical use.
Regulatory/use constraints: industry fragrance/flavor guidance implements category-specific maximum concentrations for finished products (examples of reported limits include 0.045% for lip products, 0.014% for products applied to the axillae, 0.27% for fingertip-applied face/body products, 0.15% for products with oral exposure). Such concentration limits are used in product formulation to manage sensitization and systemic exposure risks.

Role in Synthesis or Formulations

Synthetic roles: versatile electrophilic aldehyde used in nucleophilic addition chemistry, reductive transformations (hydrogenation to benzyl alcohol), and as a building block for substituted aromatics. It is also used as a solvent or co-solvent for resins, oils and in formulation matrices where aromatic character and volatility are required.
Formulation considerations: compatibility with alcohols and organic solvents; susceptibility to oxidation requires antioxidant measures or inert‑atmosphere storage for high-purity grades destined for flavor or pharmaceutical use.

Safety and Handling Overview

Acute and Occupational Toxicity

Routes of exposure: inhalation, dermal contact, ingestion; systemic absorption occurs via skin and lungs. Metabolic fate includes rapid oxidation to benzoic acid and subsequent conjugation (e.g., hippuric acid) with renal excretion.
Key toxicological metrics and effects (reported): oral LD50 (rat) values ≈ 1300–1430 mg/kg; dermal LD50 (rabbit) > 1250 mg/kg. Acute inhalation data indicate potential respiratory irritation at high concentrations. Reported hazard statements (expressed as standard hazard categories in practice) include acute toxicity (harmful if swallowed or inhaled), skin and eye irritation, potential skin sensitization (allergic contact dermatitis), and central nervous system effects (drowsiness/dizziness) at sufficiently high exposures. Chronic or repeated exposures have produced systemic effects in high-dose animal studies; some evidence of tumorigenicity was observed in long-term studies in mice but not in rats (study-level details are part of toxicology reports).
Occupational exposure guideline (reported): example workplace guideline reported as 8‑hr TWA ≈ 2 ppm and STEL ≈ 4 ppm (where pertinent local occupational exposure limits apply, consult regulatory guidance and product-specific safety documentation).

Storage and Handling Considerations

Storage: store in a cool, dry, well-ventilated area away from strong oxidizers and bases; protect from light and air to minimize oxidation; inert-gas blanketing (e.g., nitrogen) is advisable for long-term storage of high-purity material. Keep containers tightly closed and upright to prevent leakage.
Handling: use in well-ventilated areas or with local exhaust; eliminate ignition sources; control static accumulation; use appropriate grounding/bonding when transferring large volumes.
Personal protective equipment: eye/face protection, chemical-resistant gloves, and protective clothing; where inhalation risk exists, use appropriate respiratory protection as determined by exposure assessment (air‑purifying cartridges for organic vapors or supplied-air respirators in high‑concentration or emergency situations).
Fire and spill response: suitable extinguishing media include water spray, alcohol‑resistant foam, dry chemical or CO2; vapors are heavier than air and can travel to ignition sources. For spills, contain and collect using inert absorbents and prevent entry to drains and waterways; for environmental releases note the compound’s mobility and volatility.
Regulatory/transport notes: combustible liquid; transport identifiers reported include UN 1990 (as an organic compound) and classification as combustible/flammable under shipping regulations where applicable. For detailed hazard, transport and regulatory information, users should refer to the product-specific Safety Data Sheet (SDS) and local legislation.

For further specification or analytical requirements (assay grade, impurity profile, packaging and storage grade selection), product‑specific technical data and the supplier’s certificate of analysis should be consulted.