acetaldehyde

Acetaldehyde identity evidence

Record the reference identity and observations supporting or contradicting assignment to acetaldehyde.

1. Which identifier and structural reference anchor this material to acetaldehyde? definition
2. What analytical evidence distinguishes it from ethanol, acetic acid and other aldehydes? measurement

Represented acetaldehyde fraction

Declare whether the record concerns monomer, a formulated material or an operationally defined analytical quantity.

1. Does this record describe neat acetaldehyde, a solution, a vapour mixture or a trace constituent? boundary
2. Does the reported amount include acetaldehyde released from other species during analysis, and how is that distinguished from initially present monomer? definition

Content on an explicit basis

Associate each amount with its matrix, units, uncertainty and relevant impurities.

1. What acetaldehyde concentration or purity was measured, on which mass, volume or gas basis? measurement
2. Which solvent, water content, additives or co-occurring carbonyls affect the intended interpretation? boundary

Representative acetaldehyde result

Require method suitability and evidence addressing losses or changes during sampling and preparation.

1. What sampling, sealing, preservation and elapsed-time records support the result? provenance
2. How were selectivity, recovery, calibration, detection limits and possible preparation-induced acetaldehyde formation assessed? measurement

Condition-qualified phase

Record phase observations with measured conditions and distinguish observation from prediction.

1. What temperature, absolute pressure and phase were observed at the stated time? measurement
2. If phase behaviour is predicted, what composition-specific evidence supports using that prediction? provenance

Containment condition

Link acetaldehyde condition to closure integrity, headspace observations and transfer history.

1. What evidence describes closure integrity, headspace pressure and any acetaldehyde loss or release? measurement
2. Which verified containment and temperature requirements must hold before the proposed transfer? action

Transformation indicators

Record relevant analytical changes without inferring stability from appearance alone.

1. What measurements indicate changes in acetaldehyde content, acidity, peroxide content or transformation products? measurement
2. Which suspected change remains unconfirmed, and what evidence would distinguish the competing explanations? boundary

Storage validity

Assess whether documented conditions remain compatible with the particular acetaldehyde material.

1. What stabilization, opening dates, air exposure and temperature excursions are documented? provenance
2. Has contact with incompatible materials or a storage deviation triggered a product-specific reassessment requirement? action

Applicable hazard controls

Require applicable safety evidence and verified controls before treating an operation as permissible.

1. Which current product safety document and jurisdiction-specific exposure criteria apply to this form and use? provenance
2. What evidence confirms adequate ignition control, containment and exposure control for the proposed operation? action

Acetaldehyde use authorization

Tie acceptance, restriction or quarantine to a named specification and responsible decision.

1. Does the measured identity, composition and stability satisfy the requirements of the named use? action
2. What missing evidence or subsequent change requires withholding use, quarantine or renewed assessment? action

Kinds and varieties

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Technical/industrial acetaldehyde (bulk chemical, typically ≥99%)
• High-purity/reagent acetaldehyde
• Stabilized (polymerization-inhibited) versus uninhibited liquid
• Aqueous acetaldehyde solutions (a common handling form)
• Food/flavour-grade acetaldehyde (FEMA 2003)
• Free versus sulfite-bound acetaldehyde in wine, beer and spirits
• Endogenous metabolic acetaldehyde (ethanol → alcohol dehydrogenase → acetaldehyde)
• Ambient and indoor-air acetaldehyde as a volatile organic compound

1. Which of these kinds and varieties hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Identifiers and schemes

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• CAS Registry Number - 75-07-0 - Primary chemical identity for regulation, transport and inventory listings.
• EC / EINECS - 200-836-8 - EU inventory number; CLP Index 605-003-00-6.
• IUPAC name - ethanal - Systematic name; industry and OSHA/EPA texts still use acetaldehyde.
• UN number - UN 1089 - Dangerous-goods identity; Class 3, Packing Group I.
• PubChem CID - 177 - NCBI compound record.
• ChEBI - CHEBI:15343 - Ontology identifier used in metabolic pathway databases.
• InChIKey - IKEHLMZTGIFGAA-UHFFFAOYSA-N - Structure hash for the parent molecule.
• HS / CN code - 2912.12 - Harmonized System heading for acetaldehyde as such.
• FEMA - 2003 - Flavouring-substance number.
• Wikidata - Q31550 - Catalogue item for the chemical species.

1. Which of these identifiers and schemes hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Standards and regulation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• IARC/WHO Monographs: acetaldehyde Group 2B as a chemical; acetaldehyde associated with consumption of alcoholic beverages Group 1 (Vol. 100E).
• OSHA 29 CFR 1910.1000 Table Z-1: PEL 200 ppm (360 mg·m⁻³) 8-hour TWA.
• ACGIH TLVs: ceiling value 25 ppm (widely cited occupational benchmark, tighter than the OSHA PEL).
• EU CLP Regulation (EC) No 1272/2008, Index 605-003-00-6: harmonised classification including Flam. Liq. 1 and carcinogenicity/mutagenicity entries; REACH (EC) 1907/2006 registered substance.
• UN Model Regulations / ADR/RID/IMDG: UN 1089, Class 3, Packing Group I.
• US EPA Clean Air Act: listed Hazardous Air Pollutant.
• California Proposition 65 (OEHHA): listed carcinogen.
• FDA flavouring framework and FEMA GRAS (FEMA 2003); JECFA flavouring evaluations for acetaldehyde as a food flavour.

1. Which of these standards and regulation hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Real-world use

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Feedstock for pentaerythritol (alkyd resins, coatings, PETN pathway) and for pyridine/alkylpyridine bases.
• Historical and residual route to acetic acid and acetate esters; largely displaced by methanol carbonylation for acetic acid.
• Flavour constituent (green-apple / bruised-apple note) added at low milligram-per-kilogram levels, and formed in situ in wine, beer, cider and spirits.
• Human metabolite of beverage ethanol; the species responsible for alcohol flush when ALDH2 is deficient.
• Ambient and indoor VOC from combustion, tobacco smoke, vehicle exhaust and photochemical oxidation of VOCs.
• Laboratory reagent and calibration standard; stored cold because it boils near room temperature.

1. Which of these real-world use hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Typical measurements

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Normal boiling point - 20.1-20.4 - °C
• Melting point - −123.5 - °C
• Density at 20 °C - 0.780-0.785 - g·cm⁻³
• Closed-cup flash point - about −39 - °C
• Autoignition temperature - 140-185 - °C
• Explosive limits in air - 4-57 - vol%
• Commercial purity - ≥99-99.5 - wt%
• Free acetaldehyde in still wine - typically 10-80; oxidation fault often >100-125 - mg·L⁻¹
• Occupational air concentration (order of limit values) - 25 (ceiling) to 200 (PEL TWA) - ppm v/v
• Peripheral blood acetaldehyde after ethanol - <5 with functional ALDH2; tens of µmol·L⁻¹ with ALDH2 deficiency - µmol·L⁻¹

1. Which of these typical measurements hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Failure modes and hazards

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Extremely flammable vapour; flashback and vapour-cloud explosion. Explosive range in air is wide (~4-57 vol%).
• Unusually low autoignition temperature, so hot surfaces that would not ignite many solvents can ignite acetaldehyde.
• Acid-catalysed polymerization to paraldehyde (trimer) or metaldehyde (tetramer), with heat and drum/cylinder overpressure.
• Boils near ambient temperature: container overpressure unless refrigerated or kept under pressure-rated closures.
• Air oxidation toward acetic acid and peroxidic species; incompatibility with strong acids, bases, oxidizers and amines (exothermic condensations).
• Acute irritation of eyes and respiratory tract; high concentrations can cause pulmonary oedema.
• Genotoxicity and carcinogenicity, amplified when ALDH2 detoxification is slow (alcohol flush, East-Asian ALDH2*2).
• Sensory fault in wine and beer (bruised apple, sherry-like oxidation) when free acetaldehyde rises.

1. Which of these failure modes and hazards hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Regional variation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Dual naming: IUPAC/EU labels use ethanal; North American industry, OSHA and EPA texts use acetaldehyde.
• Enology: French and OIV texts often say éthanal; New World cellar practice says acetaldehyde, and "aldehyde" in a tasting note usually means this compound.
• ALDH2*2 (Glu504Lys) is common in East Asia, so population exposure to metabolic acetaldehyde after drinking is a clinical and public-health issue there in a way it is not in Europe or Africa.
• Occupational limits diverge: OSHA PEL 200 ppm TWA versus ACGIH ceiling 25 ppm and generally tighter EU national OELs; some German MAK treatment treats it as a carcinogen rather than a simple irritant.
• Production route: ethylene Wacker oxidation dominates in OECD plants; acetylene hydration persisted longer in coal-chemistry regions of China and the former Eastern bloc.

1. Which of these regional variation hold for the sense of acetaldehyde this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• formaldehyde (methanal) - C₁ versus C₂ aldehyde; bp about −19 °C versus +20 °C; chromotropic-acid or DNPH-HPLC retention time separates them.
• acetone - Ketone, not aldehyde: Tollens and Fehling tests are negative for acetone and positive for acetaldehyde; ¹H NMR shows no aldehydic proton near 9.8 ppm.
• ethylene oxide - Constitutional isomer (also C₂H₄O) but an epoxide: no carbonyl IR, no aldehydic ¹H; transported as UN 1040, not UN 1089.
• ethanol - The reduction product/precursor; no carbonyl stretch; GC retention and bp 78 °C versus 20 °C.
• acetic acid - The two-electron oxidation product; acidic aqueous pH and a carboxylic IR pattern versus aldehyde C-H stretch near 2720 cm⁻¹.
• propanal - Next homologue; GC-MS parent/fragments (m/z 58 versus 44) and longer GC retention distinguish it.
• paraldehyde - Cyclic trimer sold as a separate drug/solvent; bp ~124 °C and no free carbonyl until acid-catalysed depolymerization back to acetaldehyde.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of acetaldehyde this model covers, and on what evidence? provenance