aniline
Enable an AI agent to recognise aniline, assess the identity, condition and suitability of a particular quantity, and determine which handling or use decisions require further evidence.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise aniline, assess the identity, condition and suitability of a particular quantity, and determine which handling or use decisions require further evidence.
Aniline (benzenamine, C6H5NH2) is the parent aromatic primary amine in which an amino group is bonded directly to a benzene ring; it is a weakly basic, oily, colourless-to-brown liquid that is the industrial precursor to methylene diphenyl diisocyanate, rubber-processing chemicals, dyes, and many agrochemicals.
It can be Reconcile an aniline label and supplier record with analytical identity evidence.; Compare aniline assay, water content and impurity results against a named use specification.; Investigate colour, clarity or phase changes using storage history and targeted analytical evidence.; Assess whether a proposed transfer or storage arrangement has documented aniline compatibility and exposure controls.; Assign or revise a use-specific acceptance, hold or rejection decision.; Link aniline material to its mixture, reaction, exposure incident or waste record when the decision extends beyond this model..
Distinguishing features
Structural evidence identifies an amino group directly attached to an otherwise unsubstituted benzene ring, distinguishing aniline from benzylamine.
Identity evidence supports C6H7N and the parent compound C6H5NH2, distinguishing it from ring-substituted anilines.
Composition and speciation evidence distinguish neutral aniline from an anilinium salt with an associated counterion.
A substance identifier such as CAS 62-53-3 agrees with the container record and analytical identity evidence; a matching name alone is insufficient.
A mixture containing aniline is distinguished from an aniline material lot by recording the other constituents and the basis of its reported aniline content.
Scope
+ Aniline identity and evidence distinguishing it from related aromatic compounds
+ Composition, purity and impurities of aniline material
+ Physical condition and changes during storage or handling
+ Aniline-specific exposure, containment and compatibility considerations
+ Suitability of a particular quantity for an identified use
- Anilinium salts as separately identified chemical substances
- Substituted anilines such as toluidines and chloroanilines
- Whole mixtures and formulations containing aniline
- Manufacturing plants, reaction procedures and process control systems
- Clinical diagnosis and treatment of exposed people
- Downstream dyes, polymers and other products made using aniline
Characteristics
- Chemical identity evidence
- Links to structure, identifiers and analytical identification records Prevents related amines, salts or incorrectly labelled material from being treated as aniline.
- Chemical form
- Neutral aniline; aniline-containing mixture; anilinium salt; unresolved Determines whether this model directly applies or must refer to a neighbouring substance or mixture model.
- Aniline assay
- Mass fraction or another explicitly stated analytical basis, with method and uncertainty Supports use-specific acceptance without confusing chromatographic area percentage with mass purity.
- Water content
- mg/kg or mass %, with analytical method and sampling date May affect aniline's suitability for a particular reaction or material specification.
- Impurity profile
- Identified constituents, measured concentrations, detection limits and unresolved analytical signals Allows acceptance decisions to account for specific contaminants rather than total assay alone.
- Observed phase
- Liquid; solid; mixed phase; unresolved, at recorded temperature Makes physical observations interpretable and helps distinguish temperature effects from unexpected material changes.
- Colour and clarity
- Named colour scale or documented visual observation, with clarity and observation conditions Supports detection of changes while avoiding the assumption that colour alone establishes identity or purity.
- Storage exposure history
- Records of temperature, light, atmosphere, moisture exposure and container opening Provides context for investigating changes in aniline condition and deciding whether to retest.
- Containment condition
- Intact; suspected leak; confirmed leak; compatibility unresolved Connects the material's condition to whether handling can proceed under the applicable controls.
- Intended-use disposition
- Unassessed; accepted for named use; held pending evidence; rejected for named use Keeps suitability specific to an application, specification and evidence date.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 5 bundles · 9 layers · 16 findings · 24 questions.
Aniline identity and boundaries Establishes whether the material is the parent aromatic amine aniline and identifies when a neighbouring model is required.
Confusing aniline with a substituted amine, salt or formulation changes the meaning of its properties and possible uses.
Molecular identity
Connects the claimed aniline identity to structural and analytical evidence.
Parent aromatic amine
The model must capture evidence for an amino group directly attached to an unsubstituted benzene ring.
- Does the assigned structure identify C6H5NH2 rather than benzylamine or a substituted aniline? definition
- Which analytical record supports the aniline identity of this material, beyond its label or supplier name? provenance
Chemical form and material boundary
Separates aniline substance identity from salts and multicomponent materials.
Free base, salt or mixture
The model must identify the chemical form and distinguish a lot of aniline from a separately modelled salt or mixture.
- Is the material described as neutral aniline, an anilinium salt or an aniline-containing mixture, and what supports that assignment? boundary
- Do counterions, solvents or intentionally added constituents require a linked salt or mixture model? boundary
Aniline composition and use fitness Connects measured composition to the requirements of an identified application.
An aniline purity claim does not by itself establish acceptable water content, impurity levels or suitability for a particular use.
Assay and impurity evidence
Captures what composition measurements establish and what remains unresolved.
Interpretable aniline composition
The model must distinguish aniline assay, water measurements and impurity results, including their analytical bases.
- What is the measured aniline content, and is it reported as mass fraction, chromatographic area percentage or another basis? measurement
- What water content, identified impurities and unresolved signals were measured, with which methods and detection limits? measurement
Application-specific acceptance
Relates the material's composition to a named reaction, formulation or other use.
Fitness for named use
Acceptance must refer to explicit requirements for the intended use of aniline.
- Which aniline assay, water, colour and impurity limits apply to the intended use, and where are those limits specified? provenance
- Do the available results justify acceptance for that use, or is additional testing or a hold required? action
Aniline condition and storage history Tracks physical observations and exposure history needed to interpret changes in stored aniline.
Colour, clarity and phase observations require context and cannot independently establish deterioration or continued suitability.
Physical condition
Records observable condition under specified measurement conditions.
Phase, colour and clarity
The model must retain temperature and observation conditions alongside appearance changes.
- What phase, colour, clarity and visible foreign material are observed at the recorded temperature? measurement
- How do these observations compare with the lot's earlier measurements or applicable aniline specification? measurement
Exposure and reassessment
Uses storage and handling history to determine what condition evidence needs renewal.
History-informed retesting
The model must connect possible changes to documented exposure without assigning an unverified chemical cause.
- What air, light, moisture and temperature exposure is documented since the last representative analysis? provenance
- Which observed changes or gaps in history require new aniline assay, water or impurity measurements before the intended use? action
Aniline handling and compatibility Connects aniline hazard evidence and material compatibility to a proposed handling operation.
A decision to handle aniline requires evidence about exposure routes and the actual contact materials and co-present substances.
Exposure control evidence
Records the authoritative hazard information and controls relevant to the material and operation.
Operation-specific exposure assessment
The model must link the proposed operation to documented aniline exposure hazards, including evidence concerning skin uptake and methemoglobinemia.
- Which authoritative sources establish the exposure routes and health hazards applicable to this aniline material, including skin uptake and methemoglobinemia? provenance
- Does the proposed operation have documented controls addressing those routes, or must it remain on hold pending an assessment? action
Contact materials and co-present substances
Assesses the actual containment system and substances aniline may contact.
Supported contact conditions
The model must distinguish evidenced compatibility from assumptions about containers, seals, transfer equipment and nearby chemicals.
- What evidence supports compatibility of aniline with the proposed container, seals and transfer equipment at the intended temperature and contact duration? provenance
- Could contact with acids, oxidising substances or other co-present materials change aniline's form or introduce a reaction hazard requiring a separate assessment? boundary
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Technical / industrial aniline (typical 99.0-99.9 % assay, often containing nitrobenzene, cyclohexylamine, and water as process impurities)
- High-purity / reagent-grade aniline (ACS or equivalent, typically ≥99.5 %)
- Aniline hydrochloride (the crystalline salt used as a solid handling form and in some dye and pharmaceutical processes)
- Aniline oil (historical trade name for crude or mixed aniline fractions from coal-tar or nitrobenzene reduction)
- Substituted anilines as a chemical class (o-, m-, p-toluidine, chloroanilines, nitroanilines, etc., treated as distinct substances in regulation and commerce)
- Which of these kinds and varieties hold for the sense of aniline 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 - 62-53-3 - Parent free base; aniline hydrochloride is 142-04-1.
- EC / EINECS - 200-539-3 - European Community number used in REACH and CLP.
- IUPAC name - aniline (preferred); also benzenamine - IUPAC also accepts phenylamine as a retained name in some contexts.
- PubChem CID - 6115 - NCBI PubChem compound identifier.
- Wikidata - Q186414 - Wikidata item for aniline.
- InChIKey - PAYRUJLWNCNPSJ-UHFFFAOYSA-N - Standard InChIKey for C6H5NH2.
- UN number (transport) - UN 1547 - Aniline; packing group II, toxic liquid. Aniline hydrochloride is UN 1548.
- HS / CN tariff - 2921.41 (aniline and its salts) - Harmonized System heading for aniline and salts; EU CN further splits 2921 41 00.
- RTECS - BW6650000 - NIOSH Registry of Toxic Effects of Chemical Substances number.
- Which of these identifiers and schemes hold for the sense of aniline 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 Monographs Vol. 127 (2021): aniline classified Group 2A, probably carcinogenic to humans (IARC/WHO).
- EU CLP Regulation (EC) No 1272/2008, Annex VI: harmonised classification including Acute Tox. 3 (oral, dermal, inhalation), Skin Sens. 1, Eye Dam. 1, Muta. 2, Carc. 2, STOT RE 1, Aquatic Acute 1 / Aquatic Chronic 1 (ECHA).
- REACH Regulation (EC) No 1907/2006: fully registered substance, EC 200-539-3; subject to authorisation/restriction screening as a CMR and environmental hazard (ECHA).
- OSHA PELs / NIOSH RELs / ACGIH TLVs: occupational exposure limits for aniline (skin notation; methemoglobin-forming aromatic amine) (OSHA, NIOSH, ACGIH).
- UN Model Regulations / ADR / IMDG / IATA: UN 1547, Class 6.1 toxic liquid (UNECE, IMO, IATA).
- US EPA: listed hazardous substance under CERCLA; reportable quantity 5,000 lb (40 CFR 302); also a TRI-listed chemical (EPA).
- ASTM / ISO industrial specifications exist for aniline assay and impurity limits used in MDI and dye manufacture (industry purchase specs more common than a single public ISO product standard).
- Which of these standards and regulation hold for the sense of aniline 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.
- Largest current use is as feedstock for methylene diphenyl diisocyanate (MDI) via condensation with formaldehyde to MDA then phosgenation; MDI goes into polyurethane foams, elastomers, and coatings.
- Intermediate for rubber-processing chemicals (antioxidants, antiozonants such as 6PPD via p-aminodiphenylamine routes).
- Historical and continuing dye intermediate: azo dyes, indigo-related processes, and aniline black; also pharmaceuticals (acetanilide-derived drugs historically; still a building block).
- Agrochemical intermediate (herbicides and fungicides built on the aniline nucleus).
- Laboratory reagent and specialty chemical; aniline hydrochloride as a solid salt in some dye and pharmaceutical recipes.
- Encountered as a workplace chemical in nitrobenzene hydrogenation plants, MDI trains, and as a contaminant/metabolite concern in aromatic-amine exposure monitoring (urinary p-aminophenol, methemoglobin).
- Which of these real-world use hold for the sense of aniline 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.
- Assay (purity of commercial aniline) - 99.0-99.9 (industrial); ≥99.5 (reagent) - mass %
- Melting / freezing point - -6.2 to -6.0 - °C
- Normal boiling point - 184-184.4 - °C
- Density (20 °C) - 1.021-1.022 - g·cm⁻³
- Vapour pressure (25 °C) - about 40-90 (order of 0.7 hPa / ~0.5 mmHg class) - Pa
- pKa of conjugate acid (anilinium, water, 25 °C) - 4.6-4.63 - pKa units
- Flash point (closed cup) - 70-76 - °C
- Occupational exposure (air) - typical OELs around 2-8 mg·m⁻³ (jurisdiction-dependent); biological monitoring via methemoglobin and urinary metabolites - mg·m⁻³
- Water solubility (25 °C) - about 36 - g·L⁻¹
- Which of these typical measurements hold for the sense of aniline 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.
- Acute methaemoglobinaemia after inhalation, dermal absorption, or ingestion; cyanosis, headache, and hypoxic injury; skin absorption is a major route (hence skin notations on OELs).
- Probable human carcinogen (IARC 2A); associated with bladder and other sites in aromatic-amine epidemiology, with aniline itself re-evaluated as probably carcinogenic.
- Germ-cell mutagenicity concern (EU Muta. 2) and repeated-dose haemolytic / splenic toxicity (STOT RE 1).
- Strong skin sensitiser and severe eye damage (corrosive to eyes).
- Very toxic to aquatic life with long-lasting effects; spills to watercourses are a primary environmental failure mode.
- Combustible liquid: vapour can form explosive mixtures above the flash point; fire produces NOx and toxic smoke.
- Darkens and resinifies on air/light exposure (oxidation to azobenzene, phenazine-type tars); quality failure in storage if not inerted or inhibited.
- Process hazard in manufacture: nitrobenzene hydrogenation and MDI/phosgene trains carry fire, toxicity, and runaway risks; aniline leaks are both toxic and odour-noticeable but odour is not a reliable warning.
- Which of these failure modes and hazards hold for the sense of aniline 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.
- English/chemical literature uses aniline (IUPAC retained) and benzenamine; older texts use phenylamine or aminobenzene.
- German industry and regulation use Anilin; French aniline; the historical trade name 'aniline oil' persists in some dye and coal-tar contexts.
- Occupational limits and carcinogen listings differ: IARC Group 2A globally vs EU CLP Carc. 2; US OSHA PEL is older and higher than many current NIOSH/ACGIH/EU values.
- China, India, and the EU are the main production/use regions for MDI-chain aniline; coal-tar aniline is largely historical in OECD countries but the dye-industry vocabulary remains in South Asia.
- Transport: UN 1547 is universal, but domestic proper shipping names and packing instructions vary slightly (ADR vs 49 CFR vs IMDG).
- Which of these regional variation hold for the sense of aniline 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.
- Nitrobenzene - Immediate industrial precursor (C6H5NO2). Distinguishes by IR/NMR (NO2 vs NH2), much lower basicity, characteristic almond-like odour, and CAS 98-95-3; GC retention and MS molecular ion 123 vs 93.
- Cyclohexylamine - Saturated analogue and a common process impurity from over-hydrogenation. Distinguishes by much higher basicity (pKa of conjugate acid ~10.6 vs ~4.6), lack of aromatic UV band near 230-280 nm, and MS/NMR aliphatic pattern.
- Toluidines (o-, m-, p-methylaniline) - Methyl-substituted anilines, separate CAS numbers (e.g. 95-53-4 for o-toluidine, IARC 1). Distinguishes by extra methyl in NMR/MS (M⁺ 107 vs 93) and chromatographic separation; o-toluidine is a known human bladder carcinogen.
- Aniline hydrochloride - Salt, not the free base: solid, water-soluble, CAS 142-04-1, UN 1548. Distinguishes by melting point (~198 °C with decomposition vs liquid free base), chloride test, and non-volatile solid handling.
- Phenol - Isosteric C6H5OH vs C6H5NH2. Distinguishes by acidity (phenol pKa ~10) vs aniline basicity, FeCl3 colour test for phenol, and different IR (O-H vs N-H).
- N-methylaniline / N,N-dimethylaniline - N-alkylated anilines used in dyes and as intermediates. Distinguishes by missing N-H (for DMA), extra N-methyl NMR signals, and different CAS/toxicity profiles (DMA is also a listed aromatic amine).
- Benzylamine - C6H5CH2NH2, an aliphatic amine attached to an aromatic ring rather than an aromatic amine. Distinguishes by much higher basicity (pKa ~9.3), different NMR (benzylic CH2), and not a methaemoglobin former of the same class.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of aniline this model covers, and on what evidence? provenance
Sources
- Aniline, Compound Summary (CID 6115) - IUPAC name, molecular formula, identifiers (CAS, InChI, SMILES), physical properties, toxicity summary, and GHS classification.
- Aniline (C6H7N) - NIST Chemistry WebBook, SRD 69 - Evaluated melting/boiling points, density, vapour pressure, thermochemical data, and CAS RN 62-53-3.
- IARC Monographs Volume 127: Some Aromatic Amines and Related Compounds - Aniline - Carcinogenicity evaluation (Group 2A, probably carcinogenic to humans), industrial production routes, and principal uses (MDI, rubber chemicals, dyes).
- Aniline - ECHA Substance Infocard / REACH registration (EC 200-539-3) - EU CLP classification, REACH registration, occupational exposure, and restriction context for aniline as a harmonised-classified substance.
What the second pass must settle
- Which authoritative identity references and analytical methods should establish the minimum evidence for distinguishing aniline from related amines in this registry?
- Which impurities and acceptance limits matter for the intended applications, and how should commercial aniline grade names map to those requirements?
- Which storage-related colour or composition changes reliably justify retesting, and which remain inconclusive without further analysis?
- Which current authoritative hazard and compatibility sources cover the actual aniline grade, contact materials and operating conditions?
- What evidence should determine whether a particular material is represented as an aniline lot with impurities or as a separately modelled aniline-containing mixture?