benzene
Enable an AI agent to recognise benzene, assess the identity and condition of a particular quantity, and determine which handling, use or disposition actions are supported by 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 benzene, assess the identity and condition of a particular quantity, and determine which handling, use or disposition actions are supported by evidence.
A planar C6H6 arene whose six equivalent carbons each contribute one 2p electron to a fully delocalized π sextet; it is the parent aromatic hydrocarbon, recovered from petroleum reforming and coal carbonization and handled as a restricted industrial intermediate rather than a general-purpose solvent.
It can be Reconcile labels, supplier documents and analytical results to establish or challenge benzene identity.; Assess a benzene quantity against a named purity or intended-use specification.; Request further sampling or analysis when identity, contamination or composition evidence is insufficient.; Evaluate a proposed transfer, storage or use against documented containment, compatibility and exposure controls.; Flag a suspected release or exposure concern and route it to the applicable response procedure.; Assign an evidence-supported disposition such as accepted use, quarantine, return or waste management..
Distinguishing features
Require evidence of the unsubstituted six-carbon aromatic ring with molecular formula C6H6; the formula alone does not establish benzene identity.
Distinguish benzene from petroleum benzine by checking the chemical identity and composition record rather than treating similar names as synonyms.
Distinguish benzene from toluene and other substituted aromatics using analytical evidence capable of resolving those compounds.
Distinguish benzene from cyclohexane using molecular or analytical identity evidence; a six-membered carbon ring alone is insufficient.
Distinguish a quantity represented as benzene from a mixture containing benzene by recording its composition, reporting basis and applicable material specification.
Scope
+ Benzene identity and evidence distinguishing it from similarly named substances and other hydrocarbons
+ Purity, impurities and confidence that a particular quantity qualifies as benzene
+ Physical state and measured properties under recorded conditions
+ Containment, vapour release and contamination status of a benzene quantity
+ Evidence supporting or restricting use, transfer, storage and disposition
- Complete composition and performance models for gasoline, petroleum benzine and other benzene-containing mixtures
- Separate chemical models for toluene, cyclohexane and substituted benzene compounds
- Plant design and operating models for benzene production or consumption
- Clinical diagnosis and treatment of exposed people
- Facility-wide ventilation, fire protection and environmental remediation systems
Characteristics
- Chemical identity
- Benzene; molecular formula C6H6; structural identity and referenced identifiers Prevents similar names, formulas or ring structures from being accepted as proof of identity.
- Identity evidence status
- Label-only | document-supported | analytically supported | conflicting | unknown Determines how confidently an agent may apply benzene-specific decisions to the quantity.
- Benzene content
- Mass fraction, mole fraction or another explicitly stated basis, with method and uncertainty Separates identity claims from measured composition and supports acceptance against a named specification.
- Impurity profile
- Named impurities and concentrations, with units, detection limits and sampling date Water, other hydrocarbons and process contaminants may change suitability or invalidate a purity claim.
- Physical phase
- Solid | liquid | vapour | multiple phases | unknown, at recorded temperature and pressure A benzene quantity cannot be assessed from an assumed liquid state alone.
- Material temperature
- °C or K, with measurement location and time Supports interpretation of phase, volatility and the validity of property measurements.
- Containment pressure
- kPa, explicitly absolute or gauge, with measurement location and time Provides context for phase behaviour and containment decisions.
- Quantity
- kg or mol; volume permitted with temperature and conversion basis Supports inventory, transfer reconciliation and assessment of the scale of a release.
- Containment and release status
- Closed and verified | opened under controls | suspected leak | confirmed release | unknown Distinguishes a controlled inventory item from a quantity requiring a release response.
- Associated airborne benzene measurement
- Link to an air sample or monitor record including concentration, units, location, time and averaging period Connects the material to relevant exposure evidence without treating ambient concentration as an intrinsic substance property.
- Intended-use specification
- Referenced specification and version, with acceptance status A benzene grade suitable for one use may not satisfy another use's analytical or process requirements.
- Applicable hazard and control basis
- Referenced safety data, local assessment and applicable requirements with dates and jurisdiction Makes decisions about benzene's health and fire hazards traceable to the requirements actually governing the action.
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 · 27 questions.
Benzene identity and material boundary Establishes whether the represented material is benzene and where this model's ownership ends.
Confusing benzene with benzine, another ring compound or a benzene-containing mixture would attach the wrong material identity to subsequent decisions.
Molecular and naming identity
Connects the benzene name to a supported chemical identity.
Identity evidence and conflicts
Records what supports the unsubstituted aromatic C6H6 identity and whether labels, documents or analyses disagree.
- What structural identity distinguishes this material from cyclohexane, substituted aromatics and other substances sharing a formula or similar name? definition
- Which label, supplier record or analytical result supports benzene identity, and are any of those records in conflict? provenance
Substance versus mixture
Determines whether the quantity is represented as benzene or belongs to a neighbouring mixture model.
Benzene content and representation
Records the composition evidence and classification basis without inventing a universal purity threshold.
- What benzene content was measured or declared, on what basis and with what uncertainty? measurement
- Under the applicable material specification, is this quantity benzene with impurities or a mixture that should link to benzene as a constituent? boundary
Benzene grade and condition Describes composition and physical condition relevant to the actual quantity and intended use.
The benzene identity alone does not establish purity, current phase or fitness for a particular analytical or industrial use.
Purity and contamination
Assesses declared grade against measured impurities and the quantity's history.
Grade support and impurity gaps
Captures evidence for the claimed grade, including water, other hydrocarbons and contaminants relevant to the intended use.
- Which impurities were measured, with what concentrations and detection limits, and which relevant impurities were not assessed? measurement
- Does the certificate or sample represent this quantity after its latest transfer, opening or potential contamination event? provenance
- Does the available composition evidence support the intended-use specification, or is further analysis required? action
Phase and thermal condition
Records observed phase and the conditions needed to interpret it.
Observed phase and property consistency
Assesses whether phase and measured physical properties are consistent with the claimed benzene composition under recorded conditions.
- What phase or phases are present at the measured material temperature and pressure? measurement
- Are observed phase behaviour or physical properties inconsistent with the claimed composition, and what uncertainty prevents interpreting the discrepancy? boundary
Benzene containment and release Connects the benzene quantity to its containment and evidence of movement into surrounding air or other media.
Benzene assessment must account for vapour and loss of containment as well as the material remaining in its vessel.
Vessel and transfer interface
Records the containment interfaces relevant to a proposed benzene operation.
Containment fitness for benzene
Links vessel, closure, seal and transfer-path evidence to the conditions of the proposed operation.
- What evidence establishes compatibility of benzene with the wetted materials and closures at the proposed temperature and duration? provenance
- Do the documented containment and transfer controls support the proposed operation, or does an unresolved condition require holding it? action
Vapour and material loss
Tracks evidence of benzene outside its intended containment without assuming the source of every detection.
Release evidence and source attribution
Records leaks, inventory discrepancies and environmental detections with their uncertainty and attribution.
- What direct observations, inventory changes or benzene measurements indicate a release, and when and where were they obtained? measurement
- What evidence links the detected benzene to this quantity rather than another source, and where does the environmental or incident model take ownership? boundary
Benzene action constraints and disposition Determines which proposed actions are supported by the applicable hazard, exposure and material-quality evidence.
A decision about benzene requires both material fitness and documented controls addressing its health and fire hazards.
Hazard and exposure decision basis
Connects benzene-specific hazards to the controls and measurements governing the proposed activity.
Applicable controls and evidence
Records the authoritative basis for health, ignition and exposure constraints while keeping personal medical assessment outside this model.
- Which current safety data and applicable requirements establish the controls for benzene's carcinogenicity, other health hazards and flammability in this activity? provenance
- What task-relevant exposure measurements are available, including sampling location, duration, units and method limitations? measurement
- Does the documented control assessment support this proposed activity, and which missing evidence or failed condition requires escalation? action
Use acceptance and disposition
Assigns a supported next step to the actual benzene quantity.
Supported next action
Connects identity confidence, grade, contamination and control status to an accountable disposition.
- Do identity, composition and condition evidence satisfy the named requirements for the intended use? boundary
- Should this quantity be accepted, held for analysis, quarantined, returned or routed to waste management, and what evidence and authority support that decision? action
- Which change in composition, containment, intended use or governing requirements would require the decision to be reviewed? action
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.
- petroleum-derived benzene
- coal-tar / coke-oven benzene
- industrial-grade benzene
- nitration-grade benzene
- thiophene-free / reagent-grade benzene
- ASTM refined benzene-535
- crude benzol (mixed BTX distillate)
- gasoline-contained benzene (blendstock component, not a product grade)
- Which of these kinds and varieties hold for the sense of benzene 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 - 71-43-2 - Primary substance identifier used by OSHA, ECHA and most inventories; several deprecated CAS numbers exist for the same compound.
- PubChem CID - 241 - NCBI compound record for C6H6.
- ChEBI - CHEBI:16716 - Ontology class for the parent arene; secondary IDs include CHEBI:3025, CHEBI:13876, CHEBI:22703, CHEBI:41187.
- EC / EINECS - 200-753-7 - European Community inventory number.
- InChIKey - UHOVQNZJYSORNB-UHFFFAOYSA-N - Standard hashed InChI for unsubstituted benzene.
- UN number - UN 1114 - Dangerous-goods identifier for liquid benzene.
- FDA UNII - J64922108F - FDA Substance Registration System.
- EPA DSSTox - DTXSID3039242 - CompTox substance identifier.
- ICSC - 0015 - ILO International Chemical Safety Card number.
- KEGG COMPOUND - C01407 - Pathway/metabolite identifier.
- HMDB - HMDB0001505 - Human Metabolome Database.
- molecular formula - C6H6 - IUPAC name is simply benzene.
- Which of these identifiers and schemes hold for the sense of benzene 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.
- OSHA 29 CFR 1910.1028 (US Department of Labor): occupational benzene standard; 1 ppm 8-hour TWA PEL and 5 ppm 15-minute STEL, with a partial exemption for gasoline after wholesale storage.
- OSHA 29 CFR 1910.106 / 1910.309 (US Department of Labor): Class IB flammable liquid; locations with ignitable benzene vapor treated as Class I Group D.
- US EPA mobile-source gasoline benzene limits (as reported by the American Cancer Society): 0.62% by volume annual average, 1.3% maximum.
- US EPA Safe Drinking Water Act MCL 5 ppb (µg/L) for benzene in drinking water; FDA matching 5 ppb limit in bottled water.
- IARC (WHO): Group 1, carcinogenic to humans, on sufficient evidence for acute myeloid leukemia.
- US NTP Report on Carcinogens: known to be a human carcinogen.
- ASTM International D2359: Standard Specification for Refined Benzene-535 (current edition D2359-24).
- UN Recommendations on the Transport of Dangerous Goods: UN 1114, Class 3 flammable liquid.
- Which of these standards and regulation hold for the sense of benzene 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.
- Almost all commercial benzene is a petrochemical building block, not a sold-through solvent: historically about half goes to ethylbenzene/styrene, about a fifth to cumene/phenol, and about a tenth to cyclohexane for nylon intermediates, with smaller cuts to nitrobenzene/aniline, detergent alkylate and chlorobenzenes.
- It is present in crude oil and is produced as a by-product of catalytic reforming and of coal carbonization; coke-oven benzole remains a distinct supply stream.
- Finished motor gasoline still carries residual benzene under a volume cap; indoor retail dispensing for more than four hours per day is an OSHA-covered exposure.
- Laboratory and ASTM reagent grades (including thiophene-free material) are used where sulfur poisons catalysts or where a defined freezing point is required.
- Highest workplace concentrations occur in primary production and in liquid transfer between tanks and containers.
- Which of these real-world use hold for the sense of benzene 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.
- molar mass - 78.11-78.12 - g·mol⁻¹
- melting / solidification point - 5.35 (ASTM 535 minimum, anhydrous) to ~5.6 - °C
- normal boiling point - 80.1 - °C
- liquid density near 20-25 °C - 0.874-0.879 - g·cm⁻³
- flash point (closed-cup class) - −11 - °C
- autoignition temperature - 498 - °C
- water solubility at 25 °C - ~1.8 - g·L⁻¹
- vapor density relative to air - ~2.8 - dimensionless
- occupational air concentration (OSHA PEL / STEL) - 1 (8 h TWA) / 5 (15 min) - ppm
- drinking-water MCL (US EPA / FDA) - 5 - µg·L⁻¹
- gasoline benzene content (US EPA annual average / cap) - 0.62 / 1.3 - % by volume
- refined benzene-535 purity (purchase spec) - ≥99.8 - wt %
- Which of these typical measurements hold for the sense of benzene 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.
- Highly flammable Class IB liquid whose vapor is heavier than air; OSHA treats airborne concentrations above 3,250 ppm as a fire/explosion hazard and requires bonding, grounding and non-sparking tools on transfer.
- Chronic inhalation causes bone-marrow toxicity and is causally linked to acute myeloid leukemia (IARC Group 1; NTP known human carcinogen).
- Acute high exposure depresses the central nervous system; liquid transfer and poorly ventilated indoor fuel dispensing are the typical high-dose settings.
- Slight water solubility plus density below 1 means spilled product floats and still partitions into groundwater at concentrations above the 5 µg/L drinking-water MCL.
- Thiophene and other organic sulfur in coal-derived grades foul hydrogenation and alkylation catalysts, which is why nitration-grade and thiophene-free cuts are specified.
- Historic use as a general solvent is a legacy exposure pathway; current law treats that use as a controlled carcinogen, not a commodity cleaner.
- Which of these failure modes and hazards hold for the sense of benzene 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.
- In several European languages benzine/benzin names light petroleum spirit, not C6H6; the arene is benzène (French), Benzeen (Dutch), Benzen (Polish) or historically Benzol (German), which is why English 'benzine' is treated as an obsolete and misleading synonym.
- US OSHA still permits 1 ppm as an 8-hour PEL, while ACGIH lists a tighter 0.5 ppm TLV for the same air contaminant.
- Some US states set drinking-water limits below the federal 5 µg/L MCL.
- Post-Soviet product standards split petroleum benzene (GOST 9572) from coal/shale benzene (GOST 8448) and grade them as highly purified, for synthesis, or for nitration, a source-based taxonomy still used in that trade even though ASTM D2359 is the usual Western purchase spec.
- Gasoline benzene is a regulated residual in the US at 0.62% vol annual average; the occupational standard then largely steps aside once fuel has left wholesale storage, which is not how pure-benzene plants are regulated.
- Which of these regional variation hold for the sense of benzene 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.
- toluene - C7H8 with a methyl substituent; boiling point ~111 °C versus ~80 °C, and ¹H NMR shows a methyl singlet near 2.3 ppm that benzene lacks.
- cyclohexane - Saturated C6H12 analogue with nearly the same boiling point (~81 °C) but density ~0.78 g·cm⁻³ versus ~0.88, aliphatic rather than aromatic ¹H NMR, and no electrophilic aromatic substitution.
- benzine / petroleum ether - A boiling-range mixture of aliphatic naphtha, not a single C6H6 compound; identity is a distillation cut, not CAS 71-43-2.
- crude benzol / benzol 90 - A BTX-rich coke-oven distillate (classically ~80-85% benzene with toluene and xylene), not refined benzene-535.
- thiophene - The sulfur heterocycle that rides with coal-tar benzene; it is quantified by ASTM D1685/D4735/D7011 because it is the impurity that defines thiophene-free grade.
- ethylbenzene and the xylenes - BTX co-products from reforming; they separate from benzene by GC retention or by boiling point (all well above 80 °C) rather than by the C6 aromatic ring test itself.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of benzene this model covers, and on what evidence? provenance
Sources
- Benzene, Compound Summary for CID 241 - Molecular identity (C6H6), CAS 71-43-2, PubChem CID 241, InChI/InChIKey/SMILES, EC 200-753-7, UN 1114, UNII, ICSC, DSSTox and related registry numbers, and the description as a clear, highly flammable aromatic liquid found in crude oil and refining streams.
- CHEBI:16716 - benzene - Specialist definition as a six-carbon aromatic annulene with a delocalized π system; ChEBI, KEGG and HMDB identifiers; average mass; and the industrial-solvent / carcinogen framing.
- 29 CFR 1910.1028 - Benzene - US occupational scope (CAS 71-43-2), 8-hour PEL of 1 ppm and 15-minute STEL of 5 ppm, regulated-area definition, and the gasoline-dispensing exception.
- 29 CFR 1910.1028 Appendix B - Substance Technical Guidelines, Benzene - Synonyms, Class IB flammable-liquid classification, 3,250 ppm fire/explosion threshold, Class I Group D electrical classification, and high-exposure transfer operations.
- Benzene and Cancer Risk - IARC Group 1 (AML) and NTP known-human-carcinogen classifications; EPA gasoline benzene cap (0.62% vol annual average, 1.3% max); drinking-water and bottled-water limits of 5 ppb.
- Hazardous Substances Data Bank (HSDB): 35 - Benzene - Downstream use split (ethylbenzene/styrene, cumene/phenol, cyclohexane, nitrobenzene/aniline, detergent alkylate); industrial vs nitration vs thiophene-free grades; and historic benzol-90 composition.
- ASTM D2359-24 Standard Specification for Refined Benzene-535 - The named commercial grade refined benzene-535 and the existence of an ASTM purchase specification for high-purity benzene.
- Benzene - Thermophysical Properties - Melting and boiling points, liquid density, flash and autoignition temperatures, water solubility, vapor density relative to air, log Kow, and critical constants.
What the second pass must settle
- Does an existing Vercy world model already own benzene or provide a chemical-substance model that this registry entry must reference?
- Which authoritative identity references and analytical methods should establish benzene identity for the intended applications, and what are their limitations?
- Which grade specifications and impurity limits govern the intended uses, including the boundary between benzene with impurities and a benzene-containing mixture?
- Which validated property and compatibility references cover the temperatures, pressures and containment materials expected in deployment?
- Which jurisdictions and operational contexts must be supported for exposure, storage, transport and waste decisions, and how will those requirements be kept current?