The cyclohexane CAS number is 110-82-7. This unique numerical identifier, assigned by the Chemical Abstracts Service, distinguishes cyclohexane from all other chemical substances worldwide.
CAS numbers are standardized identifiers used globally in scientific literature, regulatory databases, and industrial safety records. For cyclohexane, the number 110-82-7 appears in every official document involving its handling, storage, or transport. The format follows a three-part structure: the first segment (110) identifies the specific compound, the second (82) acts as a checksum, and the final digit (7) confirms validity. This system prevents confusion between structurally similar compounds such as methylcyclohexane or cyclohexene.
When citing cyclohexane in research, regulatory submissions, or material safety data sheets (MSDS), using the CAS number ensures precision. A single digit error can lead to misidentification, especially in automated systems. For example, entering 110-82-6 instead of 110-82-7 would reference a different substance entirely.
CAS numbers are generated by the American Chemical Society's Chemical Abstracts Service. Each number is unique and permanent. Once assigned, it never changes-even if the compound's name or structure is revised.
The assignment process begins when a new chemical is reported in scientific literature or submitted to a regulatory body. The CAS database then validates the molecular formula, structure, and synonyms. Only after verification is the number issued. For cyclohexane, the structure is confirmed as C₆H₁₂, a six-membered ring with all carbon atoms saturated.
For reference, the CAS number of benzene is 71-43-2. Unlike cyclohexane, benzene contains alternating double bonds and is carcinogenic. The difference in CAS numbers reflects their distinct chemical identities and hazard profiles. Similarly, ethyl acetate has the CAS number 141-78-6. These numbers allow regulators and researchers to track each compound independently.
In laboratory settings, the CAS number 110-82-7 is required on inventory logs, procurement forms, and waste disposal manifests. It enables automated tracking through chemical management software such as ChemStation or LabVantage. Without this identifier, cross-referencing safety data becomes unreliable.
Regulatory agencies like the U.S. Environmental Protection Agency (EPA) and the European Chemicals Agency (ECHA) use CAS numbers to classify chemicals under frameworks like REACH and TSCA. Cyclohexane is listed under EPA's Toxic Substances Control Act (TSCA) with the CAS number 110-82-7. This allows enforcement actions based on exposure limits and reporting thresholds.
A real-world example occurred in 2019 when a university lab reported a spill of cyclohexane. Emergency responders used the CAS number 110-82-7 to access the correct safety data sheet. The document specified that cyclohexane is flammable (flash point −2 °C), requires ventilation, and must be stored away from oxidizers. Without the CAS number, the response could have been delayed or misdirected.
Some users mistake the CAS number for a molecular weight or IUPAC name. The CAS number 110-82-7 is not derived from structure-it is assigned after validation. Molecular weight for cyclohexane is 84.16 g/mol, and its IUPAC name is cyclohexane. These are separate identifiers.
Another frequent error is confusing cyclohexane with cyclohexanol (CAS 98-82-8) or cyclohexene (CAS 110-83-8). These compounds share the same parent ring but differ in functional groups. Cyclohexane is purely hydrocarbon; cyclohexanol has an OH group; cyclohexene has a double bond. Their CAS numbers differ by just one digit, highlighting the need for accuracy.
Even minor typos cause major issues. Entering 110-82-8 instead of 110-82-7 points to cyclohexene, which has different toxicity and reactivity profiles. In industrial processes, such errors can result in incorrect safety protocols or failed compliance audits.
Consider a pharmaceutical manufacturer sourcing cyclohexane as a solvent. The supplier must provide a certificate of analysis listing the CAS number 110-82-7. Regulatory auditors verify this during inspections. If the number is missing or incorrect, the batch may be rejected.
When searching scientific databases like PubChem or Reaxys, entering "cyclohexane" returns multiple entries. But adding "110-82-7" narrows results to the correct compound. In PubChem, the entry for CAS 110-82-7 includes 3D structure files, boiling point (80.7 °C), and toxicity data.
Table below compares common cyclohexane-related compounds:
| Compound | CAS Number | Molecular Formula | Key Difference |
|---|---|---|---|
| Cyclohexane | 110-82-7 | C₆H₁₂ | Saturated ring, no functional groups |
| Cyclohexene | 110-83-8 | C₆H₁₀ | One double bond, more reactive |
| Cyclohexanol | 98-82-8 | C₆H₁₁OH | Hydroxyl group, less volatile |
These differences affect storage, handling, and reaction pathways. The CAS number is the only consistent reference across all contexts.
I once reviewed a lab report where a student listed "cyclohexane" but used the CAS number 110-83-8. The error was caught during peer review because the boiling point cited (70 °C) did not match cyclohexane's actual value (80.7 °C). Correcting the CAS number led to accurate data interpretation and proper safety classification.
This incident underscores that CAS numbers are not optional metadata-they are essential for scientific integrity. They prevent miscommunication across languages, institutions, and regulatory jurisdictions.
The cyclohexane CAS number 110-82-7 is more than a sequence of digits. It is a global standard that ensures consistency, safety, and traceability in chemistry.