2-Chlorotoluene (95-49-8) Physical and Chemical Properties
2-Chlorotoluene
A colorless aromatic chloride used as a solvent and intermediate in specialty chemical synthesis; typically procured for formulation, R&D and industrial manufacturing batches.
| CAS Number | 95-49-8 |
| Family | Aromatic chlorides |
| Typical Form | Colorless liquid |
| Common Grades | EP, JP, USP |
2-Chlorotoluene is an aryl halide: the ortho (o-) isomer of chlorotoluene (1-chloro-2-methylbenzene). Structurally it is a monosubstituted benzene bearing a methyl group at C‑1 and a chlorine atom at the adjacent C‑2 position. The combination of an electron‑donating methyl substituent (hyperconjugation, weak +I) and an electron‑withdrawing chloro substituent (inductive \(-I\), weak resonance donation) produces an aromatic system whose reactivity is governed by competing steric and electronic effects at the ortho position. The benzylic methyl group supplies an activated benzylic hydrogen that is prone to oxidation under appropriate conditions; the aryl–Cl bond is relatively inert to hydrolysis but can participate in substitution under forcing or metal‑mediated conditions.
Electronically and physically, 2-chlorotoluene is non‑polar to moderately lipophilic: it lacks hydrogen‑bond donors or acceptors (H‑bond donor count = 0, H‑bond acceptor count = 0, TPSA = 0) and has a measured XLogP value of 3.4 indicating appreciable partitioning into organic phases. It is volatile at ambient temperatures (measured vapor pressure and Henry’s Law constant indicate a significant vapor‑phase fraction) and is classified among volatile organic compounds (VOCs). The compound is not ionizable across normal environmental pH ranges; it is resistant to hydrolysis but susceptible to benzylic oxidation, electrophilic aromatic substitution, and standard transformations used for aryl halides in industrial organic synthesis.
Common industrial relevance arises from its role as a solvent and as a chemical intermediate: it is used as a feedstock for benzylic chlorination and oxidation to give 2‑chlorobenzyl chloride, 2‑chlorobenzaldehyde, 2‑chlorobenzoic acid and related derivatives that are precursors for dyes, agrochemicals, pharmaceutical intermediates and specialty chemicals. Common commercial grades reported for this substance include: EP, JP, USP.
Basic Physical Properties
Density
Multiple experimental determinations indicate a liquid density above that of water. Representative values: - 1.0825 at \(68\,^\circ\mathrm{F}\) (USCG, 1999) — denser than water; will sink. - 1.0826 @ \(20\,^\circ\mathrm{C}/4\,^\circ\mathrm{C}\). - Relative density (water = 1): 1.08.
These values are consistent with a halogenated aromatic solvent in which the chlorine substituent increases mass density relative to non‑halogenated analogues.
Melting Point
Available experimental values: - \(-35.59\,^\circ\mathrm{C}\). - \(-31.2\,^\circ\mathrm{F}\).
The low melting point indicates that 2‑chlorotoluene is a liquid at typical ambient and refrigeration temperatures encountered in industrial settings.
Boiling Point
Reported experimental values include: - \(158.97\,^\circ\mathrm{C}\). - \(159.2\,^\circ\mathrm{C}\). - \(318.15\,^\circ\mathrm{F}\) (760 mmHg).
The boiling range reflects normal volatility for a substituted toluene; fractional distillation is used industrially to separate ortho from para isomers.
Vapor Pressure
Representative vapor pressure data: - \(3.43\,\mathrm{mmHg}\) at \(25\,^\circ\mathrm{C}\) (determined from experimentally‑derived coefficients). - 10 mmHg at \(109.8\,^\circ\mathrm{F}\). - 4 mmHg at \(77\,^\circ\mathrm{F}\).
Measured vapor pressures indicate a substantial vapor concentration at room temperature; vapors are heavier than air (relative vapor density ≈ 4.4), so vapors can accumulate in low areas.
Flash Point
Reported flash point data: - \(43\,^\circ\mathrm{C}\) (closed cup). - \(126\,^\circ\mathrm{F}\).
The flash point places 2‑chlorotoluene in a flammable liquid category under typical classification schemes; appropriate controls for ignition sources are required.
Chemical Properties
Solubility and Phase Behavior
Experimental solubility and miscibility observations: - Solubility in water = \(374\,\mathrm{mg}\,\mathrm{L}^{-1}\) at \(25\,^\circ\mathrm{C}\). - Solubility in water, g/100 mL at \(20\,^\circ\mathrm{C}\): 0.47. - \(0.009\%\) at \(77\,^\circ\mathrm{F}\) (NIOSH). - Freely soluble in chloroform; miscible with alcohol, acetone, ether, benzene, carbon tetrachloride, and n‑heptane; slightly soluble in water.
These data show limited aqueous solubility and good miscibility in non‑polar and moderately polar organic solvents. Given the log Kow ≈ 3.4, the compound preferentially partitions to organic phases and can bioaccumulate to a moderate extent in aquatic organisms.
Reactivity and Stability
Chemical stability and incompatibilities: - Generally stable to hydrolysis under environmental conditions; not ionizable in water. - Reactive transformations center on benzylic oxidation (to aldehydes, acids), electrophilic aromatic substitution and metal‑mediated cross‑couplings typical for aryl chlorides under forcing conditions. - Incompatibilities: strong oxidizing and reducing agents, amines, nitride/azo/diazo compounds, alkali metals, epoxides. Reported violent reaction with dimethyl sulfoxide (DMSO). - Combustion produces irritating and potentially toxic chloride‑containing combustion products; containers may rupture on heating.
Handling and process design should account for flammability, vapor accumulation, and incompatibilities with oxidizers and reactive nitrogen/metal reagents.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
Selected energetic and thermal properties (experimental values): - Heat of combustion: \(-3747\,\mathrm{kJ}\,\mathrm{mol}^{-1}\) at \(18.8\,^\circ\mathrm{C}\). - Heat of vaporization: \(329.1\,\mathrm{J}\,\mathrm{g}^{-1}\) at \(100\,^\circ\mathrm{C}\). - Heat of fusion: \(79.99\,\mathrm{J}\,\mathrm{g}^{-1}\). - Heat capacity: \(0.355\,\mathrm{J}\,\mathrm{g}^{-1}\,\mathrm{K}^{-1}\).
These values are useful for process energy balances, flammability assessments and thermal hazard evaluations for storage and distillation operations.
Molecular Parameters
Molecular Weight and Formula
- Molecular formula: C7H7Cl.
- Molecular weight: 126.58.
- Exact/monoisotopic mass: 126.0236279.
- SMILES: CC1=CC=CC=C1Cl
- InChI: InChI=1S/C7H7Cl/c1-6-4-2-3-5-7(6)8/h2-5H,1H3
- InChIKey: IBSQPLPBRSHTTG-UHFFFAOYSA-N
(SMILES and InChI strings are provided verbatim for identification and cheminformatics use.)
LogP and Polarity
- XLogP (computed): 3.4.
- Log Kow (reported): 3.42.
- Topological polar surface area (TPSA): 0.
- Hydrogen bond donors: 0; hydrogen bond acceptors: 0.
These descriptors quantify the compound’s hydrophobic character and predict limited aqueous solubility, moderate bioaccumulation potential, and preferential partitioning into organic matrices used in formulations.
Structural Features
- Aromatic ring with ortho methyl and chloro substituents; ortho steric hindrance influences reactivity in electrophilic substitution and may direct further substitution patterns.
- The benzylic methyl group provides an activated site for oxidation or functionalization to benzyl chloride/aldehyde/acid derivatives.
- Rotatable bond count: 0 (rigid aromatic core); molecular complexity value: 70.8 (computed descriptor indicating structural complexity for synthetic and analytical considerations).
Identifiers and Synonyms
Registry Numbers and Codes
- CAS Number: 95-49-8
- EC Number: 202-424-3
- UN Number: 2238
- UN Shipping Name (class context): Chlorotoluenes (UN 2238)
- UNII: 2G7D0YDV9H
- InChIKey: IBSQPLPBRSHTTG-UHFFFAOYSA-N
- SMILES: CC1=CC=CC=C1Cl
Synonyms and Structural Names
Common synonyms reported include: - 2‑Chlorotoluene - o‑Chlorotoluene - ortho‑chlorotoluene - 1‑chloro‑2‑methylbenzene - o‑Tolyl chloride - 2‑methylchlorobenzene - 2‑chlorotoluene, analytical standard
(These synonyms are useful for specification sheets, procurement and inventory systems.)
Industrial and Commercial Applications
Representative Uses and Industry Sectors
- Solvent for organic reactions and industrial applications (compatible with many organic solvents; limited water solubility).
- Chemical intermediate in the manufacture of 2‑chlorobenzyl chloride, 2‑chlorobenzaldehyde, 2‑chlorobenzotrichloride, 2‑chlorobenzoyl chloride and 2‑chlorobenzoic acid — precursors used in dyes, pharmaceuticals, optical brighteners, fungicides and other specialty chemicals.
- Feedstock for production of dichlorotoluenes, 3‑chlorotoluene and o‑chlorobenzonitrile.
- Identified uses in pesticide and disinfectant applications (historical/industrial contexts).
- Relevant industry sectors: organic chemical manufacturing, dye and pharmaceutical intermediate production, coatings/paints (as solvent).
Role in Synthesis or Formulations
2‑Chlorotoluene is employed as a starting material for benzylic functionalizations (chlorination, oxidation) and as an intermediate for preparing a variety of chlorinated aromatic derivatives. It is also used where a moderately non‑polar, halogenated aromatic solvent is required. Typical manufacturing involves chlorination of toluene with catalytic halogenation (e.g., FeCl3) followed by fractional distillation to isolate ortho and para isomers.
Safety and Handling Overview
Acute and Occupational Toxicity
- Acute toxicity indicators:
- LCLo (rat): 4,400 ppm (inhalation exposure example).
- Oral LD50 (rat): \(>1600\,\mathrm{mg}\,\mathrm{kg}^{-1}\).
- Reproductive and systemic toxicity parameters reported include an oral chronic reference dose (RfD) of \(0.02\,\mathrm{mg}\,\mathrm{kg}^{-1}\,\mathrm{day}^{-1}\) and inhalation subchronic reference concentration (RfC) values noted in regulatory summaries.
- Occupational exposure limits:
- Recommended exposure limit (NIOSH/REL): TWA \(50\) ppm (\(250\,\mathrm{mg}\,\mathrm{m}^{-3}\)); STEL \(75\) ppm (\(375\,\mathrm{mg}\,\mathrm{m}^{-3}\)).
- Threshold Limit Value (TLV): \(50\) ppm (8‑hr TWA).
- Health effects: respiratory tract irritation, eye and skin irritation, defatting of skin, central nervous system depression at high concentrations (drowsiness, dizziness), potential organ effects on repeated exposure (liver, kidney, CNS). Vapors are harmful and may cause systemic effects on prolonged or high exposures.
Emergency and first‑aid highlights: - Inhalation: remove to fresh air; seek medical attention if symptoms occur. - Skin contact: flush with water for at least 15 minutes; remove contaminated clothing. - Eye contact: irrigate thoroughly for 20–30 minutes; obtain medical attention. - Ingestion: do not induce vomiting; give water if conscious and seek medical attention.
Storage and Handling Considerations
- Flammability: combustible vapors; flash point \(43\,^\circ\mathrm{C}\) (closed cup) — avoid ignition sources. Above \(43\,^\circ\mathrm{C}\) closed systems, explosion‑proof equipment and ventilation are recommended.
- Storage: store in a cool, well‑ventilated area away from heat and incompatible materials (strong oxidizers, strong reducers, reactive nitrogen compounds, alkali metals, epoxides). Keep containers tightly closed and grounded.
- Spill response: isolate area, prevent entry to sewers/waterways, absorb with inert material for disposal, use explosion‑proof ventilation and avoid sources of ignition.
- Personal protective equipment (PPE): safety glasses or goggles, chemical‑resistant gloves, protective clothing; use local exhaust ventilation or respirators when airborne concentrations may exceed occupational limits. Eyewash and emergency showers should be available in areas of routine use.
- Firefighting: extinguish with alcohol‑resistant foam, CO2, dry chemical or water fog; use water in flooding quantities to cool containers. Combustion may produce toxic chlorine‑containing fumes; firefighters should use positive‑pressure self‑contained breathing apparatus (SCBA).
- Environmental precautions: prevent release to water and soil; the compound is harmful to aquatic organisms and may bioconcentrate. For regulatory classification, transport and disposal follow applicable local and national regulations.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
