Difluoromethane (75-10-5) Physical and Chemical Properties
Difluoromethane
Hydrofluorocarbon refrigerant (HFC‑32) supplied as a compressed, liquefiable gas for industrial and commercial cooling applications.
| CAS Number | 75-10-5 |
| Family | Fluoromethanes (HFC refrigerants) |
| Typical Form | Colorless gas (stored as liquefied compressed gas) |
| Common Grades | BP, EP, USP |
Difluoromethane is a low-molecular-weight hydrofluorocarbon of the fluoromethane structural class; its molecular formula is \(\ce{CH2F2}\). Structurally it is the methane core with two hydrogen atoms replaced by fluorine atoms, producing a small, symmetric substituent set that imparts significant C–F bond character, strong C–F bond polarity and a modest permanent dipole. The absence of polar functional groups capable of hydrogen bonding combined with two highly electronegative fluorine atoms yields low polar surface area and limited aqueous solubility while preserving gas-phase stability and resistance to hydrolysis under normal environmental conditions.
Physicochemical behavior is dominated by volatility and weak intermolecular interactions: difluoromethane is a colorless gas at ambient conditions and readily liquefies under modest pressure. It exhibits low lipophilicity (\(\log K_{\mathrm{ow}}\) and computed XLogP values are small), limited biodegradability, and atmospheric persistence controlled primarily by reaction with hydroxyl radicals. The substance is non-ionic, has no hydrogen-bond donors, and typically shows low propensity to partition into solids or sediments; it is widely used where high volatility and low ozone-depletion potential are required, most notably as a refrigerant and as a tracer gas in analytical applications.
Common commercial grades reported for this substance include: BP, EP, USP.
Basic Physical Properties
Density
Reported experimental densities for liquid difluoromethane include \(0.961\) (value reported at \(25\,^\circ\mathrm{C}\)), \(1.052\) (reported at \(0\,^\circ\mathrm{C}\), liquid) and \(1.2139\ \mathrm{g\,cm^{-3}}\) at \(-52\,^\circ\mathrm{C}\). The critical (maximum) density is reported as \(0.430\) (dimensionless in the reported context). These values reflect the strong temperature dependence typical of low-molecular-weight condensed halogenated gases and are relevant for mass–volume calculations in liquefied-gas handling and refrigeration system charging.
Melting Point
The reported melting point is \( -136.8\,^\circ\mathrm{C} \).
Boiling Point
The reported normal boiling point (at ambient pressure) is \( -51.65\,^\circ\mathrm{C} \).
Vapor Pressure
The vapor pressure at \(25\,^\circ\mathrm{C}\) is reported as \(1.26\times10^{4}\ \mathrm{mm\ Hg}\). This very high vapor pressure indicates that the compound exists predominantly as a gas under standard ambient conditions and explains its ready vaporization from liquid reservoirs.
Flash Point
No experimentally established value for this property is available in the current data context.
Chemical Properties
Solubility and Phase Behavior
Difluoromethane is described as essentially a gas at ambient conditions and is reported to be insoluble or only sparingly soluble in water; experimental solubility is reported as \(0.44\%\) (w/w) in water at \(25\,^\circ\mathrm{C}\). It is reported soluble in ethanol. The very high vapor pressure and low Henry’s law partitioning resistance drive rapid volatilization from aqueous and soil surfaces; volatilization is a dominant environmental fate process. Liquefaction under pressure is routine for storage and transport in pressurized cylinders.
Reactivity and Stability
Difluoromethane is thermally stable under normal handling conditions but is a flammable gas that forms explosive mixtures with air. It is incompatible with strong oxidizing and reducing agents and may react with certain metals (notably reported concerns with aluminum) and reactive organics. Upon thermal decomposition or high-temperature combustion it can release toxic fluorinated species (fluoride-containing decomposition products). It does not contain hydrolyzable functional groups and is not expected to hydrolyze under environmental pH conditions.
Thermodynamic Data
Standard Enthalpies and Heat Capacity
No experimentally established value for this property is available in the current data context.
Molecular Parameters
Molecular Weight and Formula
Molecular weight (reported): \(52.023\). The molecular formula is \(\ce{CH2F2}\).
- Exact/monoisotopic mass (reported): \(52.01245639\).
LogP and Polarity
Reported partitioning metrics: computed XLogP3-AA is \(1\) and reported experimental log Kow is \(0.20\) (presented as log Kow = 0.20). Topological polar surface area (TPSA) is reported as \(0\). The compound has no hydrogen-bond donors and a reported hydrogen-bond acceptor count of \(2\) (two fluorine atoms). These values indicate low overall polarity with limited potential for classical hydrogen-bond interactions; partitioning into lipophilic phases is modest.
Structural Features
Key structural descriptors: heavy atom count \(3\); rotatable bond count \(0\); molecular complexity \(2.8\) (computed). The dipole moment is reported as \(1.98\ \mathrm{D}\), consistent with a moderate molecular polarity arising from C–F bond dipoles that do not cancel completely. The small size and lack of conformational flexibility produce simple gas-phase rotational–vibrational spectra and facilitate rapid diffusion and volatilization.
Additional reported critical constants and volumetric data: critical temperature \(351.28\ \mathrm{K}\), critical pressure \(5.79\ \mathrm{MPa}\), and critical volume \(121\ \mathrm{cm^{3}\,mol^{-1}}\).
Identifiers and Synonyms
Registry Numbers and Codes
- CAS Number: 75-10-5
- EC Number: 200-839-4
- UN Number (transport context): reported as UN 3252 (difluoromethane / refrigerant gas R‑32)
- UNII: 77JW9K722X
- ChEBI ID: CHEBI:47855
- ChEMBL ID: CHEMBL115186
Structural identifiers (inline code):
- SMILES: C(F)F
- InChI: InChI=1S/CH2F2/c2-1-3/h1H2
- InChIKey: RWRIWBAIICGTTQ-UHFFFAOYSA-N
Synonyms and Structural Names
Common synonyms and commercial identifiers reported include: difluoromethane; methylene difluoride; methylene fluoride; \(\ce{CH2F2}\); R‑32; HFC‑32; Freon‑32; Genetron 32; Khladon 32; FC 32. These synonyms are used across technical, regulatory and commercial contexts; the refrigerant designator R‑32 and HFC‑32 are commonly used in refrigeration and HVAC technical specifications.
Industrial and Commercial Applications
Representative Uses and Industry Sectors
Difluoromethane is widely used as a refrigerant (noted as HFC‑32 / R‑32) because it offers high volatilization and zero ozone-depletion potential relative to legacy chlorofluorocarbons. Reported industry sectors include refrigeration and air‑conditioning systems, functional closed‑system fluids, and machinery/appliance manufacturing where refrigerants are required. It is also used as a tracer gas in gas‑phase measurement applications and as a feedstock or intermediate in select chemical syntheses.
Reported production volumes indicate large-scale commercial manufacture and use in refrigerant production and related sectors.
Role in Synthesis or Formulations
In formulations the primary role is as a working fluid (refrigerant) and as a volatile tracer in analytical chemistry. The substance serves in closed‑system refrigeration cycles and as a replacement for higher‑ozone‑depletion refrigerants; it may also be used as a reagent or solvent in select organic transformations where a volatile, inert fluorinated medium is required.
Safety and Handling Overview
Acute and Occupational Toxicity
Acute inhalation exposure primarily poses asphyxiation and central nervous system depressant hazards at high concentrations (dizziness, narcosis); it has been reported that vapors may cause dizziness or loss of consciousness without warning. Animal inhalation studies report low systemic absorption from the alveoli (a small percentage of inhaled dose is absorbed systemically), with rapid exhalation of the absorbed fraction; carbon dioxide is a principal metabolic product for the minor fraction metabolized. Reported acute LC50 (rat) is \(1{,}890{,}000\ \mathrm{mg\,m^{-3}}\) for a 4‑hour exposure, indicating very high inhalation concentrations are required for lethality in that study design; nevertheless, occupational exposure limits and conservative controls are appropriate because of narcotic effects and asphyxiation risk.
Decomposition or burning can produce toxic, corrosive fluorinated species (fluoride‑containing products); inhalation or exposure to these combustion products is hazardous.
For immediate medical response: remove to fresh air, administer oxygen if breathing is difficult, and treat frostbite or cold burns from contact with liquefied material according to standard clinical protocols. Seek emergency medical attention for significant exposures.
Storage and Handling Considerations
- Store in appropriate high‑pressure gas cylinders or refrigeration system circuits designed for liquefied pressurized gases; containers should be stored upright, secured, and protected from excessive heat.
- Eliminate sources of ignition in storage and handling areas; grounding and bonding of equipment is recommended to prevent static discharge.
- Provide adequate ventilation and continuous gas‑detection in confined spaces or mechanical rooms to prevent accumulation of flammable atmospheres; vapors may be heavier than air and can collect in low‑lying areas.
- Use personal protective equipment appropriate for pressurized cryogenic/liquefied gases: thermal protective clothing and positive‑pressure self‑contained breathing apparatus (SCBA) for emergency response to large releases or fires; appropriate eye/face protection and insulated gloves when handling cryogenic liquid contact risk exists.
- Avoid contact of liquefied gas with skin or eyes (frostbite hazard) and avoid incompatible materials such as strong oxidizers and reactive metal systems (reported incompatibility with aluminum in some circumstances).
- For fire incidents: do not extinguish a leaking gas fire unless the leak source can be stopped safely; use dry chemical or CO2 for small fires and flooding water fog at a distance for large fires while cooling exposed containers. Cylinders exposed to fire may vent, rupture or rocket; isolate and evacuate per standard emergency procedures.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
Safety and Regulatory Notes (brief)
- The substance is classified as a flammable gas and is transported under UN 3252 in many jurisdictions; it is handled as a pressurized liquefied gas in commerce.
- Global warming potential (100‑year time horizon) is reported as \(675\) in one experimental context; atmospheric lifetime is controlled by reaction with hydroxyl radicals (reported rate constant on the order of \(1.10\times10^{-14}\ \mathrm{cm^{3}\,molecule^{-1}\,s^{-1}}\)), giving a multiyear atmospheric lifetime and non‑zero contribution to climate forcing.
For detailed hazard, transport and regulatory information, users should refer to the product‑specific Safety Data Sheet (SDS) and local legislation.
