1,1,1,2-Tetrafluoroethane

Ball-and-stick Stick Space-filling

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8 atoms, 7 single bonds.

IUPAC name: 1,1,1,2-tetrafluoroethane
Molar mass: 102.0300(84) g/mol
Atoms: 8
SMILES: C(C(F)(F)F)F
InChIKey: LVGUZGTVOIAKKC-UHFFFAOYSA-N
PubChem CID: 13129

Made of

Structural formula of 1,1,1,2-tetrafluoroethane. Each unlabelled corner is a carbon atom, and the two hydrogens on carbon are not drawn. It shows which atoms are joined to which, not the shape. The model above shows the shape.

One small fluorocarbon goes by three names: Refrigerant Gas R 134a when shipped, HFA134a in inhaler studies and HFC-134a in US regulation. Under them it has run car air conditioners, chillers and metered-dose inhalers. Its IUPAC name, 1,1,1,2-tetrafluoroethane, maps the molecule: an ethane chain whose first carbon carries three fluorine atoms and whose second carries a fourth. Two hydrogen atoms are left over, giving the formula C₂H₂F₄ and a molar mass of 102.03 g/mol.

At room temperature it is a colourless gas with a faint, ether-like smell, in CAMEO Chemicals’ description. It is shipped as a liquid held under its own vapour pressure. The Hazardous Substances Data Bank (HSDB) puts its boiling point at −26.5 °C and records it as insoluble in water. It is not combustible, according to the International Chemical Safety Cards (ICSC). Chemically it is unreactive in many situations, though the most active metals can react with it violently, CAMEO Chemicals warns.

Structure and bonding

The model is a two-carbon chain with lopsided ends: a CF₃ group at one, CH₂F at the other. Its readout counts 8 atoms and 7 single bonds, one C–C, four C–F and two C–H. With Labels on, three F symbols crowd one carbon, while the other holds one F and two H, the 1,1,1,2 of the name in atoms. Seen along the C–C bond, the model sets each bond on one carbon between two on the other, its lone fluorine opposite one CF₃ fluorine.

Carbon is tetrahedrally coordinated in most organic compounds, Chem1 notes, and both carbons follow suit; in Ball-and-stick the model’s angles run from 107.8° to 111.3°. Its seven drawn bonds are all single, matching the real molecule. Stick strips it to a short rod branching three ways at each end, its C–F sticks longer than its C–H ones. In Space-filling, fluorine spheres fill most of the outline, the hydrogens mere bumps.

Fluorine’s electronegativity, its pull on electrons shared in a bond, is 3.98 on the Pauling scale to carbon’s 2.55. On Chem1’s account, such a gap shifts the shared electrons toward fluorine, so each C–F bond is polar, though the viewer marks no charges.

Where it turns up

Since 1994 it has been the most common refrigerant in car air conditioning, according to the US Environmental Protection Agency (EPA). It is also the main one used to retrofit systems built for CFC-12, a chlorofluorocarbon (CFC). Air-conditioning chillers use it too, according to HSDB, and Haz-Map, an occupational health database, lists it as a blowing agent for foams. Hydrofluorocarbons (HFCs) such as this one have no known natural sources, the EPA says.

Under the name HFA134a it is a propellant in metered-dose inhalers, and salbutamol and salmeterol inhalers have been reformulated with it (HSDB). Industry makes it from trichloroethylene and hydrogen fluoride, HSDB records. US production lay between 100 million and 250 million pounds in each year from 2020 to 2023, in EPA chemical data.

Why it matters

It spread as a stand-in for ozone-depleting refrigerants. HFCs contain no chlorine, so their ozone depletion potential, a number for the ozone loss a substance causes, is zero (EPA). How chlorine attacks the ozone layer is told on the ozone page. Car makers began switching with 1992 model-year vehicles, and by the 1995 model year every new air-conditioned car sold in the United States used it.

The cost is warming: its global warming potential is 1,430 times carbon dioxide’s (EPA), a measure explained on the nitrous oxide page. It is also the most abundant HFC in the atmosphere, on the EPA’s account. NOAA (the US National Oceanic and Atmospheric Administration) counts it among 17 halogenated gases supplying the last 4 per cent of warming from long-lived greenhouse gases in 2024. On NOAA’s figures, CFCs and related gases still exert more warming than all hydrochlorofluorocarbons (HCFCs) and HFCs combined.

The 2016 Kigali Amendment to the Montreal Protocol set a worldwide HFC phase-down. Cuts to 18 HFCs began in 2019 (NOAA), and the United States ratified the amendment on 31 October 2022.

Properties

Properties of 1,1,1,2-tetrafluoroethane Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 13129.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂H₂F₄
Molar mass	102.0300(84) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	2
Hydrogen atoms	2
Fluorine atoms	4
Bonds	7
PubChem molecular weight	102.03 g/mol	g/mol	PubChem

Safety

1,1,1,2-Tetrafluoroethane is classed under the Globally Harmonized System (GHS) as a gas under pressure, with the signal word Warning. Fast-evaporating liquid can cause frostbite, and the compound may affect the central nervous and cardiovascular systems (ICSC). The vapour is heavier than air and can replace the available oxygen, and in closed or confined spaces it may cause dizziness or asphyxiation without warning. The PubChem Laboratory Chemical Safety Summary gathers these hazards and notes the workplace exposure limits that apply.

Questions

What does a 1,1,1,2-tetrafluoroethane molecule look like?

In the 3D model it is a two-carbon chain of 8 atoms joined by 7 single bonds. One carbon carries three fluorine atoms; the other carries one fluorine and both hydrogens, which is what the numbers 1,1,1,2 in the name record. Each carbon sits at the centre of a tetrahedral set of four neighbours. With two such centres and no single central atom, the molecule as a whole takes no one shape name.

Why is tetrafluoroethane used in inhalers?

A metered-dose inhaler needs a propellant, which Medical Subject Headings (MeSH) defines as a compressed gas or vapour that expands through a valve when the pressure drops and carries another substance out. Tetrafluoroethane, named HFA134a in inhaler studies, was taken up to replace chlorofluorocarbon propellants without harming ozone. In the body most of it is breathed out within minutes, and little is metabolised, according to the Hazardous Substances Data Bank.

Is R-134a being phased out?

Yes, in many uses. The US Environmental Protection Agency (EPA) has ruled it unacceptable in new household refrigerators since 1 January 2021, and as an aerosol propellant since 20 July 2016 except for listed uses such as medical inhalers. Car air conditioning, about 24 per cent of global hydrofluorocarbon (HFC) consumption on the EPA's estimate, began moving to HFO-1234yf in 2012. An EPA rule of October 2023 restricts R-134a in new light-duty vehicles from model year 2025.

Is 1,1,1,2-tetrafluoroethane flammable?

No. The International Chemical Safety Cards class it as not combustible, and the EPA lists it as non-flammable among propellant substitutes. Heat still matters: when heated to decomposition it gives off toxic fluoride vapours, and in a fire it releases irritating or toxic gases. Its other hazards, from frostbite to oxygen pushed aside in closed spaces, are gathered in its PubChem Laboratory Chemical Safety Summary.