Hydrofluorocarbons

Hydrofluorocarbons (HFCs) are a group of fluorinated organic compounds that contain only hydrogen and fluorine. They are used as refrigerants, solvents, and propellants. HFCs have replaced chlorofluorocarbons (CFCs) in many applications because they do not deplete the ozone layer. However, HFCs are potent greenhouse gases, with some having global warming potentials that are thousands of times higher than carbon dioxide.

HISTORY

The first hydrofluorocarbon was synthesized by Henri Moissan in 1886. In the 1930s, Frédéric Soret discovered that hydrofluorocarbons could be used as refrigerants. In the 1940s, scientists began using hydrofluorocarbons as solvents and propellants. In the 1950s, CFCs were developed for use as refrigerants. CFC production increased rapidly in the following decades due to their effectiveness and low cost. However, it was soon discovered that CFCs were damaging the Earth’s ozone layer. As a result, production of CFCs was phased out under the Montreal Protocol in 1987. HFCs were introduced as replacements for CFCs because they do not damage the ozone layer. Since then, HFC production has grown rapidly due to their continued use in refrigeration and other applications such as foams and aerosol propellant sprays..

PHYSICAL AND CHEMICAL PROPERTIES OF HYDROFLUOROCARBONS
H FC molecules consist of one or more carbon atoms bonded to hydrogen atoms and fluoro atoms (-F). The number after “HF” corresponds to the average number of carbons in each molecule: HF-134 is made up of 1 carbon atom while HF-23 is made up 2 carbons atoms on average . Hydrofluorocarbons are non – polar molecules; this means that they do not interact strongly with other molecules . This gives them several important properties:
•They do not dissolve in water
•They have low toxicity • They evaporate easily All these properties make H FCS useful for various industrial applications like fire extinguishers , air conditioning , cleaning products etcetera . However , these same properties make H FCS very harmful to both human health and environment : when released into atmosphere , they can last for years without breaking down ; during this time they contribute significantly to climate change by trapping heat from sun inside Earth’ s atmosphere .

USES OF HYDROFLUOROCARBONS HF CS have replaced chlorofluorocarbons (C FCS) in many applications because they donot deplete Earth’ s ozone laye r . Ozone depletion occurs when chlorine or bromine molecules break apart ozone molecules (03)in stratosphere ; ultraviolet light from sun then splits these chlorine or bromine radicals which start chain reaction leading to breakdown of more 03molecules . This reduces amount of 03 present in stratosphere which filters out harmful UVB radiation before it reaches Earth’ s surface ; less 03 results in more UVB exposure for life forms on ground including humans which can cause skin cancer , cataracts etcetera . While HCFS donot directly harm 03molecules , once released into atmosphere they eventually turn into substances like trifluoroacetic acid (TFA )which does participate in chemical reactions that destroy 03molecules Most common uses of HCFS include : Refrigeration : Because HCFS evaporate easily at relatively low temperatures ,they can be used as “ working fluids “ inside refrigerator compressors where they absorb heat from inside fridge then release it outside when compressed gas cools down again upon expansion . Air Conditioning : Same principle applies here where HCFS fluids help remove heat from indoors then release it outdoors Solvents : HCFS liquids like n – propane dif luoroethane(HCFO -1224ya )and pentaf luoroethane(HCFO -1225cb )are used industrywide because their low boiling points enable easy evaporation Fire Extinguishers: Aqueous film forming foam(AFFF) mixtures containing about 70% per f luoroalkyl carboxylic acids(PFAAs)like perf luorosulfonic acid sodium salt decahydrate(PFOSNa2·10H2O )and N-ethylperf luorosulfonamide((EtF3S0N)-N-Me)(NEtFSA),15% alcohol ethoxylate surfactant solution like polyethylene glycol tert-butyl ether 25EO/75PO blend ((C4H9OH)-CH2-(CH2-)3-(OCH2CH2-)25-(OC4H9)) n=3~7),and 15% perfluoropropane ((CF3)-CF-)n show good fire suppression performance against Class B flammable liquid fires like heptane oil pool fires without harming people or equipment near fire site Propellant Sprays: Dif luoroethane(HCFO -1211cb ),trif luo ropropane(HCFO-1301),and tetrafluo ropropene(HCFO-1405ca )are often found pressurized inside spray cans where their high vapor pressure enables easy dispensing onto desired surfaces