The key difference between CFC and HCFC is that the CFC contains only carbon, fluorine and chlorine atoms whereas HCFC contains hydrogen, carbon, fluorine and chlorine atoms. More importantly, CFC causes serious ozone depletion but HCFC, comparatively, has a much lesser impact on the ozone layer.
The chemical structures of both CFC and HCFC relate to each other according to the chemical elements present in these structures. However, concerning the chemical structure, the difference between CFC and HCFC is that the CFC has no hydrogen atom while the HCFC contains hydrogen atom. CFC is well-known as a contributor to ozone depletion. Hence, it is a harmful substance. HCFC is a good substitute for this harmful substance.
CONTENTS
1. Overview and Key Difference
2. What is CFC
3. What is HCFC
4. Side by Side Comparison – CFC vs HCFC in Tabular Form
5. Summary
What is CFC?
CFC is a class of compounds that contain fully halogenated paraffin hydrocarbons. These compounds contain carbon, fluorine and chlorine atoms only. The carbon atoms in these compounds form covalent bonds in a tetrahedral symmetry. Manufacturers produce these compounds as volatile derivatives of methane, ethane and propane. The general brand name for this class is “Freon”. The most common compound of this class is dichlorodifluoromethane. The common uses of these compounds are as refrigerants, propellants and as solvents. However, later research found that these compounds contribute to ozone depletion. Therefore, these compounds were replaced with some harmless compounds such as HCFCs.
Furthermore, the physical properties of these compounds changes with the number and type of halogen present in the compound. Generally, they are volatile. But the volatility is less than their parent molecules (alkanes). The less volatility arises due to the molecular polarity which is induced by the halides; these halides result in intermolecular interactions which leads to increase the boiling point, thus decrease the volatility. However, because of their polarity, these compounds are good solvents. Moreover, their boiling point makes them good refrigerants. In addition to that, these compounds have higher densities compared to the corresponding alkanes.
Figure 01: Ozone Depletion
Further, the most important reaction of CFC is photo-induced scission of a C-Cl bond. We can write it as follows.
CCl3F → CCl2F. + Cl.
This reaction forms chlorine radical. It behaves very differently from the chlorine molecule; Cl2. And this radical lives a long time in the upper atmosphere. There, it catalyzes the conversion of ozone into oxygen molecules. Thus, it depletes the amount of ozone.
What is HCFC?
HCFC is a class of compounds having a chemical structure very similar to CFC. However, unlike CFC, these compounds contain hydrogen atom, in addition to the carbon, fluorine and chlorine atoms. Under normal conditions, these are either gases or highly evaporative liquids. Generally, they are stable and unreactive.
These compounds are very useful substituents for CFCs. They are useful as refrigerants and in insulative foams. However, people do not use it as a solvent, and it is banned to use as a solvent in many developed countries. More importantly, these compounds do not have any immediate impacts on the environment after releasing to the environment. Due to their volatile nature, they can involve in reactions that produce ozone at the lower atmosphere level that can damage plants. Since they are not as stable as CFC and thus not so persistent in the atmosphere, the effects on the atmosphere are very less. But still, these compounds can end up in upper atmosphere causing a very slow depletion of ozone.
What is the Difference Between CFC and HCFC?
CFC is a class of compounds that contain fully halogenated paraffin hydrocarbons. These compounds contain only carbon, fluorine and chlorine atoms. More importantly, CFC causes serious ozone depletion. HCFC is a class of compounds having a chemical structure very similar to CFC. But, they contain hydrogen atom, in addition to the carbon, fluorine and chlorine atoms. However, HCFC has a very less impact on the ozone layer because it undergoes photochemical decomposition before it reaches the upper atmosphere. This is an important difference between CFC and HCFC.
Summary – CFC vs HCFC
Both CFC and HCFC compounds are useful as refrigerants, but CFCs are not in use due to their serious environmental impacts. The key difference between CFC and HCFC is that the CFC contains only carbon, fluorine and chlorine atoms whereas the HCFC contains hydrogen atom in addition to carbon, fluorine, and chlorine atoms.
Reference:
1. “Chlorofluorocarbon.” Wikipedia, Wikimedia Foundation, 31 July 2018. Available here
2. “Hydrochlorofluorocarbons (HCFCs).” Pollutant Fact Sheet. Available here
Image Courtesy:
1.”NASA and NOAA Announce Ozone Hole is a Double Record Breaker”By NASA (Public Domain) via Commons Wikimedia