Sina Ebnesajjad - Concise Handbook of Fluorocarbon Gases

Table 2.2Examples of main commercial classes of fluorocarbons [7].

In the case of isomers of propene series, each has the same number, with the isomers distinguished by two appended lowercase letters. The first appended letter indicates the substitution on the central carbon atom:

Table 2.3List of hydrochlorofluorocarbon (HCFC) refrigerants [8].

The second letter designates the substitution on the terminal methylene carbon as defined for the methylene carbon of the propane:

The following schematic summarizes the nomenclature for hydrofluoroolefins:

In the cases where stereoisomers exist, the opposed isomer will be identified by the suffix (E) and the same side isomer will be identified by the suffix (Z). The letters “E” or “Z” are appended at the end of the refrigerant number to show the precedence of the atoms or groups, which are attached to the carbon atoms at either end of the double bond. An example of this system is given in Table 2.6. “E” for Entgegen is similar to trans , where priority atoms or groups are across the double bond from each other. “Z” for Zusammen is similar to cis, signifying that priority atoms or groups are on the same side of a double bond (Figure 2.1).

Table 2.4List of Hydrofluorocarbon (HFC) refrigerants [8].

Priority order of atoms connected to either of the unsaturated carbons is determined by standard CIP (Cahn-Ingold-Prelog) rules of organic nomenclature [11]. In essence, attached atoms of higher atomic number have higher priority: I>Br>Cl>F>O>C>H. In case of a priority tie, the next attached atoms or substituents on the next attached carbon atom are considered, until a priority is determined. In the case of refrigerants, it is more exact and less cumbersome to use atomic mass rather than atomic numbers of the atoms. This is because the sum of the atomic numbers of substituents of CHF 2and CHCl are the same, while the summed atomic masses do differ.

In case of Composition-Designating Prefixes the identifying Number is prefixed by the letter C, for carbon, and preceded by B, C, or F—or their combinations—to signify the presence of bromine, chlorine, or fluorine, respectively. In compounds that also contain hydrogen the codes are preceded by the letter H, to signify the increased deterioration potential before reaching the stratosphere. The compositional designating prefixes for ether substitute an “E” for “C,” such that “HFE,” “HCFE,” and “CFE” refer to hydrofluoroethers, hydrochlorofluoroethers, and chlorofluoroethers, respectively. The composition designating prefixes for halogenated olefins is “CFC”, “HCFC”, or “HFC” referring to chlorofluorocarbon, hydrochlorofluorocarbon, or hydrofluorocarbon, respectively. With substitution of an “O” for the carbon “C” as “CFO”, “HCFO” and “HFO” refer to chlorofluoro-olefin, hydrochlorofluoro-olefin, or hydrofluoro-olefin, respectively.

Table 2.5Main applications for HFC and PFC substitutes 1for Ozone Depleting Fluorocarbons (ODS) [9].

1Several applications use HFCs and PFCs as components of blends. The other components of these blends are sometimes ODSs and/or non-greenhouse gases. Several HFCs, PFCs and blends are sold under various trade names.