Читать книгу Concise Handbook of Fluorocarbon Gases - Sina Ebnesajjad - Страница 26
2.3 Designations for Fluorocarbons
ОглавлениеFluorocarbon compounds are designated by a combination of letters and numbers (e.g., CFC-11, HCFC-142b). In the latter example, the lower-case b refers to an isomer. It has no relationship to the chemical formula (C2H3F2Cl), rather it designates a particular structural arrangement of the atoms in the molecule. For example, HCFC-142b identifies the isomer in which all three hydrogen atoms are attached to the same carbon atom, and the structural formula is written as CH3CF2Cl. By contrast, HCFC-142 (without the b) refers to an arrangement in which one carbon atom is attached to two hydrogen atoms and one chlorine atom, while the other carbon atom is attached to the third hydrogen atom and two fluorine atoms (CH2ClCHF2).
To find the number, given the chemical formula: consider the number as consisting of 3 digits: a, b, and c. For 2-digit numbers (e.g., CFC-11) one digit is zero (e.g., CFC-011).
a is the number of carbon atoms minus 1;
b is the number of hydrogen atoms plus 1;
c is the number of fluorine atoms.
| For CFCl3: | a = the number of carbon atoms (1) minus 1 = 0 |
| b = the number of hydrogen atoms (0) plus 1 = 1 | |
| c = the number of fluorine atom = 1 |
and the compound is CFC-011, or CFC-11.
Similarly:
CCl2F2 is CFC-012
C2Cl3F3 is CFC-113
To find the chemical formula, given the number: first add 90 to the abc number, to obtain a 3-digit definite number (def), where:
d is the number of carbon atoms;
e is the number of hydrogen atoms;
f is the number of fluorine atoms; and
2d + 2 - e - f = the number of chlorine atoms.
For CFC-11: 90 + 11 = 101, so the number of carbon atoms is 1, the number of hydrogen atoms is zero, the number of fluorine atoms is 1, and the number of chlorine atoms is (2 + 2 - 0 - 1 = 3). So the chemical formula for CFC-11 is CFCl3. That is, it has 1 carbon atom, no hydrogen, 1 fluorine atom, and 3 chlorine atoms.
| Similarly: | CFC-12: 12 + 90 = 102; 4-2 = 2 Cl; the chemical formula is: CCl2F2 CFC-113: 113 + 90 = 203; 6-3 = 3 Cl; the chemical formula is: C2Cl3F3 HCFC-142b: 142 + 90 = 232; 6-5 = 1 Cl; the chemical formula is: C2H3F2Cl |
Halons are fluorocarbons with at least one bromine atom.
Halon (no hydrogen number) nomenclature is relatively simple; each halon has an abcd number, where:
a = the number of carbon atoms;
b = the number of fluorine atoms;
c = the number of chlorine atoms, and
d = the number of bromine atoms.
C2F4Br2 is Halon 2402. And, an example going the other way Halon 1211 is CF2ClBr. It is not possible to speak about fluorocarbons without bringing up the issue of the effect of these compounds on the Earth’s Ozone Layer and the Montreal Protocol (described later in this section) that has banned most or all of those fluorocarbons. Examples of the three main commercial classes, based on their interaction with ozone, of fluorocarbons are summarized in Table 2.2. CFC’s have been completely phased out and the others, except for HFOs, are in various stages of being phased out.
Hydrofluorocarbons and, to a very limited extent, perfluorocarbons (PFCs), serve as alternatives to ozone depleting substances phased out under the Montreal Protocol. Tables 2.3 and 2.4 summarize HCFC, HFCs and PFCs fluorocarbons. Applications of HFCs are presented in Table 2.5.
The usage of olefinic fluorocarbons required an extension of the designation system by ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers). The following descriptions have been adopted from an ASHRAE publication [10].
Olefin: an organic (carbon containing) compound characterized by the presence of one or more double bonds between carbon atoms in the molecule. Such a compound can also be described as being unsaturated.
Unsaturated: as used in this standard, an organic (carbon containing) compound in which one or more carbon atom is joined to other carbon atoms by a carbon-carbon double bond. Such a compound can also be described as an olefin.
The identifying numbers assigned to the hydrocarbons and halocarbons of the methane, ethane, ethene, propane, propene, and cyclobutane series are such that the chemical composition of the compounds can be explicitly determined from the refrigerant numbers, and vice versa, without ambiguity. The molecular structure can be similarly determined for the methane, ethane, ethene, and most of the propane and propene series from only the identification number.
The carbon atoms are numbered sequentially, in order of appearance, with the number 1 assigned to the end carbon with the greatest number of hydrogen substituents (i.e., number of halogenated atoms substituted for hydrogen on the alkane end carbon atoms). In the case where both end carbons of a saturated compound contain the same number of (but different) halogen atoms the number 1 shall be assigned to the first end carbon, defined as having the largest number of bromine, then chlorine, then fluorine, and then iodine atoms. If the compound is an olefin, then the end carbon nearest to the double bond will be assigned the number “1”, as the presence of a double bond in the backbone of the molecule has priority over substituent groups on the molecule.
Table 2.2 Examples of main commercial classes of fluorocarbons [7].
| Fluorocarbon type | Description | Applications |
| CFC | Substance that contains chlorine and has strong characteristics of destroying the ozone layer. Examples: CFC-11, 12, 113 etc. | It has been widely used with refrigerant, blowing, solvent, and aerosol propellant, but in accordance with Montreal Protocol, those have been completely banned production and imports by the end of 1995. |
| HCFC | It contains chlorine but it also contains hydrogen, therefore propensity to destroy the ozone layer is considerably weakened (low ODP).Examples: HCFC-22, 123, 141b, 142b etc. | It has been widely used with refrigerant, blowing, solvent, and aerosol propellant, but in accordance with Montreal Protocol, those are on the way of total abolition. Depending on types and uses, some have been totally abolished. (Example, HCFC-141b for PU blowing agent) |
| HFC | It does not contain chlorine and has hydrogen that does not destroy ozone layer. Examples: HFC-23, 32, 125, 134a, 143a, 152a etc.HFC blend refrigerants R-410A, 407C, 404A. | Refrigerant: Refrigerator, various refrigeration equipment, mobile airconditioning, room air-conditioner, package air-conditioner etc. Blowing agent, solvent, and aerosol propellant. |
| HFO | It does not contain chlorine and has hydrogen. Does not destroy ozone layer. Plus it has no impact on global warming Examples: R-1234yf (CF3CF=CH2), R-1234ze (CF3CH=CHF). | Refrigerator, various refrigeration equipment, mobile air-conditioning, room air-conditioner, package airconditioner etc. Blowing agent, solvent, and aerosol propellant. |
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:
| - Cl | x |
| - F | y |
| - H | z |
Table 2.3 List of hydrochlorofluorocarbon (HCFC) refrigerants [8].
| Product R-Number | ODP | GWP | |
| 22 | 0,055 | Medium | 1810 |
| 123 | 0,060 | Medium | 77 |
| 401A | 0,033 | Medium | 1182 |
| 401B | 0,036 | Medium | 1288 |
| 402A | 0,019 | Medium | 2788 |
| 402B | 0,030 | Medium | 2416 |
| 408A | 0,024 | Medium | 3152 |
| 409A | 0,046 | Medium | 1909 |
The second letter designates the substitution on the terminal methylene carbon as defined for the methylene carbon of the propane:
| =CCl2 | a |
| =CClF | b |
| =CF2 | c |
| =CHCl | d |
| =CHF | e |
| =CH2 | f |
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 2.4 List of Hydrofluorocarbon (HFC) refrigerants [8].
| Product R- Number | ODP | GWP | |
| 23 | 0 | Zero | 14800 |
| 32 | 0 | Zero | 675 |
| 134A | 0 | Zero | 1430 |
| 404A | 0 | Zero | 3922 |
| 407A | 0 | Zero | 2107 |
| 407C | 0 | Zero | 1774 |
| 407F | 0 | Zero | 2088 |
| 417A | 0 | Zero | 2346 |
| 422A | 0 | Zero | 3143 |
| 422D | 0 | Zero | 2729 |
| 423A | 0 | Zero | 2280 |
| 424A | 0 | Zero | 2440 |
| 427A | 0 | Zero | 2138 |
| 428A | 0 | Zero | 3607 |
| 434A | 0 | Zero | 3245 |
| 437A | 0 | Zero | 1805 |
| 438A | 0 | Zero | 2265 |
| 442A | 0 | Zero | 1888 |
| 507A | 0 | Zero | 3985 |
| 508B | 0 | Zero | 13396 |
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 CHF2 and 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 2.5 Main applications for HFC and PFC substitutes1 for Ozone Depleting Fluorocarbons (ODS) [9].
| Chemical | Refrigeration and air conditioning | Fire suppression and explosion protection | Aerosols | Solvent cleaning | Foam blowing | Other Application2 | |
| Propellants | Solvents | ||||||
| HFC-23 | X | X | |||||
| HFC-32 | X | ||||||
| HFC-125 | X | X | |||||
| HFC-134a | X | X | X | X | X | ||
| HFC-143a | X | ||||||
| HFC-152a | X | X | X | ||||
| HFC-227ea | X | X | X | X | X | ||
| HFC-236fa | X | X | |||||
| HFC-245fa | X | X | |||||
| HFC-365mfe | X | X | X | ||||
| HFC-43-10mee | X | X | |||||
| PFC-143 (CF4) | X | ||||||
| PFC-116 (C2F6) | X | ||||||
| PFC-218 (C2F8) | |||||||
| PFC-31-10 (C4F10) | X | ||||||
| PFC-51-144 (C6F14) | X |
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.
2Other applications include sterilization equipment, tobacco expansion applications, plasma etching of electronic chips (PFC-116) and as solvents in the manufacture of adhesive coatings and inks.
3PFC-14 (chemically CF4) is used as a minor component of a proprietary blend. Its main use is for semiconductor etching.
4PFC-51-14 is an inert material, which has little or nil ability to dissolve soils. It can be used as a carrier for other solvents or to dissolve and deposit disk drive lubricants. PFCs are also used to test that sealed components are hermetically sealed.
Table 2.6 Propene series isomers [10].
| Isomer | Chemical formula | Stereoisomer | |
| IUPAC | ACS | ||
| R-1234yc | CH2F-CF=CF2 | ||
| R-1234zc | CHF2-CH=CF2 | ||
| R-1234ye(E) | CHF2-CF=CHF | Entgegen | Trans |
| R-1234ye(Z) | CHF2-CF=CHF | Zusammen | Cis |
| R-1234ze(E) | CF3-CH=CHF | Entgegen | Trans |
| R-1234ze(Z) | CF3-CH=CHF | Zusammen | Cis |
| R-1234yf | CF3-CF=CH2 |
IUPAC = International Union of Pure and Applied Chemists
ACS = American Chemical Society
Figure 2.1 Two examples of isomeric hydrofluorooelefin [10].
Halogenated olefins are a subset of halogenated organic [or carbon-containing] compounds. They have significantly shorter atmospheric lifetimes than their saturated counterparts. Examples include: CFC-11, CFC-12, BCFC-12B1, BFC-13B1, HCFC-22, HC-50, CFC-113, CFC-114, CFC-115, HCFC-123, HCFC-124, HFC-125, HFC-134a, HCFC-141b, HCFC-142b, HFC-143a, HFC-152a, HC-170, and FC-C318, and HFC-1234yf or HFO-1234yf.
