What does "a" mean at the end of a refrigerant's designation (R-134a)?

Question

I was studying the designation of names to refrigerants.

The following is the basic formula:

R - (m - 1) ( n + 1) ( o )

where:
m = number of carbon atoms in the refrigerant
n = number of hydrogen atoms in the refrigerant
o = number of fluorine atoms in the refrigerant

So R-134a has:

1 + 1 = 2 carbon atoms
3 - 1 = 2 hydrogen atoms
4 fluorine atoms

What does the 'a' at the end mean?

score 12 · Accepted Answer · edited Jun 17 '20 at 09:44

12

R134a..Here "a" is used to denote that it is an isomer. R134 and R134a have same chemical formula and atomic weight but different chemical structures.

R134 has NBP of about -19 C whereas R134a has a NBP of about -26C.

And dont use capital 'A' in R134a …. "A" denotes that the refrigerant is non -azeotropic.

ResearchGate

edited Jun 17 '20 at 09:44

Community

1

answered Feb 06 '16 at 13:02

morristtu

528
4
12

*same chemical formula and atomic weight but different chemical structures* so does this affect the properties of the refrigerant ? I mean are thermal properties of R134 and R134a different? – Fennekin Feb 08 '16 at 18:16
@Fennekin Correct. "R134" is not useful as a refrigerant due to its molecular properties. A similar trend appears in pharmaceuticals with different isomers of a drug. – morristtu Feb 08 '16 at 18:21

score 2 · Answer 2 · answered Feb 08 '16 at 15:39

2

If a refrigerant contains 'a' at its end it is the isomer of that refrigerant. Example 'R123' is 'C2H2F3Cl2' and 'R123a' is the isomer of the same molecule.

answered Feb 08 '16 at 15:39

Rohit Joshi

83
2
9

What does "a" mean at the end of a refrigerant's designation (R-134a)?

2 Answers2