HFC-1234yf HFC-365mfc

[AastroGuru]

I understood the numbering part of HFC-1234yf or HFC-365mfc.

But what is the procedure to write the alphabets 'yf,' 'mfc' etc.,

example
----F---F---H
----|---|---|
F - C - C = C
----|-------|
----F-------H

This gives HFC-1234
1> one unsaturateed carbon - carbon bond
2> three carbon atoms -1
3> two hydrogen atoms +1
4> four fluorine atoms
this makes 1234.

How to determine 'yf'

For simple substances like HFC-225ca i understand how ca is determined.
c - denotes decreasing order atoms attached to central carbon atom
a - based on side carbon atoms


I didnt have ASHRAE Standard 34. I cant afford $37. Please help.

[NoNickName]

1234yf is not an HFC, but an HFO (hydrofluorolefin).
Olefins are unsaturated compounds AKA alkenes, and have at least one double bond.
There exist an isomer of 1234yf known as 1234ze. In this case, the extra letters just serve for distinguish the isomers. The ze is the 1,3,3,3-tetrafluoropropene and the yf is the 2,3,3,3-tetrafluoropropene

[NoNickName]

I forgot to add that HFC-365 is pentafluorobutane, which has got a number of isomers too. Again the letters only refer to each of them,most famous of which is the 1,1,1,3,3-pentafluorobutane or HFC-365mfc

[AastroGuru]

Thanks for your reply. HFC was a mistake. HFO is right ofcourse. Reg 'yf' i know its one of the isomer. But i didnt get why 'yf' why not 'px' why not 'ac'

My doubt is exactly how the letters form.

does y signify something and f signify something.

I heard something like we have to arrange molecular weight in decreasing order and then we have to pick the letters 'yf' from that list based on our isomer.
2,3,3,3-tetrafluoroprop-1-ene.

Anyhow hats off for your reply.

Thanks

[NoNickName]

Not sure, but what I came up googling is:
y precedes z, and f follows e in the alphabet.
By permutating two atoms in the molecule it's like permutating two letters in the alphabet.

Z and E also means "zusammen" and "entgegen" which are german words meaning "together" and "in opposition to".

From wiki: for alkenes and similar double bonded molecules, the same prioritizing process is followed for the substituents. In this case, it is the placing of the two highest priority substituents with respect to the double bond which matters. If both high priority substituents are on the same side of the double bond, ie. in the cis configuration, then the stereoisomer is assigned a Z or Zusammen configuration. If, by contrast they are in a trans configuration, then the stereoisomer is assigned an E or Entgegen configuration. In this case the identifying letters are derived from German for 'together' and 'in opposition to', respectively.