The Organic Chemistry of Surfactants - Surfactant Science and Technology - page 45

2.2.3.8. Fluorocarbons
An important modern addition to the spectrum of available hydrophobic function-
alities for the design of surfactants is that in which fluorine is substituted for hydro-
gen on the carbon chain. Substitution may be complete to produce the ''perfluoro''
materials (R f ) such as sodium heptadecafluorooctane sulfonate

C 8 F 17 SO 3 Na þ

or they may possess a terminal hydrogen (HR f ) with the general structure

HC n F 2n S

where S may be any of the solubilizing groups discussed. Hydrocarbon groups
may also be encountered in association with linking functionalities such as

R f N ð CH 3 Þ CH 2 CH 2 S

The most commonly encountered commercial fluoro surfactants are prepared by the
electrolytic fluorination of the corresponding alkyl carboxylic acid fluoride or sul-
fonyl fluoride

E = CH 3 ð CH 2 Þ n COF þ HF ! CF 3 ð CF 2 Þ n COF

or

E = CH 3 ð CH 2 Þ n SO 2 F þ HF ! CF 3 ð CF 2 Þ n SO 2 F

The fluorinated products may then be hydrolyzed to the corresponding acid and
neutralized, or functionalized by reaction of the reactive acid fluoride to introduce
linking groups such as the sodium 2-sulfonamidoethane sulfonate

C 8 F 17 SO 2 NHCH 2 CH 2 SO 3 Na þ

Although normal straight-chain hydrocarbon starting materials may be used in the
electrolytic process, some branching will always result, commonly yielding mate-
rials with up to 30% branched isomers.
Perfluorinated alcohols cannot be prepared directly from the electrolytic process
since they require the reduction of the corresponding carboxylic acid to yield struc-
tures of the nature

CF 3 ð CF 2 Þ n CH 2 OH

The presence of the two hydrogens alpha to the hydroxyl is synthetically useful;
however, because the perfluorinated alcohols cannot be effectively used in