Setting Reduced Keratin Fibres with 1‐Fluoro‐2,4‐dinitrobenzene

Keratin fibres, when extended, reduced, and allowed to react with 1‐fluoro‐2,4‐dinitrobenzene under either acid or alkaline conditions at 40d̀c, acquire a permanent set. Unreduced fibres and fibres reduced before extension are not permanently set. The effect may be caused by steric hindrance of mutual movement of protein chains by the large 2,4‐dmitrophenyl group, or by hydrogen bonding between the nitro groups and ambient protein chains; or alternatively reaction with 1‐fluoro‐2,4‐dinitrobenzene may alter the stability of the hydrogen‐bonded protein system. The experiments seem to confirm earlier results which suggested that on extension certain cystine disulphide residues in the fibre become accessible to attacking reagents, and that these residues, previously inaccessible at 40d̀c, are those which are essentially involved in permanent setting.