Findeco’s LAS/BAS (Sulfonic Acid) is a product resulted from sulphonation reaction of Alkylbenzene as following :


If molecule R - O is a branched chain the suphonated product becomes
a branched alkylbenzene sulphonic acid (BAS, hardtype)

while the molecule R - O is bonded in linear configuration, the sulphonated product will be a linear alkylbenzene sulphonic acid (LAS, soft type)