We have observed by means of polarizing light microscopy a novel spontaneous chiral textures with helix axis in the cell plane deep in the smectic phase of achiral p-octyl- and p-octyloxybiphenylcarboxylic acids and close to the nematic-smectic transition of p-octyloxybenzoic acid. The chiral domains appeared in the mesophase, mostly on cooling. The character and the size of the domains depended on the temperature rate. The domains were stable in a large temperature range. The appearance of chiral domains followed a thermal stress. The presence of the spontaneous chiral structures is here explained by a mechanism involving the hydrogen bonding among monomeric molecules, providing as a consequence the presence of both achiral dimeric- and chiral oligomeric molecules in the mesophase.