Abstract: Compounds of the formula ##STR1## in which; X represents a straight chain hydrocarbyl group containing from 8 to 17 carbon atoms;Y represents H or the group--CH.dbd.NOH, andZ represents H or the group--CH.dbd.NOH or the group--CPh.dbd.NOH,provided that at least one of Y and Z represents H; or such compound containing at least one electronegative substituent in the aromatic ring, may be prepared from anacardic acid and its analogues, and are useful for the extraction of copper from acidic aqueous solution. Cardanol, which has the formula ##STR2## where n=0, 2, 4 or 6 is recovered from cashew nut shell liquid containing cardol and other dihydric phenols by reacting the dihydric phenols in the CNSL with an aldehyde while leaving the cardanol substantially unreacted, and vacuum distilling the cardanol from the reaction mixture.