the aldehydic group also can be a c 1 to c 14 straight chain or branched aldehydic group the aldehydic group can be a c 1 to c 12 straight chain or branched aldehydic group such as for example acetaldehyde propionaldehyde butyraldehyde valeraldehyde hexanal heptanal octanal nonanal decanal undecanal dodecanal r can be a c 1 to c 10 straight chain or branched aldehydic group a c 1 to c 8 straight chain or branched aldehydic group or a c 1 to c 6 straight chain or branched aldehydic group r further can be a carboxylate group of a dicarboxylic acid or other carboxylic acid e g a hydroxyl acid to form a retinyl ester some of which are also referred to as retinoyl esters the carboxylic acid can be for example oxalic acid ethanedioic acid malonic acid propanedioic acid succinic acid butanedioic fumaric acid butenedioic acid malic acid 2 hydroxybutenedioic acid glutaric acid pentanedioic acid adipic acid hexanedioic acid pimelic acid heptanedioic suberic acid octanedioic azelaic acid nonanedioic acid sebacic acid decanedioic acid citric acid oxaloacetic acid ketoglutaratic acid or the like r can also be an alkane group to form a retinyl alkane ether suitable alkane groups include for example c 1 to c 24 straight chain or branched alkyls such as for example methane ethane butane isobutane pentane isopentane hexane heptane octane or the like for example the alkane group can be a linear iso sec tert or other branched lower alkyl ranging from c 1 to c 6 the alkane group also can be a linear iso sec tert or other branched medium chain length alkyl ranging from c.