MIXED COMPOUNDS 75 



Malic Acid {Mono-hydroxy-succinic Acid) 



We shall now consider three acids which are widely distributed 

 in nature occurring either free or as salts in many of our common 

 fruits. They all belong to this same group of hydroxy-acids 

 to which lactic acid belongs. The first two, malic and tartaric, 

 are derivates of succinic acid. 



When succinic acid is converted into mono-hrom-succinic acid, 

 this, by replacing bromine with hydroxyl by means of silver 

 hydroxide, Ag(OH), yields malic acid, thus proving it to be 

 mono-hydroxy- succinic acid. The reactions are as follows : 



CH2-COOH CHBr-COOH CH(OH)-COOH 



I +Br2->HBr+| 4.Ag(0H)->| 



CH2-COOH CH2-COOH , CH2-COOH 



Succinic acid Mono-brom- Malic acid 



succinic acid Mono-hydroxy- 



succinic acid 



In nature malic acid is found in many acid fruits such as 

 apples, cherries, gooseberries, raspberries, strawberries, currants, 

 pineapples and grapes, and in seeds of some other plants, e.g. 

 pepper and parsley and in unripe berries of the mountain ash. 

 Its name is derived from its being found in apples. It is ob- 

 tained commercially from the mountain ash berries. It is a 

 solid substance readily soluble in water and melts at 100*^ C. 



The malic acid found in nature is levo-rotatory in dilute solu- 

 tions. The dextro-rotatory form and also the inactive form are 

 both known. The existence of these three stereo-chemical 

 isomers is in accord with the theory just discussed in regard 

 to the asymmetric carbon atom, one of the carbon atoms in 

 malic acid being asymmetric. 



OH 



I 

 H-C-COOH 



CH2 - COOH 



Malic acid 



