CHAPTER IX 

 ORGANIC ACIDS, ACID SALTS, AND ESTERS 



ORGANIC acids, either in free form, or partially neutralized with 

 calcium, potassium, or sodium, forming acid salts, or combined 

 with various alcohols in the form of esters, are widely distributed 

 in plants. They occur in largest proportions in the fleshy tissues 

 of fruits and vegetables, where they are largely responsible for the 

 flavors which make these products attractive as food for men and 

 animals. But organic acids and their salts are also found in the 

 sap of all plants, and undoubtedly play an important and definite 

 part in the vital processes of metabolism and growth. 



CHEMICAL CONSTITUTION 



All organic acids contain one (or more) of the characteristic 



O 

 acid group, COOH, or C^ , known as " carboxyl." This 



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group is monovalent, and in the simplest organic acid, formic acid 

 (H2CO2), it is attached to a single hydrogen atom, thus, H-COOH. 

 In all other monobasic acids, it is attached to some other monova- 

 lent group, usually an alkyl radical, i.e., a radical derived from an 

 alcohol and containing only carbon and hydrogen (as methyl, 

 CHs, ethyl, C2Hs, butyl, C4H 9 , acryl, C2H3, etc.). Hence, the 

 general formula for all monobasic organic acids is R- COOH, the R 

 representing any monovalent radical. In the simplest dibasic 

 acid, oxalic (H2C2O4), two carboxyl groups are united to each 

 other, thus, HOOC-COOH; but in the higher members of the 

 series, the two characteristic acid groups are united through 

 one or more CH2 groups, or their oxy-derivatives (as 

 HOOC CH 2 COOH, malonicacid ; HOOC CH 2 CH 2 - CH 2 COOH, 

 glutaric acid; HOOC .CHOH-CH 2 - COOH, malic acid, etc.). 

 Polybasic acids, containing three or more carboxyl groups, 



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