Structure of Simpler Organic Compounds. 119 



is obtained which, on treatment with silver hydroxide, 

 yields tartaric acid 



CHBrCOOH CH(OH) CO-OH 



| +2AgOH = 2AgBr+ | 



CHBr-COOH CH(OH) CO-OH 



It can also be obtained synthetically from glyoxal (see 

 p. 106), when this substance is treated with hydrocyanic 

 acid 



/OH 

 CH< 

 CHO 



+ 2HCN = 



C 



HO 



OH 



CH 



The dihydroxy nitrile so produced undergoes the usual 

 reaction on hydrolysis 



/OH /OH 



rtTT/ r*TI/ 



OH^ CH< 



CO-OH 



+ 2NH 3 



CH< CH< 



X CN X COOH 



yielding tartaric acid. This reaction leaves no doubt as to 

 the chemical constitution of tartaric acid. 



Tartaric acid, furthermore, can be converted into 

 succinic acid by reduction. The reagent generally used for 

 replacing the hydroxyl group in hydroxy acids by hydrogen 

 is hydriodic acid 



CH(OH)CO-OH CH 2 CO-OH 



I +2HI= | +I 2 + 2H20 



CH(OH)COOH CH 2 CO-OH 



This is a general reaction, and by the same means lactic 

 acid can be reduced to propionic acid, and malic to succinic 

 acid. 



