400 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



series of compounds, all of which might be regarded as 

 derived from a compound radical, which they proposed 

 to call BENZOYL (loc. tit. p. 279). This radical combined 

 with hydrogen to form oil of bitter almonds, with oxygen 

 and hydrogen to form benzoic acid, with chlorine, bromine, 

 iodine, sulphur and cyanogen to form benzoyl chloride, 

 bromide, iodide, sulphide and cyanide. These compounds 

 may by represented by the following formulae : l 



BENZOYL = C 7 H 8 O. 



Oil of bitter almonds = benzoyl hydride . . = C^HgO *H 



Benzoic acid = benzoyl hydroxide . . = CyHgO'OH 



Benzoyl chloride = C 7 H B OC1 



Benzoyl cyanide - C 7 H 5 O'CN 



Wohler and Liebig also prepared : 



Benzamide . = C 7 H 5 O-NH 2 



Ethyl benzoate = C 7 H 5 O'OC 2 H 5 



Benzoin, a solid having the same composition as 

 oil of bitter almonds, but now regarded as a 

 polymer (C 7 H 5 OH) 2 = C 14 H 12 O 2 



Berzelius was delighted with the discovery made by 

 Wohler and Liebig. The compound radicles which had 

 been studied hitherto had been binary compounds of two 

 elements, e.g., cyanogen, CN, ammonium, NH 4 ; jthe 

 benzoyl group was the first example of a compound radical 

 containing three elements, which nevertheless showed very 

 many of the properties of a simple substance. In a well- 

 known letter to Wohler and Liebig, dated from Stockholm, 

 Sept. 2, 1832, and published at the conclusion of their paper 

 (Liebig's Ann. der Pharm., 1832, 3, 282-287), Berzelius 

 writes : 



"The facts that you have ascertained suggest so many 

 considerations, that they may well be regarded as the begin- 

 ning of a new day in vegetable chemistry. I would therefore 

 propose, to call the first example of a compound radical 

 containing more than two substances Proin (from Tr/awi', the 



1 Wohler and Liebig doubled these formulae and wrote benzoyl = 

 C 14 H 10 O 2 ; chlorobenzoyl (benzoyl chloride) = C 14 H ]0 O 2 C1 2 , etc. 



