THE CHEMICAL PROCESSES IN PLANT RESPIRATION 107 



(II) CeHs— CH< >0 + CeHa— CHO = 2C6H5— COOH. 



Or, briefly stated : 



2C6H5— CHO + O2 = 2C6H5— COOH. 

 It is to be emphasized expressly that the formation of molox- 

 ides is experimentally estabhshed for the processes of autoxida- 

 tion. Engler and Weissberg^ isolated a peroxide of triethyl 



phosphine with the formula j /P(C2H5)3 in the autoxidation 



0/ 

 of triethyl phosphine and thereby proved that the mechanism 

 of triethyl phosphine oxidation assumed by van't Hoff does not 

 exist. The same investigators have shown that, contrary to 

 Traube's view, the autoxidation of triethyl phosphine proceeds 

 smoothly with the complete exclusion of water. A formation 

 of peroxide in the autoxidation of aldehydes was also established 

 by various investigators.- Of the structural formulae which 

 have been proposed for the moloxide of benzaldehyde that of 

 Bach^ proved to be the most reliable: 



CeHs — CH\ yO. 



\o^ 



This very unstable compound with an enormously high 

 oxidation potential changes spontaneously into a stable hydrate 

 form which always has a considerable oxidation potential and 

 which Bodlander thought to be a primary product of oxidation: 



CeHs— C— O— OH 



O 



Moloxides very often change to peroxide hydrates whereby 

 a fixation of water takes place under certain conditions: 



/O .0— OH 



A< I + HoO -> A< 

 \0 ^OH 



1 Engler, A. und Weissberg. Ber. d. chem. Ges. 31 : 3055- 1898. 



2Erlenmeyer. Ber. d. chem. Ges. 27: 1959- 1894; Engler und Wild. Ibid. 30: 1669- 

 1897; Bach. Monit. scient. (IV) 11: 479. 1897; Bodlander. Samml. chem. u. chem.. 

 techn. Vortrage von Arens. 3: 470. 1899. 



» Bach, A. he. cit.; Engler und Wild. Knt. Studien iiber die Vorgange der Autoxyda- 

 tion. 1904. P. 90; Luther und Schilow. Z. f. physikal. Chem. 46: 811. 1903. 



