Mr Fenton, Oxidation in Presence of Iron. 373 



(d) Ferric iron although probably inactive in inducing the 

 initial oxidation has the effect of encouraging the breaking down 

 of the oxidation-product with evolution of carbon dioxide. (Com- 

 pare Ruff's experiments (loc. cit.) and the formation of mesoxalic 

 semi-aldehyde.) 



(e) The oxidizing influence in presence of ferrous iron is 

 selective, certain groups only being prone to attack. Nearly all 

 the results may be primarily expressed by the replacement of 

 hydrogen by hydroxy!, and this action appears to be chiefly con- 

 fined to hydrogen atoms which are directly associated with hydroxyl 

 groups. Hydrogen directly associated with a cyclic nucleus how- 

 ever, as in benzene and pyromucic acid, and with certain unsatu- 

 rated linkages in aliphatic compounds, is also liable to attack. 

 The aldehydic HC : group appears to be remarkably resistant 

 to the oxidation-process in question. 



(f) In some cases the changes could be most easily explained 

 by the supposition that non-hydroxylic hydrogen atoms are simply 

 withdrawn, as for example in the oxidation of tartaric acid to 

 dioxymaleic acid. This explanation in the latter instance although 

 satisfactory in other respects would, according to the hypothesis of 

 van 't Hoff and Wislicenus, necessitate the formation of a fumaroid 

 derivative, whereas a maleinoid form actually results. This question 

 has recently been investigated by W. F. Cooper of Clare College 

 and the author, and their experiments shew that the di-acyl 

 derivatives of tartaric acid do not appear to lend themselves to 

 the oxidation-process in question, so that the hydroxylic hydrogen 

 atoms would appear to be essential. 



Incidental Observations. 



In the process of working out the problems above described 

 a large number of interesting observations, not directly connected 

 with the primary objects, have been made, and in following up 

 some of these side issues results of considerable importance have 

 been obtained. It has been considered advisable in the present 

 communication to include a very brief account of these in order to 

 give an idea of the extent of ground which has been covered. 



Esterification by Ethyl Ether. [Fenton and Gostling, Trans. 

 Chem. Soc. 1898. 554.] In studying the properties of dioxymaleic 

 acid it was found that hydrogen bromide acted in an interesting 

 manner, and various solvents were employed for the reaction. In 

 using perfectly pure, dry ethyl ether an unexpected result was ob- 

 tained, the product being ethyl dioxymaleate. An excellent yield 

 is obtained in this way, and the observation was extended to other 



27—2 



