November 23, 1917] 



SCIENCE 



497 



Cl l-CN + HH 0H = 



H H Cl + HO h CN, 



I-l CN + HH 0H = 



HO l-I + H H CN. 



Tetrabromomethane and tetraiodomethane, 

 when hydrolyzed, give bromoform and iodo- 

 form, respectively : 



Br3C h Br + HOH = 



BrjG — + H + HO h Br, 



IjC f- I + HOH = 



I3C h H + HO hi. 



Iodine monoehloride reacts as follows: 



l-\ C1-I-H+ — OH = HO — -1-I + H + — Cl. 



In fact, there is no difficulty in finding 

 among organic compounds countless cases 

 in which the polarity manifests itself 

 clearly during chemical changes. Thus, in 

 the case of alkyl cyanides, RON, it may be 

 asked what indication there is in the for- 

 mula itself to lead chemists to predict, un- 

 erringly, that the products of hydrolysis of 

 such a compound are alwaj'S ammonia and 

 a carboxylic acid. Pure speculation would 

 suggest that at least four different sets of 

 products are possible : 



(a) EC (OH) 3 andNHj; 



( 6 ) ECH ( OH ) , and NH,OH ; 



(c) ECH.OH and NH(OH),; 



(d) ECH3 and N( OH) 3. 



But the substances expressed under (a) are 

 the only ones ever realized. That this de- 

 cision is not inherent in the formula is 

 emphasized all too forcibly by the fact that 

 these four sets of products are the very ones 

 which beginning students offer to explain 

 the hydrolj'sis of an alkyl cyanide. In 

 terms of the electron conception valence, 

 the explanation lies in the fact that the 

 nitriles are polar compounds of the for- 

 mula: 



+ — 



EC 4- — N 



4- — 



In this connection, some recent experi- 

 ments on mercury dialkyls carried out with 

 Mr. "Werner in our laboratory have led to 

 the observation that, upon complete hydro- 

 lysis in the presence of acetic acid, the 



products formed are metallic mercury, an 

 alcohol, and a hydrocarion. At about 200°, 

 mercury diethyl decomposes to give mer- 

 cury and butane. This dissociation im- 

 plies that the mercury atom in these dia- 

 lkyls either possesses, or readily assumes, 

 the condition of reduction which it has in 

 the metallic state, viz., with an equal num- 

 ber of positive and negative "charges." 

 This suggests, also, that the two ethyl 

 groups may be one negative and the other 

 positive : 



" -I CoHs ■ 



+ C,H, H C=H,. 



When mercury diethyl is heated with 

 acetic acid, further evidence in support of 

 this inference is furnished ; a quantitative 

 j'ield of metallic mercury is found, and in 

 addition, ethane and ethyl alcohol (or acetic 

 ethyl ester). These changes may be ex- 

 pressed in terms of the electron conception 

 of valence as follows : 



+ C,H, , H-f — 0H_ 

 ^^ H- — C,H. "♦" H H OH — 



Hg + ^^+lS^+HA 



If these reactions of mercury diethyl are 

 compared with those of zinc alkyls and of 

 oxygen alkyls, the significance of the state- 

 ment that the polar characteristic of com- 

 pounds becomes manifest during chemical 

 changes will be apparent. Thus, zinc 

 alkyls are hydrolj^zed to give exclusively 

 zinc hydroxide and a hydrocarbon; oxygen 

 alkyls give exclusively alcohols. 



+ — C,H, H -f- — OH _ 

 ^'^ -f — CHs + H -I- — OH — 



7 4- — OH , H-I- — C.,H„ 

 ^ 4- — OH + H -1- — C-Hj, 



— 4-C,H, , H4-— OH_ 

 " — 4- C.H5 ■*" H 4- — OH — 



n— + H,HO — 4- a.H„ 

 ^ hH"''HO h Q,H.. 



If, therefore, the atoms in compounds 

 may function positively or negativelj^ in 

 general a univalent atom, A, maj^ be repre- 

 sented bj' two electronic sjTnbols, A -\- and 



