Manchester Memoirs, Vol. Ixiv. (1920), No, 3 



III. — Latent polarities of atoms and mechanism of 

 reaction, with special reference to carbonyl compounds.. 



Bv Professor Arthur Lapworth, D.Sc., F.R.S. 



(Bead March 16th, 1920. Received for publication March 29th, 1920.) 



The conception introduced by J. J. Thomson that the 

 conventional valency "bond" between two atoms corresponds 

 with the field between two opposite electrical charges situated 

 on the atoms has been utilised by Ramsay, Fry and many 

 other chemists to aid in accounting for phenomena of the most 

 diverse character, such as the laws of substitution in the' 

 benzene series and the decompositions of citric acid and of 

 aceto-acetic acid (Fry, Zeitsch. physikal. Chemie, 191 1 , 76,. 

 385, 398, 591; /. Amer. Chem. Soc, 1908, 30, 34; 1912, 34, 

 664; 1914, 36, 284, etc.; 1915, 37, 855, etc.; 1916, 38, 1323, 

 etc. Hancke and Koessler, /. Amer. Chem. Soc., 191 8, 40, 

 1726. Compare also Vorlander, Ber. d. Deutsch. Chem. 

 Gesellsch., 1919, 52 [B], 263.) 



The writer has for a number of vears used for his own 

 guidance, and to a certain extent in teaching, a system of 

 representing the activities of carbon compounds which involves 

 the labelling of the atoms in the molecule with + and - signs, 

 and with results which do not at first sight differ greatly from 

 the figurations developed by Fry and others. In one very 

 important particular he is in agreement with Noyes, Fry and 

 others of this school in holding that the terms " positive " and 

 " negative" have in the past been widely misapplied to many 

 atoms and groups ; for example, it has been customary to- 

 term -NH 2 a "positive" group, and acetyl CH 3 'CO- a 

 " negative" group, while in point of fact when these groups 

 are united, forming acetamide, CH 3 'CO-NH 2 , and set in 

 competition with one another for the components of the water- 

 molecule, it is the acetyl group which attracts the truly negative 

 hydroxyl and the -NH 2 group which attracts the positive- 

 hydrogen, 



H--OH I H OH 



I and l 

 NHo CO.CH, 



and 

 NH 2 — CO.CH 



+ • 



October 22nd, 1Q20. 



