CHEMICAL PROPERTIES 



Table 1-1 

 Ionization Constants" for Halogen-Substituted Acids 



<■ These values have been corrected as far as possible for 37° and an ionic strength 

 of 0.15. 



lity considerations is the fact that both iodoacetic and bromoacetic acids 

 tend to concentrate somewhat in an oil phase; thus the partition coefficients 

 are 2.90 for iodoacetic acid and 15.6 for bromoacetic acid using olive oil 

 (Bodansky and Meigs, 1932), and 2.4 for bromoacetic acid using octanol 

 (Collander, 1951). 



Reactions with Thiols 



By 1910 it was recognized that iodoform is broken down in the tissues 

 and by cell-free preparations. Thunberg (1911 b) demonstrated that iodine 

 is set free from iodoform in the presence of thiols and stated, "... Bin ich 

 zu der Auffassung geleitet worden, dass die Giftwirkung einiger Stoffe — der 

 bromsauren und jodsauren Sake — moglicherweise dadurch zu erkldren ist, 

 dass sie mit der Snlfhydrylgruppe reagieren.'' * It was also known by organic 

 chemists that halogen acids react with SH groups, as in the Klason reac- 

 tion for the synthesis of thiodiglycolate. However, it was not until the 

 importance of iodoacetate in muscle and yeast metabolic studies was rec- 

 ognized that interest in such reactions was stimulated. 



* "I have been led to the concept that the toxic actions of certain substances 

 - the salts of bromo and iodo acids - can be explained by their reaction with sulf- 

 hydryl groups." 



