EFFECTS OF ALTERATION OF STRUCTURE 305 



I. Change in position of a group: a single group is moved from one po- 

 sition in a molecule to another position. 



A A 



I I 



R-CH2-CH-CH2-R' R-CH-CH2-CH2-R' 



OH OH 



I NO, I NO, 



NO, 



X0« 



II. Replacement of a group: a single group is removed and another group 

 put in the same position. 



III. Addition or removal of a group: a group is removed from the mol- 

 ecule (usually replaced by H) or a new group is added (usually replacing 

 an H). 



R — CH2 — CH2 — R' R — CH2 — R' 



R-COO~ R-COOCH3 



OH OH 



I NO. 1 



Y V 



NO2 NO2 



It is our immediate problem now to determine what physical and chemical 

 properties of molecules may be modified by such changes in structure. 



