IOWA ACADEMY OP SCIENCE 
137 
VELOCITY COEP'PICIENTS OP THE REACTION BETWEEN ETHYL IODIDE 
AND SILVER NITRATE IN ETHYL AND METHYL ALCOHOL 
AND MIXTURES OP THESE SOLVENTS. 
BY J. N. PEARCE AIN’D O. M. WEIGLE. 
HISTORICAL. 
The study of chemical reactions in various solvents is one that has been 
occupying the attention of chemists for a long time, for by this means it is 
thought that we may in time gain a closer insight into the mechanism of chem- 
ical reactions in general. A reaction frequently studied is thdt between alkyl 
halides and silver nitrate. 
Burke and Donnan’ made an extensive study of a number of reactions in- 
volving alkyl iodides and silver nitrate in ethyl alcohol. They found the 
reaction to be “pseudobimolecular” in character, i. e., the velocity coefficients 
of the simple bimolecular equation vary (increase) considerably with the initial 
concentration of the reacting substances, although it remains fairly constant 
during the course of any particular reaction. 
They found also that the velocity coefficient, k, increases with increasing 
initial concentration of silver nitrate when the nitrate and the iodide are present 
in equivalent proportions. Using the same initial concentrations of silver 
nitrate and varying the proportions of ethyl iodide, the constants, k, are found 
to decrease with increasing concentration of ethyl iodide. When the iodide 
is kept constant, the velocity coefficients increase with increasing initial con- 
centrations of silver nitrate. They were not able to explain the variation in 
the values of k. 
The velocity coefficients in ethyl alcohol, using 0.025N, equivalent solutions of 
silver nitrate and alkyl iodides, were found to decrease in the following order: 
isopropyl, ethyl, n-propyl, methyl, n-butyl, isoamyl, isobutyl. 
The velocity coefficients of the four iodides, methyl, ethyl, n-propyl, and 
n-butyl, were likewise determined in methyl alcohol, using 0.025N equivalents 
of iodide and silver nitrate. 
In every case the velocity coefficients were greater in methyl than in ethyl 
alcohol, the ratio ‘'MeOH /‘'EtOH being approximately equal to 2. 
An addition of water to the extent of ten per cent produced only a slight 
increase in the value of k. The addition of benzene (10%), a non-dissociating 
solvent, gave a slightly lower value for k. 
In a second paper, Burke and Donnan^ give the results of further study of the 
reaction of ethyl iodide and silver nitrate in ethyl alcohol. Their purpose was 
to study the effect of the reaction products upon the velocity coeflBcients, and 
to determine which is the disturbing factor. Experiments proved that this 
disturbance is not due to ethyl nitrate, or ether, while nitric acid slightly re- 
tard the speed. The velocity coefficients are increased by the addition of both 
iJ. Chem. Soc. 85, 555 (1904). 
^Z, physik. Chem., 69, 148 (19 0 9). 
