Introduction Measuring Relative BF3 Affinity by Ligand Exchange in Solution

1 Introduction Measuring Relative BF3 Affinity by Ligand Exchange in Solution 

Considering the complexity of the gas measurement system and its coupling to the calorimeter, a simpler method related to titration calorimetry is also proposed. Here, the source of BF3 is the addition compound with diethyl ether, a liquid easier to handle than gaseous BF3. The reaction studied is now 

We have followed Brown and Horowitz [9] in choosing nitrobenzene as the solvent. Indeed, nitrobenzene is much less volatile than CH2CI2. Moreover, a very good relationship has been established [8] between the BF3 affinities in dichloromethane and in nitrobenzene. 

The experiment proposed corresponds to a variant of titration calorimetry. The titration is done by stepwise (discontinuous) injections of small increments of a pyridine solution into a given amount of the BF3 complex in solution, until a complete reaction. The amount of complex is calculated to give 5-10 injections before complete displacement. The enthalpy of dilution should be taken into account by measuring a blank injection of pyridine in nitrobenzene. 

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