Esterification overall reaction model

Three modeling approaches can be applied to the esterification reaction kinetics the molecular species model, the functional group model, and the overall reaction model. These are schematically illustrated in Scheme 4.5. 

Fiery1 252-254) studied only the last stage of the reactions, i.e. when the concentration of reactive end groups has been greatly decreased and when the dielectric properties of the medium (ester or polyester) no longer change with conversion. Under these conditions, he showed that the overall reaction order relative to various model esterifications and polyesterifications is 3. As a general rule, it is accepted that the order with respect to acid is two which means that the add behaves both as reactant and as catalyst. However, the only way to determine experimentally reaction orders with respect to add and alcohol would be to carry out kinetic studies on non-stoichiometric systems. 

Two overall reactions will be considered in the kinetic model esterification of acetic acid with methanol and esterification of hydrogen iodide to methyl iodide. The overall reactions can be written as follows ... 

The overall efficiency of these nonmolecular bimetallic sysems to promote phosphate ester hydrolysis was illustrated with ApA as RNA model (0.1 mM) hydrolysis occurred with a mixture of LaCls and FeCls (10 mM each) to more than 70% at 50°C and neutral pH in 5 min (351). The products of the reaction included adenosine and 2 -and 3 -monophosphate adenonsine, indicating that the mechanism involved a first trans-esterification step by the vicinal 2 -OH of ribose. With the same mixture of metal ions, the DNA model TpT (0.1 mM) (Fig. 18), left, B = thymine) was converted to thymidine and 3 - and 5 -monophosphate th5miidine with 36% of conversion in 24 hr at 70°C at neutral pH. The important point is the notion of cooperativity between the two metals. 

Example 2.4 Give the mechanism of esterification reaction with certain exchanger catalyst and mathematically model the overall heterogeneous reaction. 

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