Chemical Kinetcs – the Hydrolysis of Pna Ester

1424 Words Sep 22nd, 2015 6 Pages
“Chemical Kinetcs – The hydrolysis of PNA Ester”

Introduction: Reaction of a compound with water can result in a splitting, or lysis, of the compound into two parts. Organic molecules containing a group of atoms called an ester can be hydrolyzed by water to form a –COOH group (carboxylic acid) and an HO-- group (alcohol) as follows:
RCOOR’ + H2O ( RCOOH + HOR’

This reaction is spontaneous for almost all esters but can be very slow under typical conditions of temperature and pressure. The reaction occurs at a much faster rate if there is a significant amount of base (OH-) in the solution. In this lab experiment, the rate of this reaction will be studied using an ester called para-nitrophenyl acetate (PNA), which produces an alcohol,
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|Table 1 |
|Varying Exp |Test Tube|PNA [45mg/0.5L] |(PO4)3- Buffer| |H2O |Catalyst | | | |
|1.5x[PNA] |2 |3 |7 |2 |0 |- |- |- |- |
|1/2 [PNA] |3 |1 |7 |2 |2 |- |- |- |- |
|Imidazole |4 |2 |7 |2 |0 |Imidazole |0.025 |1 |0.005 |
|Super (10x) Imidazole|5 |2 |7 |2 |0 |Super (10x) Imidazole|0.25 |1 |0.05 |
|2-Me. Imid. |6 |2 |7 |2 |0 |2-Me. Imid. |0.025 |1 |0.005 |
|4-Me. Imid. |7 |2 |7 |2 |0 |4-Me. Imid. |0.025 |1 |0.005 |
|Acidic pH 6.5 |8 |2 |6.5 |2 |1 |- |- |- |- |
|Basic pH 7.5 |9 |2 |7.5 |2 |1 |- |- |- |- |
|Basic pH 8.0 |10