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Lab #2: Hydrolysis of 1-Chlorobutane

Andrea C.D Elia 300039408 Grace McKale 300090874 September26, 2019 TA: Omid Daneshfar CHM 2123

Introduction:

Part A:

Studying the ratę of a reaction helps ensure the reaction is safe and useful in an industrial setting. Studying the kinetics of a particular reaction also helps further the understanding of the mechanism and all the steps required. In Part A, the kinetics of the hydrolysis of alkyl halide is studied. Two electrophiles were compared to show the effects of different leaving groups in this reaction which proceeds by the mechanism of bimolecular nucleophilic substitution (Jug, U et al.) also known as Sn2.

An Sn2 reaction is a reaction in which the nucleophilic attack and the dissociation of the leaving group happens in one concerted step. The electrophile must have either a methyl, primary or secondary carbon alpha in order for the Sn2 reaction to take place. In the case of 1-bromobutane or 1-chlorobutane, the carbon alpha is primary. This reaction is also biomolecular and therefore the ratę is dependent on both the concentration of the electrophile and the nucleophile. There are also many factors that can affect the ratę of the reaction such as nucleophilicity, steric congestion around the electrophile and the leaving group.

In the laboratory, the reaction between potassium hydroxide and either 1-chlorobutane or 1-bromobutane was studied. The effect of the chloride and bromide as leaving groups and the reaction order was then determined by comparing the ratę of the reaction which was measured by determining the concentration of unreacted potassium hydroxide and alkyl halide at different time intervals. Since the ratio of reagents is 1:1 in this reaction, the concentration of KOH also corresponds to the concentration of electrophile. An aliquot from the reaction at different times was titrated with hydrochloric acid to determine the concentration of the reactants at that specific time. Phenolphthalein was the indicator used and signaled when the solution was neutralized.

The goal of this experiment was to determine the effect of the leaving group on the kinetics of the reaction. This can be done by graphical analysis of each of the electrophiles. By graphing the electrophiles, the experimental order of the reaction is found and then the slopes of both electrophiles are compared to determine the most effective leaving group. The slope also represents the value k which is a ratę constant that can then be used in the ratę equation rate=k[Nu][R-X] . The higher value of k, the faster the reaction will proceed.