ESTERIFICATION AND HYDROLYSIS

Term Paper Title	ESTERIFICATION AND HYDROLYSIS
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ESTERIFICATION AND HYDROLYSIS

Experiment #1: Methyl Benzoate by Fisher Esterification

Post � Lab

Organic Chemistry II Lab � Section 7515

February 25, 2004

INTRODUCTION

The Fischer esterification reaction reaches equilibrium after a few hours. This equilibrium can be shifted by adding more of the acid or of the alcohol. The mechanism of the reaction involves initial protonation of the carboxyl group, followed by attack by nucleophilic hydroxyl, a proton transfer, and finally loss of water followed by loss of the catalyzing proton to give ester. All these steps are also reversable.

The purpose of this experiment is to obtain methyl benzoate through fisher esterification by using benzoic acid, methanol, and concentrated sulfuric acid.

EXPERIMENTAL PROCEDURE

10g of pre-weighed benzoic acid and 25ml of methanol were placed into the 125ml round bottomed flask. 3ml of concentrated sulfuric acid was added to the flask very carefully after the mixture cooled off (in the ice bath) to approximately room temperature and the whole mixture was then swirled. After the reflux condenser was attached, the boiling chip was added, the mixture was refluxed for approximately 1 hour. The solution was then cooled and was poured into a separatory funnel that contained 50ml of water. The flask was rinsed with 35ml of ethyl ether, and this was then added to the separatory funnel. The separatory funnel was shaken well and the water layer (containing sulfuric acid and methanol) was drained off. The ether in separatory funnel was washed with 25ml of water and then with 25ml of 0.5M sodium bicarbonate (to remove unreacted benzoic acid). The funnel was shaken well again with frequent release of pressure (inverting the separatory funnel and opening the stopcock) until no reaction was visible and the bicarbonate layer was drained off into a beaker. The ether layer in separatory funnel was washed with saturated sodium chloride solution and dried with anhydrous calcium chloride in Erlenmeyer flask. After about 10 minutes, the dry ether solution was poured into a flask, while the drying agent was washed with 5ml of ether, and poured out again. The ether was removed by evaporation. When evaporation was over, methyl benzoate was poured into 50ml round bottomed flask for the simple distillation process. The boiling point of ester is very high, around 199 degrees Celsius. This high temperature may cause the condenser to crack. The material was collected into three pre-weighed bottles (the first two bottles had around 2-3ml, while the third had the rest of the distilled solution) when there was boiling above 190 degrees Celsius.

IR analysis was done on the three collected samples.

DATA

MW(g/mol)

BP(degrees C)

MP(degrees C)

Density(g/cm^3)

Benzoic acid

122.12

122

Methanol

32.04

64.6

0.791

Methyl benzoa...

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