Identifying Unknown Esters Produced by Fischer Esterification
Introduction
This procedure was performed in order to prepare an ester using an unknown alcohol and unknown acid via Fischer Esterification. Then to identify this unknown ester using gas chromatography. Esters are a derivative of carboxylic acids. In the Fischer approach, an acid is used in order to allow the esterification to occur. Gas chromatography separates compounds by their elution time.
Data and Results The compound in the gas chromatograph exhibited a retention time of 3.68 minutes. This is most near the retention time of n-Butyl benzoate, which is 3.38 minutes. As such, it is likely that the unknown ester is n-Butyl benzoate. This would mean that the acid was benzoic …show more content…
They are formed when an oxygen atom bound to an alkyl group replaces the hydroxyl group in the carboxylic acid. Esters can be formed through a process known as esterification, which starts with a carboxylic acid and an alcohol. The carbonyl carbon in the carboxylic acid acts as an electrophile and the oxygen atom in the alcohol acts as a nucleophile. However, this nucleophile and electrophile are both too weak for the reaction to occur and adding heat fails to catalyze the reaction. One option would be to make the alcohol a stronger nucleophile by converting it to an oxide. However, this would make a carboxylate and regenerate the alcohol because of the acid-base reaction. Another option would be to make the carboxylic acid a better electrophile by adding a NaCl halide but this is too expensive and difficult to be done in a teaching lab setting. Instead, the Fischer approach is used in which the reaction is performed under acidic conditions. The acid first protonates the oxygen in the carboxylic acid making it positively charged. This makes the carbonyl carbon more electrophilic by making it less electronegative because the electrons are being drawn towards the positively charged oxygen atom. The alcohol, acting as a nucleophile, is then able to attack the carbonyl carbon. The acid then protonates one of the OH groups to create water, a good leaving group. The water then leaves and a double bond forms between the carbonyl
Introduction
This procedure was performed in order to prepare an ester using an unknown alcohol and unknown acid via Fischer Esterification. Then to identify this unknown ester using gas chromatography. Esters are a derivative of carboxylic acids. In the Fischer approach, an acid is used in order to allow the esterification to occur. Gas chromatography separates compounds by their elution time.
Data and Results The compound in the gas chromatograph exhibited a retention time of 3.68 minutes. This is most near the retention time of n-Butyl benzoate, which is 3.38 minutes. As such, it is likely that the unknown ester is n-Butyl benzoate. This would mean that the acid was benzoic …show more content…
They are formed when an oxygen atom bound to an alkyl group replaces the hydroxyl group in the carboxylic acid. Esters can be formed through a process known as esterification, which starts with a carboxylic acid and an alcohol. The carbonyl carbon in the carboxylic acid acts as an electrophile and the oxygen atom in the alcohol acts as a nucleophile. However, this nucleophile and electrophile are both too weak for the reaction to occur and adding heat fails to catalyze the reaction. One option would be to make the alcohol a stronger nucleophile by converting it to an oxide. However, this would make a carboxylate and regenerate the alcohol because of the acid-base reaction. Another option would be to make the carboxylic acid a better electrophile by adding a NaCl halide but this is too expensive and difficult to be done in a teaching lab setting. Instead, the Fischer approach is used in which the reaction is performed under acidic conditions. The acid first protonates the oxygen in the carboxylic acid making it positively charged. This makes the carbonyl carbon more electrophilic by making it less electronegative because the electrons are being drawn towards the positively charged oxygen atom. The alcohol, acting as a nucleophile, is then able to attack the carbonyl carbon. The acid then protonates one of the OH groups to create water, a good leaving group. The water then leaves and a double bond forms between the carbonyl