Caproic Acid Synthesis
Introduction In this lab, caproic acid was synthesized in a multi-step process that involved the synthesis of three intermediates – diethyl n-butylmalonate, potassium n-butylmalonate, and n-butyl malonic acid respectively. An IR was used to characterize the starting material, n-bromobutane, and the first intermediate, diethyl n-butylmalonate; while IR and NMR were used to characterize the final product, caproic acid.
Reactions, Mechanism and Theory
Caproic acid a.k.a n-hexanoic acid is a carboxylic acid derived from hexane which has the general formula C5H11COOH. It is a colorless oily liquid with a really pungent odor associated with goats. Caproic acid was synthesized in a multi-step process which produced three intermediates - diethyl n-butylmalonate, potassium n-butylmalonate, and n-butyl maonic acid. The synthesis of caproic acid involved alkylation, saponification, and decarboxylation reactions.
The first intermediate, diethyl n-butylmalonate – a diethyl ester of malonic acid – was synthesized via an alkylation reaction. Alkylation reactions involve the formation and alkylation of an enolate. In this lab, NaOEt, a strong base was used to pull off one of the most acidic α-hydrogens of the carbonyl ester – diethylmalonate – to form an enolate. In order to alkylate the alpha position which now has a negative charge, the enolate was used to attack an alkyl halide, 1-bromobutane via Sn2 mechanism. The mechanism for the above reaction is shown below:
The second intermediate, potassium n-butylmalonate, was synthesized by saponification of the first intermediate, diethyl n-butylmalonate, with potassium hydroxide. The hydrolysis of diethyl n-butylmalonate resulted in the formation of potassium n-butyl malonic acid by losing the ethoxy group (-OCH2CH3) from both sides of the carbonyl ester. Further deprotonation of the formed acid by -OCH2CH3 forms a carboxylate, potassium n-butylmalonate. The mechanism for the above process is shown below:
N-butyl
Reactions, Mechanism and Theory
Caproic acid a.k.a n-hexanoic acid is a carboxylic acid derived from hexane which has the general formula C5H11COOH. It is a colorless oily liquid with a really pungent odor associated with goats. Caproic acid was synthesized in a multi-step process which produced three intermediates - diethyl n-butylmalonate, potassium n-butylmalonate, and n-butyl maonic acid. The synthesis of caproic acid involved alkylation, saponification, and decarboxylation reactions.
The first intermediate, diethyl n-butylmalonate – a diethyl ester of malonic acid – was synthesized via an alkylation reaction. Alkylation reactions involve the formation and alkylation of an enolate. In this lab, NaOEt, a strong base was used to pull off one of the most acidic α-hydrogens of the carbonyl ester – diethylmalonate – to form an enolate. In order to alkylate the alpha position which now has a negative charge, the enolate was used to attack an alkyl halide, 1-bromobutane via Sn2 mechanism. The mechanism for the above reaction is shown below:
The second intermediate, potassium n-butylmalonate, was synthesized by saponification of the first intermediate, diethyl n-butylmalonate, with potassium hydroxide. The hydrolysis of diethyl n-butylmalonate resulted in the formation of potassium n-butyl malonic acid by losing the ethoxy group (-OCH2CH3) from both sides of the carbonyl ester. Further deprotonation of the formed acid by -OCH2CH3 forms a carboxylate, potassium n-butylmalonate. The mechanism for the above process is shown below:
N-butyl
References: Reagent table http://www.chemblink.com/products/133-08-4.htm