Theoretical study of acid acetylation of ethylamine
Date
2014
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Abstract
Abstract. The acetylation of amines is one of the most frequently used transformations in
organic synthesis as it provides an efficient and inexpensive means for protecting amino
groups in a multistep synthetic process. Acetylation of amine is a nucleophilic substitution
reaction. This reaction can be catalyzed by Brönsted acid. In the mechanism, the acetic
anhydride first accepts a proton at the carbonyl oxygen and this change enhances the positive
charge on the carbonyl carbon. This protonation facilitates the successive addition of amine at
the position to form a tetrahedral intermediate, determining step of the rate of the reaction.
Computational method to study the reaction using acid catalysis [1] and an experimental work
[2], agreed that this reaction takes place with the formation of a tetrahedral intermediate. A
theoretical study of acid acetylation of ethylamine from the analysis of intermediate of the
reaction was carried out. Geometries of all species involved in the acetylation were made and
identified. All of the geometry optimizations were performed by the method at the DFT -
Density Functional Theory [3] with B3LYP level of theory and was adopted the 3-21+G*
basis set. Energies of all reagents and products and the energy of activation for the reaction
were calculated using the AM1- Austin Model 1 method. Following the same procedure it
was identified the geometric parameters and energy of intermediate. All the calculations were
executed using Gaussian 09 software package. The calculations show 33.89 kcal/mol of
energy for the tetrahedral intermediate and the activation energy was 9.07 kcal/mol. It was
observed a marked consistency between the theoretical results and bibliographic data, which
validates the use of theoretical methods DFT and AM1 as tools for kinetic studying the
reaction of acetylation of ethylamine.
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Keywords
Acetylation, Ethylamine, AM1, DFT
Citation
XL Congreso de Quìmicos Teòricos de Expresiòn Latina.2014
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