%0 Journal Article
%T A Proposed Stereochemical Mechanism for the Improved Preparation of Maleic Anhydride Cycloadduct of CLA
%A Jieyu He
%A Jiashu Liao
%A Junyan Qu
%J Computational Chemistry
%P 144-160
%@ 2332-5984
%D 2021
%I Scientific Research Publishing
%R 10.4236/cc.2021.93009
%X The fatty acid derivatives, prepared from renewable natural oils, can be used as highly promising and potential substitutes for petrochemicals. The study of process improvement and stereochemical mechanism for preparing these derivatives would be beneficial for their industrial production. Conjugated linoleic acid (CLA) containing 9<em>cis</em>-11<em>trans</em> (9<em>c</em>, 11<em>t</em>) and 10<em>trans</em>-12<em>cis</em> (10<em>t</em>, 12<em>c</em>) isomers was prepared from <em>Salicornia herbacea</em> seed oil. Maleic anhydride cycloadduct of CLA (MAC) was prepared by an improved process, and it was characterized by FTIR, <sup>1</sup>H and <sup>13</sup>C NMR, <em>etc</em>. A new method to calculate conformers-ratio of CLA or MAC was also developed. Furthermore, the stereochemical mechanism for the improved preparation of MAC was proposed primarily by the calculation method above. The following observations were made: 1) The yield of MAC could reach as high as 96.7% under mild reaction conditions and with an easy and efficient product separation; 2) The <em>trans-trans</em> CLA in the<em> s-cis</em> conformation acted as a predominant reactant to <em>Diels-Alder</em> [4 + 2] cycloaddition of maleic anhydride, which was the main reaction occurred simultaneously with catalytic configurational isomerizations of CLA in one step; 3) From all studied CLA conformers, the most stable conformation was the s-trans conformation of trans-trans CLA, while the <em>s-cis</em> conformation of <em>trans-trans</em> CLA had the most favorable structural parameters for cyclohexenyl ring formation; 4) Four MAC conformers derived from 9<em>c</em>, 11<em>t</em>- and 10<em>t</em>, 12c-CLA, were obtained as final main products that were determined to be <em>cis</em>-cycloadducts; 5) The <em>endo/exo</em> ratios of the <em>cis</em>- cycloadducts derived from 9<em>c</em>, 11<em>t</em>- and 10<em>t</em>, 12<em>c</em>-CLA, were 2.14:1 and 1.99:1, respectively; and 6) The results obtained from the calculation method above were in excellent accordance with those from our experiments.
%K Maleic Anhydride Cycloadducts
%K Improved Preparation
%K Conjugated Linoleic Acid
%K Stereochemical Mechanism
%K Conformers-Ratio Calculation
%K Conformational Isomerization
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=110512