| Chloro-carboxylic acid has an irreplaceable role in the industry.The chlorinated carboxylic acid molecule contains two active functional groups:carboxyl and chlorine atoms,wherein the carboxyl group can undergo chemical reactions such as esterification,amidation,and amination,and generate organic substances such as salts,esters,amides,acid chlorides,and the like.Chlorine atoms can be replaced by bromine,iodine,amino,cyano,hydroxyl and other functional groups to produce the corresponding organic compounds.Therefore,chlorinated carboxylic acids are widely used in many fields as organic intermediates and have good application prospects.Chlorocarboxylic acids are widely used.However,many by-product sinevitably were produced in the chlorinated carboxylic acids synthesis process.The appearance of these by-products not only consumes large quantities of raw materials,but also,as the main product and the corresponding vice The physical and chemical properties of products close,resulting in their separation and purification is not easy to operate,the accumulation of a large number of by-products,not only will process equipment serious corrosion,but also cause environmental pollution.In view of the above problems,it is very necessary to study the reaction mechanism of chlorocarboxylic acids.Starting from the reaction mechanism,we explore ways to inhibit the production of by-products of chlorocarboxylic acids and increase the yield of chlorinated carboxylic acid main products,which is very favorable to promote the development of chlorinated carboxylic acid production process.Therefore,on the basis of inquiring a large number of documents and drawing on the previous studies,I conducted the following three aspects of this paper using density functional theory:First,the paper uses the DMol~3 module in MS software to explore the synthesis mechanism of 2-chloropropionic acid.The study found that the activation energy of the 2-chloropropionic acid synthesized via the ion mechanism is lower than that of the free radical mechanism.Therefore,the synthesis of 2-chloropropionic acid mainly through the ionic mechanism.In the entire reaction process of the synthesis of 2-chloropropionic acid,first,propionic anhydride initiates the reaction to form a true catalyst propionyl chloride,and then the ion reaction is started to obtain the final product 2-chloropropionic acid.propionyl chloride is synthesized.The step which 1-chloro-1-hydroxy-1-propene is synthesized via propionyl chloride is the rate-controlling step of the entire ionic chlorination mechanism in the synthesis process.In addition,the experimental studies have also found that the synthesis route of3-chloropropionic acid is mainly via the free radical chlorination mechanism,and then,2,3-dichloropropionic acid can be further generated by free radical chlorination;2,2-dichloropropionic acid mechanistic research shows that it is more difficult to synthesize the ionic mechanism by the free radical mechanism,so that 2,2-dichloropropionic acid is mainly obtained via the ionic mechanism pathway.Meanwhile,2,2-dichloropropionic acid and 2-chloropropionic acid are a series of reactions,2,2-dichloropropionic acid can be obtained by continuous ionic chlorination of 2-chloropropionic acid,which is an important intermediate for the production of 2,2-dichloropropionic acid.Second,the article also studied the synthesis mechanism of 2-chlorobutyric acid,the data show that the synthesis of 2-chlorobutyric acid mainly through the ion mechanism,the first reaction of butyric anhydride initiation,which form the chlorobutyryl chloride catalyst,and then the ion synthesis reaction,in which,butyryl acid catalyzed enolization to synthesize 1-chloro-1-hydroxy-1-butene is the controlling step of the whole ionic reaction.In addition,the synthesis of 3-chlorobutyric acid and 4-chlorobutyric acid mainly through the ion mechanism,at the same time,1-chloro-1-hydroxyl-1-butene synthesis process is also the whole ion reaction rate control step,in which 4-chlorobutyric acid is the main chlorine by-product.In addition,studying the reaction mechanism of dichloro byproducts,it was found that the activation energy of2,4-dichlorobutyric acid synthesized by the ion mechanism is lower than that of chlorine radicals.Therefore,2,4-dichlorobutyric acid is mainly passed via the ion mechanism pathway.In addition,the analysis of 2,2-dichlorobutanoic acid and 2,3-dichlorobutyric acid found that their reaction through ionic mechanism requires higher activation energy than the reaction mechanism of chlorine radicals,and the ionic reaction is more difficult,so 2-dichlorobutyric acid and2,3-dichlorobutyric acid are mainly obtained through the mechanism of chlorine free radical reaction.At the same time,the research has been found that2,4-dichlorobutyric acid,2,2-dichlorobutyric acid and 2,3 are obtained by successive chlorination of 2-chlorobutyric acid by continuous chlorination and free radical continuous chlorination.2-butyryl chloride is an intermediate for synthesizing them.Third,in this part,the hydrogenation reduction of 2-Chloropropionic acid and chloroacetic acid by-products is studied,the experimental data show that at the reaction temperature of 120?,the catalyst amount of 0.75g,the chloroacetic acid hydrogenation reduction best When the reaction temperature is 140?and the amount of catalyst is 0.5 g,the?-chloropropionic acid by-product is obtained by hydrogenation to obtain the best effect.In addition,the reaction mechanism of this section was checked to find that chloroacetic acid by-products hydrogenated mainly to produce chloroacetic acid,and the energy of producing acetic acid directly was relatively high and was not easy to occur.At the same time,the hydrogenated reduction of 2-chlorpropionic acid can produce 2-chlorpropionic acid and 3-chlorpropionic acid,in which 2-chlorpropionic acid is more easily synthesized,while the activation energy of the by-product 2,3-dichloro propionic acid,2-chlorpropionic acid and 3-chlorpropionic acid directly hydrogenated to propionic acid is relatively large and is not easy to carry out. |
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