Preparation of 2-chlorocinnamic acid
1. Introduction
2-chlorocinnamic acid has important uses in many fields, and its preparation method has attracted much attention. Exploring efficient and feasible preparation paths is of great significance to the development of related industries.

2. Preparation raw materials
1. ** Main raw materials **: Select suitable starting reactants, such as aromatic derivatives with specific structures, which need to have the ability to introduce chlorine atoms in subsequent reactions and construct the activity of cinnamic acid structure.
2. ** Auxiliary reagents **: Prepare the corresponding catalyst, which should be able to effectively promote the reaction, improve the selectivity and rate of the reaction; at the same time prepare a suitable solvent to ensure that the reactants can be fully dissolved and provide a suitable environment for the reaction.

III. Preparation steps
1. ** Chlorination reaction **: The aromatic derivative is placed in the reaction vessel, and an appropriate amount of solvent is added to fully dissolve it. Under specific temperature and stirring conditions, slowly add the chlorine-containing reagent dropwise. This process requires strict control of the reaction temperature and dripping speed to ensure that chlorine atoms are accurately introduced into the target position to generate chlorinated intermediates.
2. ** Carboxylation reaction **: The obtained chlorinated intermediate is transferred to a new reaction system, and carboxylation reagents and corresponding catalysts are added. Under the conditions of heating and pressure, the carboxylation reaction of the intermediate is promoted to form a product with a carboxyl group. This is a key step that directly determines the formation of the parent structure of 2-chloro cinnamic acid.
3. ** Purification step **: After the reaction is completed, the impurities in the reaction system are initially separated by suitable separation methods, such as extraction, distillation, etc. After that, the product is further purified by fine purification methods such as recrystallization and column chromatography, and finally high-purity 2-chloro cinnamic acid is obtained.

IV. Results and discussion
1. ** Product analysis **: The structure and purity of the obtained product were identified by means of melting point determination, infrared spectroscopy, nuclear magnetic resonance and other analytical methods. Contrast the standard map to confirm that the product is 2-chloro cinnamic acid, and determine that its purity meets the relevant requirements.
2. ** Influencing factors **: The effects of reaction temperature, reaction time, proportion of reactants, catalyst dosage and other factors on reaction yield and product purity were discussed. The results showed that appropriate reaction temperature and time, reasonable proportion of reactants and catalyst dosage could effectively improve the reaction yield and product purity.

In conclusion, 2-chlorocinnamic acid can be successfully obtained by the above preparation method, and the method has certain feasibility and reliability, which provides a useful reference for the production of 2-chlorocinnamic acid.