The synthesis methods of organic pigments mainly include chemical synthesis and biosynthesis. The following is a detailed explanation of these two methods:
Chemical synthesis
Chemical synthesis is to react suitable raw materials to generate target products through organic chemical reactions. This method usually requires higher temperature and pressure, and has certain environmental pollution. The specific steps are as follows:
1. Diazotization reaction: the reaction of aromatic primary amines and nitrous acid to generate diazonium salts.
2. Coupling reaction: the reaction of aromatic diazonium salts and aromatic amines, phenols or compounds containing active methylene to generate azo compounds.
3. Other reactions: also include electrophilic substitution reactions, ring closure reactions, etc., which are used to generate different types of organic pigments, such as azo pigments, quinacridone pigments, etc.
Biosynthesis
The biosynthesis method is to use organisms such as microorganisms or plants to synthesize organic pigments. This method not only has high selectivity and efficiency, but also can reduce environmental pollution and energy consumption. The specific steps are as follows:
1. Microbial fermentation: fermentation of specific microorganisms in a suitable culture medium to generate the required organic pigments.
2. Plant extraction: Extract organic pigments from specific plants, such as extracting purple pigment from comfrey.
3. Enzyme-catalyzed reaction: Use specific enzymes to catalyze specific chemical reactions to produce organic pigments.
Classification of synthesis methods
According to the type of organic pigment, the synthesis method can be further classified:
1. Azo pigments: Mainly synthesized by diazotization and coupling reactions.
2. Quinacridone pigments: Synthesized by closed-loop reactions, with excellent light resistance, weather resistance, heat resistance, solvent resistance, and migration resistance.
3. Phthalocyanine pigments: Synthesized by metal coordination reactions, with excellent light resistance and heat resistance.
4. Polycyclic or condensed ring compounds: Generated by multi-step organic synthesis reactions, with high durability.
Summary
The synthesis methods of organic pigments are diverse, including chemical synthesis and biosynthesis. Chemical synthesis generates target products through organic chemical reactions, while biosynthesis uses microorganisms or plants to synthesize organic pigments. Different types of organic pigments have different synthesis methods, such as azo pigments, quinacridone pigments, etc.