Various application background and overview of DMAP
Acylation reaction is the most common reaction in chemical reactions. For the acylation reaction of hydroxyl compounds and acid anhydrides, the reaction using pyridine as a catalyst proceeds mildly and reliably. However, when alcohols with greater steric hindrance are acylated, the reaction is difficult and the yield is relatively low. In 1967, Litvinenko and Kirichenko were studying the benzoylation kinetics of m-chloroaniline and found that when 4-dimethylaminopyridine (DMAP) was used as the catalyst instead of pyridine, the reaction rate increased by about 104-105 times. In 1969, Steglich and Hofie also discovered that using 4-dimethylaminopyridine as a catalyst has a strong catalytic effect on the acylation reaction. In recent years, 4-dimethylaminopyridine, as a new high-efficiency acylation catalyst widely used in chemical synthesis, has been extensively studied in the fields of fine chemical industries such as medicines, pesticides, dyes, spices, and functional materials, and relevant experiments have been achieved. As a result, the catalytic effect is remarkable.
Various application structures of DMAP
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In recent years, with the rapid growth of my country’s food industry, the demand for food additives has increased. Research on safe and healthy food additives has become people’s main goal.
1. Sweetener
Sweeteners are additives that give food sweetness. Stevia trifluoromethoxyphenylboronic acid is a natural sweetener. Steviol glycoside is a strong sweetening substance in stevia. The sweetness is about 300 times that of sucrose. However, stevioside has a poor taste. It has a bitter taste at high concentrations, especially under certain conditions, toxic steviol will be produced. In an era when diabetes, obesity, and hyperlipidemia are common diseases, it is urgent to research low-energy, good-tasting, safe and healthy sweeteners. Using the reaction of steviol and amino acids, a new sweetener – steviol active ester was synthesized. Under the catalysis of DMAP, steviol and hydroxyl-containing compounds form active esters, and then react with amino acids to form new sweeteners. This reaction uses DMAP as a catalyst to catalyze the synthesis of steviol active ester. Although the reaction rate is slow and the yield is relatively low, the author conducted comparative experiments without using a catalyst and found that steviol and p-nitrophenol basically do not react. It can be seen that DMAP plays a certain role in catalyzing the synthesis of active steviol esters. 4,1′,6′-Trichloro-4,1′,6′-deoxygalactosucrose is also a sweetener. It is a semi-synthetic product, its sweetness is 600-800 times that of sucrose. Because of its non-toxic, low-calorie, high sweetness, anti-caries, and good stability, it is used as a sweetener for various foods and has a very broad market prospect.
2.Food flavor
Food flavors are a type of food additives that can increase the aroma and flavor of food. O-acetyl lactate, as a type of food flavor compound with a strong ester aroma, is used to prepare various beverages and to make high-quality flavors. Regarding the synthesis of O-acetyl lactate, the traditional synthesis method is to use concentrated sulfuric acid as a catalyst. During the synthesis process, side reactions such as oxidation, dehydration, and polymerization are prone to occur, making the product darker in color, causing odor, and causing the product to The quality is poor, and concentrated sulfuric acid is corrosive to equipment. DMAP was used as the catalyst to synthesize O-acetyl lactylate, and the optimal conditions of the reaction were explored using orthogonal experimental methods. The final research results showed that through gas chromatography analysis, the conversion rate of acetate reached 95%, of which the yield of O-acetyl ethyl lactate was 88% and the yield of O-acetyl butyl lactate was 85%. The best optimized conditions for the synthesis of O-acetyl lactate are DMAP 60mg, n (ethyl lactate or butyl lactate): n (acetic anhydride) = 1:2, temperature 60°C-70°C, time 5h, The final product yield reached more than 80%. After distillation of O-acetyl ethyl lactate, the purity can reach 97%, which meets the requirements for preparing high-quality flavors. Due to the advantages of good catalytic effect, low dosage and high product yield, DMAP has opened up a new way for the development of my country’s flavor synthesis industry.
3. Preservatives
Preservatives are compounds that inhibit the proliferation of microorganisms or kill them. The antibacterial group in preservatives is α,β-unsaturated carbonyl structure. Since there are two symmetrically unsaturated carbonyl structures in the fumaric acid molecule, fumaric acid derivatives also have antibacterial activity. Among them, dimethyl fumarate (DMF) has good antibacterial and antifungal effects. However, because DMF has a pungent smell, is easy to sublimate, and is prone to allergies, its development in the food field has been limited.
4. Cooling agent
Monomethyl succinate is a new cooling agent with refreshing and fresh mint characteristics. Our country has used it as a food additive and has a good market prospect. There are many methods for synthesizing monomenthyl succinate. The new catalyst DMAP is used to directly catalyze the synthesis of monomenthyl succinate from menthol and succinic anhydride. When the reaction conditions are 50°C, 24 hours, n (menthol): n (succinic acid) = 1: 1.5, n (DMAP): n (menthol) = 0. 128: 1, the yield of the product is It is 92.50% and the purity reaches 99.70%. Therefore, this method is used to prepare monomenthyl succinate, the raw materials are simple and easy to obtain, the operation is simple, and the product yield is high. Dimethyl sulfoxide
5. Thickener
Guar gum is a polysaccharide widely used in industry. Its structure mainly contains galactose and mannose. It is mostly used in food, pharmaceutical, cosmetics, health care, petroleum, papermaking, textile printing and dyeing and other industries. As a food additive, guar gum mainly uses guar gum to exhibit high viscosity in water and is used as a food thickener.
6. Functional food additives
Phytosterol ester is a new type of functional food base material that can overcome the low solubility of free phytosterols in water and oil, greatly increase the fat solubility of phytosterols, and can be added more easily When added to oils or oil-containing foods, it has the effect of lowering serum cholesterol levels and is widely used in functional health foods to prevent coronary heart disease.
Preparation of DMAP for various applications
Put bromine dropwise into the pyridine solution, then add dimethylamine hydrochloride, and keep the reaction at 80°C for half an hour. Then add 15% sodium hydroxide aqueous solution. The added sodium hydroxide aqueous solution is mixed with bromine, pyridine, and dimethylamine. The weight ratio of methylamine hydrochloride is 5-6:1.6:1-1.5:2-2.5. Stir and dissolve, let stand for layering, then cool to 0°C for solid-liquid separation. After drying, the finished product 4-dimethylaminopyridine is obtained. The yield of this process can be as high as more than 85% based on pyridine, and the product content can be as high as more than 99.5%.
