丁烷预聚发蓝工艺
Presently, organic syntheses play an important part in many industries, such as the pharmaceutical field, textile industry and more. From a variety of organic reactions, Friedel Crafts alkylation (FCA) being one of the most important of them. amongst all the varieties of FCA, the reaction of alkylation of benzene with alkyl halides is the most commonly used. The products obtained from benzene alkylation are key to many secondary reactions and also used in many industrial applications.
In this report, we discuss the synthesis of di-p-toulene blue dye (DPTB) from FCA. DPTB is an extensively used primary acid dye for cotton fabrics and consists of an aromatic compound containing four chlorine atoms and an alkyl side chain. The FCA reaction employed for synthesizing DPTB is an alkylation of benzene with para-dichlorobenzene, assisted with aluminum trichloride as a catalyst.
Para-dichlorobenzene (1-chloro-4-chloro benzene) is the perfect feedstock for the FCA reaction, owing to its two vicinal chlorine atoms, and high reactivity. Once the chloride ion is alkylated by a nucleophile, the remaining chlorine atom is easily displaced, leading to a quick reaction kinetics.
Once the feedstock is ready, the reaction mixture is heated to the desired temperature in a round-bottomed flask. The reaction scheme is such that the aromatic ring of para-dichlorobenzene becomes attached to the ring of benzene, displacing one or both of the chlorine atoms. Aluminum trichloride is the catalyst for this reaction, and the most suitable temperature range is between ambient and 90 Celsius.
The ideal molar ratio of the reactants used is 1:1. It is vital to remember that the presence of a catalyst is what helps the very reactive para-dichlorobenzene react with benzene, and without a catalyst, the reaction will not proceed even at elevated temperatures. Upon successful completion of the reaction, the enthalpy of formation is calculated to be 37.6 kcal/mol. The product, p-di-toulene blue dye, is a crystalline solid.
Though the FCA reaction is the primary method employed for the formation of DPTB, there are certain side reactions that take place as well, such as the formation of hydrogen chloride among other by-products. Thus, it is essential to employ proper reaction conditions and work-up procedures to underly the complete removal of all the side/by- products from the reaction mixture. The final product obtained is a deep blue solid, which is extracted from the reaction mixture and air dried for 24hrs.
DPTB is extensively used in the textile industry for dyeing cotton fabrics, as it is a professional easy-wash dye. It is also known for its excellent resistance to fading and stretching of fabrics. Due to the immense demand and consistent supply of p-di-toulene blue dye in the market, it has managed to remain one of the most profitable commercial activities.
Overall, synthesizing DPTB through FCA is fast, efficient, economical, and practical. The product has a unique application in the textile industry. The catalytic activity of aluminum chloride allows for quick formation of a desired product, which is cost-effective and environment-friendly.
