Solvent in the dye synthesis process

The components and proportions of the solvents used in the synthesis of different products vary; detailing the problem helps to resolve it more effectively.

1. Acid dyes: Acid dyes often contain one or several sulfonic acid groups, making them highly polar compounds; when using untreated paper, aqueous solutions of polar acid developing agents are commonly employed. ①n-Butanol∶Acetic acid∶Water = 2 ∶1 ∶5 (1 ∶1 ∶1) ② Acetic acid∶Concentrated hydrochloric acid∶Water = 200 ∶1 ∶30 ③ 2% hydrochloric acid ④ 25% ethanol∶25% ammonia water = 1 ∶1 ⑤ n-Butanol∶Pyridine∶Water = 3 ∶1 ∶1 2. Direct dyes: Direct dyes have a high affinity for paper and produce long staining trails; they are generally used in conjunction with paper treatment or appropriate developing agents to achieve good results. ①The paper was pretreated with 7.5 mL of formamide and 142.5 mL of ethanol, or with hexadecanol in 2% ethanol. Developing agents: Ethyl acetate∶Pyridine∶Water = 3 ∶4 ∶3; n-Pentanol∶Pyridine∶25% ammonia water = 1 ∶1.3 ∶1; ② n-Butanol∶Pyridine∶25% ammonia water = 2 ∶1 ∶2; ③ n-Butanol∶Ethanol∶Water = 3 ∶1 ∶1; ④ n-Butanol∶Concentrated ammonia water = 2 ∶1; ⑤ n-Butanol∶Pyridine∶Water = 5 ∶3 ∶5. 3. Reactive dyes: Since the molecular structure of reactive dyes contains highly polar, water-soluble groups, developing agents with high polarity should be chosen. On the other hand, since the dye has structural groups that can react with alkalis, it is advisable to avoid using solvents with high alkalinity. ①n-Butanol∶Acetic acid∶Water = 2 ∶1 ∶5 ； 4 ∶1 ∶5 ； 16 ∶4 ∶1 ； 16 ∶14 ∶9 ② Butanol∶DMF ∶Water∶Glacial acetic acid = 10 ∶3 ∶11 ∶2 ③ n-Propanol∶Acetic acid∶Water = 5 ∶2 ∶3 ④ n-Butanol∶Water∶DMF = 11 ∶11 ∶3 ⑤ n-Butanol∶Pyridine∶Water∶Ammonia water = 4 ∶5 ∶4 ∶1 4. Disperse dyes: Disperse dyes are insoluble in water, so reverse-phase chromatography is a suitable method; in this approach, paper is soaked in α-bromonaphthalene (10% α-bromonaphthalene in methanol or acetone), and an aqueous polar solvent is used as the eluent. The resulting spots are concentrated and circular in shape. ①α-bromonaphthalene/60~80% ethanol ； ②α-bromonaphthalene/60–80% acetic acid ③ α-bromonaphthalene/pyridine∶water = 1 ∶3 (azo type) ； 1 ∶5 (anthraquinone type) ④ Formic acid∶Acetic acid∶Water = 9 ∶9 ∶2 ⑤ Formic acid∶Water∶Acetic acid = 14 ∶20 ∶1 (8 ∶1 ∶1) ⑥ Butanol∶Acetic acid∶Water = 4 ∶1 ∶5 (upper layer) ⑦ Cyclohexane∶Formic acid∶Water = 4 ∶3 ∶1 (upper layer) ⑧ Benzene∶Cyclohexane∶Formic acid = 1 ∶1 ∶1 ⑨ Petroleum ether (90%)∶Ethyl acetate = 2 ∶1 ⑩ Butanol∶HCl = 4 ∶1 5. Cationic dyes are suitable for chromatographic separation in alkaline media. ①2.5% lauryl alcohol solution soaked paper: Methanol∶ammonia water = 1∶1; Ethanol∶ammonia water = 1∶1; Ethanol∶1N hydrochloric acid = 1∶1. ② Methanol∶acetic acid∶water = 2∶1∶1 (4∶2∶1). ③ Methanol∶ammonia water∶water = 63∶40∶77. ④ Pyridine∶ammonia water∶water (various ratios). 6. Metal complex dyes: Metal complexes are soluble in polar solvents such as water, acids, alcohols, and pyridine, but not in organic solvents. ①12% pyridine ② n-Butanol∶pyridine∶water = 5 ∶3 ∶5 (3 ∶1 ∶1) ③ Ethyl acetate∶butyl acetate∶acetic acid∶water = 1 ∶7 ∶2 ∶4 ④ 60% acetic acid (for separating 1∶1 metal-complex dyes) ⑤ 60% acetic acid (using acetylated paper to separate 2∶1 metal-complex dyes) ⑥ n-Butanol∶acetic acid∶water = 2 ∶1 ∶5 ⑦ 2% HCl 7. Soluble reducing dyes ① 25% ammonia water∶methanol∶water = 1 ∶2 ∶3 ② Pyridine∶isopentanol∶25% ammonia water = 1.3 ∶1 ∶1 ③ Methanol∶acetic acid∶water = 4 ∶1 ∶1 8. Soluble sulfiding dyes ① Pyridine∶n-butanol∶water = 2 ∶1 ∶1 (3 ∶1 ∶1) ② Pyridine∶ethyl acetate = 1 ∶1 (2 ∶1) ③ Pyridine∶benzene∶ethyl acetate = 2 ∶2 ∶1 9. Reducing dyes In paper chromatography for reducing dyes, the dyes are generally converted into leuco forms before separation is carried out. ①Potassium persulfate : Water : 4N NaOH : Pyridine = 10 g : 80 : 10 : 10 (under nitrogen atmosphere). ② A simple chromatographic method for reducing dyes, using a freshly prepared developing agent. Distilled water: 32 mL; Turkish red oil (1% solution): 48 mL; 35% NaOH: 4 mL; Safety powder (industrial grade): 4 g; Pyridine: 16 mL

The summary upstairs is good; in fact, it needs to be applied flexibly during the work process. Choosing based on polarity is very important, and a good solvent helps in making decisions regarding synthesis!