2,3,5-Trimethylpyrazine
2,3,5-Trimethylpyrazine (chemical formula C7H10N2) is one of the most broadly used edible synthesis fragrances. It comes from baked food, fried barley, potatoes, and peanuts. 2,3,5-Trimethylpyrazine is used for the flavor in cocoa, coffee, chocolate, potato, cereal, and fried nuts. Physical properties The specific gravity depends on the quality and the producer and ranges from 0.967 to 0.987. Synthesis 2,3,5-Trimethylpyrazine can be synthesized from 2,3-butanedione and 1,2-diaminopropane. First, 1,2-diaminopropane is synthesized by amination of isopropanolamine in the presence of ammonia and a hydrogenation catalyst: Raney Ni. The effect of the amount of Raney Ni catalyst, the molar ratio of materials, reactions are as follows: the molar ratio of isopropanolamine to ammonia is 1:3.5,the reaction temperature is 160 °C, the reaction is 5 hours, the molar ratio of hydrogen to isopropanolamine is 1:5. Then the reaction consists of synthesis of 2,3,5-trimethyl-5,6-dihydropyrazine and 2,3,5-trimethylpyrazine. The optimum conditions of 2,3,5-trimethyl-5,6-dihydropropyrazine synthesis are established:2,3-butanedione which is mixed with anhydrous ethyl alcohol (the mass ratio of anhydrous ethyl alcohol to 2,3-butanedione was 5:1) is dropped to the mixture of anhydrous ethyl alcohol and 1,2-diaminopropane (the mass ratio of anhydrous ethyl alcohol to 1,2-diaminopropane was 6:1) at the even pace for four hours, the molar ratio of