NOTES 1. The aqueous solution of sodium nitrite should not be added too fast, so
ID: 691821 • Letter: N
Question
NOTES 1. The aqueous solution of sodium nitrite should not be added too fast, so as to avoid the waste of sodium nitrite. 2, Zinc powder should not be added at one-time, otherwise the reaction is too intense, and the reduction is incomplete After adding chlorobenzoyl chloride, the initial reaction temperature should not exceed 30 C to avoid decomposition of chloride. 4, There are two crystal forms of indomethacin, one is flocculent with low melting point and solubility, the other is granular with high melting point and low solubility. In the lization process, if flocculent was get, it should be dissolved again and re-crystallized, if a I forms was get, trying to control the heating temperature and time, so as al to dissolve the flocculent and leaving a granular as crystal seed. QUESTIONS 1, Why inserted the feeding tube below the reaction solution while adding sodium nitrite? 2, In the preparation of N- chloro-benzoyl- methoxy phenylhydrazine, what is the purpose of adjust the pH to 10-11 with alkali and reacted within 60-65 for 15 min? REFERENCES Zhuo Chao, Shen Yongjia, Higher Education Press, "the pharmaceutical industry professional experiment" P116-118,2007Explanation / Answer
Q's
1. A tube is inserted to feed sodium nitrite below the reaction solution instead of directly adding the sodium nitrite in one go. This is to avoid formation of waste of sodium nitrite due to incomplete reaction by fast addition of salt.
2. In the preparation of N-chloro-benzoyl-methoxy phenylhydrazine, the pH is adjusted to approximately about 10-11 and the solution was heated at 6-65 oC for about 15 min. This is done to make the hydrazine which is present in acidic salt form, neutralize and free hydrazine is generated for the reaction to occur.
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