- #1
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Hello everyone,
I watched a MS thesis defence examination on chemistry, and one question was asked to the student, "what is the use of thionyl chloride in the reaction which an amide was transformed to a nitrile?" Unfortunately, there is a "fixed" answer, "to remove water from the reaction medium", which is absolutely wrong in my opinion. The student replied this "babble" and the jury approved this one.
However, I am very curious and restless about the real reason of the reaction, and devised a mechanism, would you please look at the mechanism and say if they are wrong or right?
It would be very informative if I tell you the reaction conditions a bit; dry dimethyl formamide was cooled to 0°C and thionyl chloride was added dropwise, by keeping the temperature below 5°C, under nitrogen atmosphere. When the addition was completed, a greenish yellow color was noticed (note: a literature mentions this reaction as dimethyl formamide+thionyl chloride complex). The amide was then added by small portions, again keeping the temperature below 5°C. The slurry formed after all of the amide was added was stirred for four hours at the same temperature, and the temperature was raised to room temperature and the mixture again stirred for twelve hours at ambient temperature. The mixture was poured on cracked ice and washed with water until pH raises to 5.5-6. There was a strong evolution of sulfur dioxide, so almost all of the reaction steps were advised to be performed under an efficient fume hood.
I refuse that the original reaction involves dehydration, and think that evolutions of sulfur dioxide and hydrogen chloride have fooled them about presence of water in the original medium.
Please give me a hand about this one. Movies, are you around?
I watched a MS thesis defence examination on chemistry, and one question was asked to the student, "what is the use of thionyl chloride in the reaction which an amide was transformed to a nitrile?" Unfortunately, there is a "fixed" answer, "to remove water from the reaction medium", which is absolutely wrong in my opinion. The student replied this "babble" and the jury approved this one.
However, I am very curious and restless about the real reason of the reaction, and devised a mechanism, would you please look at the mechanism and say if they are wrong or right?
It would be very informative if I tell you the reaction conditions a bit; dry dimethyl formamide was cooled to 0°C and thionyl chloride was added dropwise, by keeping the temperature below 5°C, under nitrogen atmosphere. When the addition was completed, a greenish yellow color was noticed (note: a literature mentions this reaction as dimethyl formamide+thionyl chloride complex). The amide was then added by small portions, again keeping the temperature below 5°C. The slurry formed after all of the amide was added was stirred for four hours at the same temperature, and the temperature was raised to room temperature and the mixture again stirred for twelve hours at ambient temperature. The mixture was poured on cracked ice and washed with water until pH raises to 5.5-6. There was a strong evolution of sulfur dioxide, so almost all of the reaction steps were advised to be performed under an efficient fume hood.
I refuse that the original reaction involves dehydration, and think that evolutions of sulfur dioxide and hydrogen chloride have fooled them about presence of water in the original medium.
Please give me a hand about this one. Movies, are you around?