Some day in 1995. The lab in Jorhat, Assam. A PhD student wanted an ambered glass bottle for storing of his solvent. He found one with something inside it. He did not look at what was inside but straight away went to the washbasin and tried to clean the bottle. When he poured water inside the bottle, a big explosion occurred with some fire. Everything happened instantly but no one was hurt as the lab attendant extinguished the fire with a fire extinguisher. Everyone just shocked what has happened and found that there was some sodium wire inside the bottle and vapour of Tetrahydrofuran solvent. We all thankful to God that nothing big destruction occurred.
The next morning we all came at 8.30 AM but the student did not appear. When he did not come till 12 pm, the lab attended went to his place upon request of the Head scientist. The student was living alone in a private rental dormitory in front of the research institute. When lab attendant arrived his room he asked the landlord about the student but they did not notice anything about him. Then they were alert too and went to his room together with the lab attendant when they knew that he did not go to the lab that day. The door was hooked from inside. They called him but no answer. Finally, they broke the door and saw the dead body of the student on the bed. Post mortem report revealed the cause of heart failure while sleeping. It was thought that he might get a big shock from the incident in the previous day. The rest of the day became very sad for all the people of the institute.
Chemistry: We use sodium in the form of wire to make tetrahydrofuran solvent dry. After the use of all the dry solvents, we usually destroy the remaining sodium metal by using methanol or ethanol which reacts with sodium to make sodium alkoxide. We have to pour slowly methanol in the sodium wire and as the reaction is exothermic, a condenser is used to reflux the methanol. Normally for drying THF.we should use a transparent bottle not ambered glass so that it is easy to see the blue colour of Na-benzophenone ketyl radical ion. We use a little bit of benzophenone in the THF and reflux the solvent with sodium metal until it appears blue. The blue color indicates the solvent is absolutely dry. Then we keep it like that and when needed we distill some amount from it for reactions.
The mechanism: Sodium metal reacts with the residual water in the THF solvent and form sodium hydroxide in refluxing condition. When all water reacted with sodium and the solvent gets dry, the sodium metal and the benzophenone form the Sodium benzophenone ketyl radical which is deep blue color species. The reaction scheme is showing the structure of the species below.
The Lesson:
1. We must avoid ambered glass bottles for keeping sodium wire.
2. We must never leave sodium metal dry and destroy immediately after use. Commercially it kept under kerosene.
The next morning we all came at 8.30 AM but the student did not appear. When he did not come till 12 pm, the lab attended went to his place upon request of the Head scientist. The student was living alone in a private rental dormitory in front of the research institute. When lab attendant arrived his room he asked the landlord about the student but they did not notice anything about him. Then they were alert too and went to his room together with the lab attendant when they knew that he did not go to the lab that day. The door was hooked from inside. They called him but no answer. Finally, they broke the door and saw the dead body of the student on the bed. Post mortem report revealed the cause of heart failure while sleeping. It was thought that he might get a big shock from the incident in the previous day. The rest of the day became very sad for all the people of the institute.
Chemistry: We use sodium in the form of wire to make tetrahydrofuran solvent dry. After the use of all the dry solvents, we usually destroy the remaining sodium metal by using methanol or ethanol which reacts with sodium to make sodium alkoxide. We have to pour slowly methanol in the sodium wire and as the reaction is exothermic, a condenser is used to reflux the methanol. Normally for drying THF.we should use a transparent bottle not ambered glass so that it is easy to see the blue colour of Na-benzophenone ketyl radical ion. We use a little bit of benzophenone in the THF and reflux the solvent with sodium metal until it appears blue. The blue color indicates the solvent is absolutely dry. Then we keep it like that and when needed we distill some amount from it for reactions.
The mechanism: Sodium metal reacts with the residual water in the THF solvent and form sodium hydroxide in refluxing condition. When all water reacted with sodium and the solvent gets dry, the sodium metal and the benzophenone form the Sodium benzophenone ketyl radical which is deep blue color species. The reaction scheme is showing the structure of the species below.
The Lesson:
1. We must avoid ambered glass bottles for keeping sodium wire.
2. We must never leave sodium metal dry and destroy immediately after use. Commercially it kept under kerosene.
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