Ethylbromide AKA Bromoethane is a useful alkylating agent and is also a precursor for the synthesis of Nitroethane which makes it handy to have around at time.
Synthesis is based around 53 grams of NaBr that I got at Wal-mart
Molar Weights of reactants:
NaBr Molar mass 102.894 g/mol --- 52 / 102.894 = .5150 or 51.5%
H2SO4 Molar mass 98.08 g/mol * .5150= 50.5112 grams
EtOH Molar mass 46.07 g/mol * .5150 = 23.726
Products
C2H5Br Molar mass 108.97 g/mol * .5150 = 56.1195 Theoretical yeild
H2O Molar mass 18.01528(33) g/mol * .5150 = 9.277
NaHSO4 Molar mass 120.06 g/mol
Reaction:
NaBr + H2SO4 = NaHSO4 + HBr
HBr + EtOH = EtBr + H2O
In the prep excess H2SO4 and EtOH are used to ensure consumption of the NaBr and subsequent conversion to HBr.
23.67ml or in other terms 30 grams of EtOH was placed into a cold water bath and 130 grams of 44% H2SO4(Liquid Lightning MSDS) was added slowly via dropper syringe over a 10 minute period inorder to keep the heat down.
I after
While waiting for the flask to once again reach ambient temperatures 53 grams of Sodium Bromide(Brom Start MSDS) was weighed out and prepared for addition.
After evolution of heat some 15 minutes later or so the flask was placed in an ice bath followed by the slow addition of Sodium Bromide. The mixture quickly took on a red orange color with some Sodium Bromide resting on the bottom.
The flask was allowed to set for 15-20 minutes and the arranged for simple distillation.
The receiver flask was filled about a quarter of the way full of cold spring water and as you can see in the picture above the receiving flask was placed in an ice bath as to not allow the formed Ethyl Bromide to evaporate.
After reaching 58*C at the still head the formed Ethylbromide started to distill over pretty rapidly and the contents of the flask boiled rapidly. The EtBr droped to the bottom of the receiver with a milky white color. This was sustained for about 25 minutes at which point the rapid frothy boiling stopped and the color of the mixture was not noticeably darker. The sound the boiling made now was completely different and unusual. Every time a bubble would form it would do so with a sharp tinny sound to it. It sounded as though it was being boiled in a metal container but I think this may due to the EtBr forming and rapidly vaporizing in the solution resulting in the strange sound because the bubbles where forming in the middle of the flask instead of around the sides like normal. It was at this point that the distillate started to take on a slightly orange tinge to it and the distillate took on a dirtier look to it no doubt carrying some EtOH with it as it made the top H2O layer slightly milky looking until more H2O was added to crash the EtBr out. The remainant of the reaction vessel has now lightened to a pale shade of yellow/orange and after cooling the Sodium hydrosulfate crystallized filling up the vessel.
After about 45 minutes to an hour the distilling was stopped because a bad lightning storm was coming and I am working right next to a large open garage door. The distillate was noticed to be only slightly more dirty the first half of distilling so I just decided to mix both together. This is where one of the notable things happened. When the two distilling flask where added together as soon as the cloudy EtBr hit the air it would release puffs of dense white vapors with the consistency of smoke. I’m pretty sure that its HBr fumes after watching the final product clear up after sitting for an hour.
The yield pre-purification yielded roughly 30ml or 44.1 grams equaling 78.5% yields with more then likely a small amount still in the mother liquid of slightly milky white EtBr with exact weight still to be determined.
Discussion:
This took maybe 3-4 hours total including breaks and allowing the reactions to reach ambient temperatures before moving on so all and all I think this is a nice little synthesis.
I performed this to mainly practice for the bromination of ethylene glycol and the formed Dibromoethane will be added to (aq)NH3 to synthesis EthyleneDiamine which is able to perform the birch reaction at room temperatures and is recoverable after the reduction. Even though most think I want to perform the birch to reduce EDA I really want it as a solvent for NH3 to synthesis Lithium amide.
Since I now have roughly 44 grams of Bromoethane I may as well use it to synthesis some Nitroethane though what do you think.
Synthesis is based around 53 grams of NaBr that I got at Wal-mart
Molar Weights of reactants:
NaBr Molar mass 102.894 g/mol --- 52 / 102.894 = .5150 or 51.5%
H2SO4 Molar mass 98.08 g/mol * .5150= 50.5112 grams
EtOH Molar mass 46.07 g/mol * .5150 = 23.726
Products
C2H5Br Molar mass 108.97 g/mol * .5150 = 56.1195 Theoretical yeild
H2O Molar mass 18.01528(33) g/mol * .5150 = 9.277
NaHSO4 Molar mass 120.06 g/mol
Reaction:
NaBr + H2SO4 = NaHSO4 + HBr
HBr + EtOH = EtBr + H2O
In the prep excess H2SO4 and EtOH are used to ensure consumption of the NaBr and subsequent conversion to HBr.
23.67ml or in other terms 30 grams of EtOH was placed into a cold water bath and 130 grams of 44% H2SO4(Liquid Lightning MSDS) was added slowly via dropper syringe over a 10 minute period inorder to keep the heat down.
I after
While waiting for the flask to once again reach ambient temperatures 53 grams of Sodium Bromide(Brom Start MSDS) was weighed out and prepared for addition.
After evolution of heat some 15 minutes later or so the flask was placed in an ice bath followed by the slow addition of Sodium Bromide. The mixture quickly took on a red orange color with some Sodium Bromide resting on the bottom.
The flask was allowed to set for 15-20 minutes and the arranged for simple distillation.
The receiver flask was filled about a quarter of the way full of cold spring water and as you can see in the picture above the receiving flask was placed in an ice bath as to not allow the formed Ethyl Bromide to evaporate.
After reaching 58*C at the still head the formed Ethylbromide started to distill over pretty rapidly and the contents of the flask boiled rapidly. The EtBr droped to the bottom of the receiver with a milky white color. This was sustained for about 25 minutes at which point the rapid frothy boiling stopped and the color of the mixture was not noticeably darker. The sound the boiling made now was completely different and unusual. Every time a bubble would form it would do so with a sharp tinny sound to it. It sounded as though it was being boiled in a metal container but I think this may due to the EtBr forming and rapidly vaporizing in the solution resulting in the strange sound because the bubbles where forming in the middle of the flask instead of around the sides like normal. It was at this point that the distillate started to take on a slightly orange tinge to it and the distillate took on a dirtier look to it no doubt carrying some EtOH with it as it made the top H2O layer slightly milky looking until more H2O was added to crash the EtBr out. The remainant of the reaction vessel has now lightened to a pale shade of yellow/orange and after cooling the Sodium hydrosulfate crystallized filling up the vessel.
After about 45 minutes to an hour the distilling was stopped because a bad lightning storm was coming and I am working right next to a large open garage door. The distillate was noticed to be only slightly more dirty the first half of distilling so I just decided to mix both together. This is where one of the notable things happened. When the two distilling flask where added together as soon as the cloudy EtBr hit the air it would release puffs of dense white vapors with the consistency of smoke. I’m pretty sure that its HBr fumes after watching the final product clear up after sitting for an hour.
The yield pre-purification yielded roughly 30ml or 44.1 grams equaling 78.5% yields with more then likely a small amount still in the mother liquid of slightly milky white EtBr with exact weight still to be determined.
Discussion:
This took maybe 3-4 hours total including breaks and allowing the reactions to reach ambient temperatures before moving on so all and all I think this is a nice little synthesis.
I performed this to mainly practice for the bromination of ethylene glycol and the formed Dibromoethane will be added to (aq)NH3 to synthesis EthyleneDiamine which is able to perform the birch reaction at room temperatures and is recoverable after the reduction. Even though most think I want to perform the birch to reduce EDA I really want it as a solvent for NH3 to synthesis Lithium amide.
Since I now have roughly 44 grams of Bromoethane I may as well use it to synthesis some Nitroethane though what do you think.