Introduction
Like chlorine, bromine is extremely dangerous and can easily kill you. In top of this, bromine is a liquid and it’s much more concentrated and therefore more dangerous than chlorine. Bromine is appears as a fuming liquid at room temperature. In organic chemistry, the main use of bromine is for broominating various compounds. Outside of organic chemistry, bromine is mainly used as a substitute for chlorine in pools or spas. And this is very convenient because we’re going to use pool supplies to make the bromine. Make the bromine, these are the three chemicals you will need. Muriatic acid, TCCA, and sodium bromine (NaBr). NaBr here is pre-dissolved in a solution, but you can also use powdered sodium bromide.
TCCA and HCl acid will be used to produce chlorine gas and NaBr is the source of bromine. In short, the chlorine will displace the bromide ion to produce NaCl and Br2. What interesting is the amount of muriatic acid or hydrochloric acid that
is used is three times less than what it’s need if you did it stoichiometrically. It’s possible to use less HCl which means that the possibility of contaminating the final bromine with Hcl is decreased. On the other hand, a stoichiometric amount of TCCA and NaBr is uded.
is used is three times less than what it’s need if you did it stoichiometrically. It’s possible to use less HCl which means that the possibility of contaminating the final bromine with Hcl is decreased. On the other hand, a stoichiometric amount of TCCA and NaBr is uded.
Equipment and glassware:
- Simple distillation setup (three necked round bottom flask, thermometer, condenser, receiving flask and etc);
- Drip funnel (optional);
- Two separatory funnels 250 ml;
- Funnel;
- Heating plate with magnetic stirrer;
- Laboratory scale (0.1-100 g is suitable);
- Retort stand and clamp for securing apparatus;
- Water bath and ice;
- 250 mL x2; 100 x2 Beakers;
- Measuring cylinder 500 mLor 100 mL.
- Pasteur pipet;
- Ampoules;
- Torch;
Reagents:
- NaBr 35% aq solution;
- HCl acid 16% 60 ml;
- TCCA (trichloroisocyanuric acid) 72g;
- H2SO4 conc. 20 ml (optional);
Synthesis
The setup is a relatively basic simple distillation. An additional funnel is attached to the round bottom flask (RBF) but this is optional. In order to limit losses, a long condenser is used and it’s cooled using ice cold water. Every single joint is sealed using concentrated H2SO4 instead of grease, because the acid is more resistant to bromine. The receiving flask is in an ace bath to prevent condensed bromine from escaping. The vacuum adapter leads to an inverted funnel bubbler trap to neutralize any Br2 that escapes. As a precautionary measure against spills, the second half of the distillation apparatus is placed in a container.
1. To the RBF 72g of crushed TCCA is added.
2. To the additional funnel, HCl 16% 60 ml is added.
3. Then, NaBr 35% 400 ml is added to the RBF. Immediately upon addition, some Cl2 comes off of the TCCA and liberate bromine from the sodium salt.
4. HCl acid is then added dropwise with a constant stirring. In case you don’t have the additional funnel, you can also simply pour in the HCl acid and then quickly stopper it. The addition of the HCl is not exothermic to any real degree so adding it quickly isn’t a hazard. In the video, HCl acid is added slowly to keep the concentration of the HCl low to prevent the HCl vapors formation that could contaminate bromine product. When the acid is added, it reacts with TCCA to release chlorine. The Cl2 then reacts with NaBr to form NaCl and Br2. As more and more HCl is added, more Br2 is produced and dark red color of Br2 becomes much more evident.
5. After all acid is added, the solution get very dark red color with some fumes above it.
6. The distillation is carried out in order to separate Br2.
7. As the mixture is heated up and more bromine is liberated the vapors will become darker and darker. When the reaction mixture reach an sufficient temperature point, Br2 is started to condense into liquid and travel down the condenser. As soon as the rate of distillation is decreased, the temperature in the distillation flask is risen and more and more water is started to come over with Br2, the distillation has not to be stopped. There is still a lot of bromine present. The reaction mixture is boiled at 100°C until it completely cleared up. It should reach a point where you don’t see any bromine vapors in the distillation flask.
8. Once this point is reached, the distillation is done and the flask can be removed from heat.
9. There is bromine on the bottom (it’s three times as dense as water) and water layer above it.
10. The Br2 layer is transferred into a separatory funnel to isolate it from water. During these steps, a lot of bromine vapor is released, so it’s important to do in a well ventilated area with a respirator.
12. Once the layers are settled, the lower Br2 layer is drained directly into another separatory funnel.
13. Concentrated H2SO4 20 ml is added to the Br2 in order to dry it. This step must be done very carefully because if water is present, it can be very exothermic and cause Br2 boiling.
14. The next part is the most dangerous part, which is the capping and the shaking to mix the sulfuric acid and Br2. It’s important that the stopper is well greased with sulfuric acid to make sure that no bromine leaks out.
15. The lower bromine layer is then drained into a RBF.
The final dry Br2 yield is 109g (75%). Steps 12-14 are optional in case you need absolutely dry Br2.
2. To the additional funnel, HCl 16% 60 ml is added.
3. Then, NaBr 35% 400 ml is added to the RBF. Immediately upon addition, some Cl2 comes off of the TCCA and liberate bromine from the sodium salt.
4. HCl acid is then added dropwise with a constant stirring. In case you don’t have the additional funnel, you can also simply pour in the HCl acid and then quickly stopper it. The addition of the HCl is not exothermic to any real degree so adding it quickly isn’t a hazard. In the video, HCl acid is added slowly to keep the concentration of the HCl low to prevent the HCl vapors formation that could contaminate bromine product. When the acid is added, it reacts with TCCA to release chlorine. The Cl2 then reacts with NaBr to form NaCl and Br2. As more and more HCl is added, more Br2 is produced and dark red color of Br2 becomes much more evident.
5. After all acid is added, the solution get very dark red color with some fumes above it.
6. The distillation is carried out in order to separate Br2.
7. As the mixture is heated up and more bromine is liberated the vapors will become darker and darker. When the reaction mixture reach an sufficient temperature point, Br2 is started to condense into liquid and travel down the condenser. As soon as the rate of distillation is decreased, the temperature in the distillation flask is risen and more and more water is started to come over with Br2, the distillation has not to be stopped. There is still a lot of bromine present. The reaction mixture is boiled at 100°C until it completely cleared up. It should reach a point where you don’t see any bromine vapors in the distillation flask.
8. Once this point is reached, the distillation is done and the flask can be removed from heat.
9. There is bromine on the bottom (it’s three times as dense as water) and water layer above it.
10. The Br2 layer is transferred into a separatory funnel to isolate it from water. During these steps, a lot of bromine vapor is released, so it’s important to do in a well ventilated area with a respirator.
12. Once the layers are settled, the lower Br2 layer is drained directly into another separatory funnel.
13. Concentrated H2SO4 20 ml is added to the Br2 in order to dry it. This step must be done very carefully because if water is present, it can be very exothermic and cause Br2 boiling.
14. The next part is the most dangerous part, which is the capping and the shaking to mix the sulfuric acid and Br2. It’s important that the stopper is well greased with sulfuric acid to make sure that no bromine leaks out.
15. The lower bromine layer is then drained into a RBF.
The final dry Br2 yield is 109g (75%). Steps 12-14 are optional in case you need absolutely dry Br2.
Storage
The storage of Br2 is extremely difficult and it will leak out of almost any container. The best option for Br2 storage is an ampule. Using a Pasteur pipette, Br2 is carefully transferred to homemade ampules. After Br2 had been transferred to the ampule, it was sealed using a torch. The ampules are stored in a mixture of sand and sodium thiosulfate in a container outside. If an ampule is pop or break indoors, it would be a very big problem.