Production of Cyanogen Bromide

by Eleusis

Hey, in case you are still with us after trying out all my other fun-at-home projects, perhaps you feel ready to embrace *real* danger? How about making your own Cyanogen Bromide, which is about as fun-loving as a compound can get! You have immense toxicity in combination with that all-around party favorite - instability! Kids, *don't* try this at home.


This stuff is deadly toxic and unstable. It should only be prepared immediately before use (no storage whatsoever). Perform this reaction outside on a windy day, or with a good fume hood (no, I don't mean the fan over the stove). Cyanogen Bromide has been known to decompose explosively on standing... you have been warned.

The general reaction, in which much substitution of compounds may take place, is below:

NaCN + Br2 BrCN + NaBr

For the first half of the reaction, assemble a ground glass joint setup consisting of a 500mL round bottom flask, a claisen adapter, an addition funnel in the sidearm of the adapter, and a thermometer down the center. Place this in an ice/water bath on a magnetic stirrer.

Add 50g of elemental Bromine to the flask, followed by 5mL of water and a stirrer magnet. Start stirrer, and reassemble the thermometer adapter such that the thermometer will read the liquid temperature. Dissolve 17g of Sodium Cyanide in 120mL of warm water and add this gradually to the flask through the addition funnel, taking care that the reaction temperature does not exceed 25-30C. The time it takes to add the NaCN solution is quite variable, but the total reaction time should be around 2 hours.

At the the end of this time, remove the claisen adapter and replace with a 3-way distilling adapter to which a 500mL round bottom flask is connected *directly* to the outlet tube. Insert the thermometer in conventional manner (to read the vapor temperature) and distill off the BrCN using a water or steam bath. It should boil at 60-62C.

Clean off all of the glassware, then add 10g of anhydrous Calcium Chloride to the receiver flask and reassemble the same setup as previously. Redistill the crude BrCN from the CaCl2 as before. Once all has been collected over the range of 60-62C, melt the solid in the receiver by heating to 51C (note the closeness between melting and boiling!) and pour into a pre-weighed glass bottle. The yield should be 23-28g, or approximately 73-85% of the theoretical. If it will not be used immediately, it may be stored in the freezer, but should be used as soon as possible.


  • Organic Syntheses, Collective Volume 2, (1943), pp150-1
  • Berische, volume 29, (1896), pg 1823

- - The Cyanogen Bromide Doc - 09/19/95 -