Talk:Carbonyl bromide

Application[edit]

Can carbonyl bromide be used as a substitute for phosgene in chemical synthesis, due to its lower volatility? Or does the contamination by elemental bromine (which is produced by slow decomposition) interfere with these applications? The storage of carbonyl bromide should not be a great problem, despite its instability, storage could be fulfilled by keeping it cool and dark and in a gas proof container in order to keep the chemical equilibrium of its decomposition on the left side. --79.243.250.55 (talk) 11:41, 3 August 2013 (UTC)[reply]

Even if the decomposition is an equillibrium reaction (see below), the pressure of the carbon monoxide may blow up most chemical containers if they have been closed gas-proof, forcing to let the container opened. That causes difficulty with longer storage because under this conditions the whole sample will slowly decompose. So carbonyl bromide possibly isn't a useful substitute for phosgene in chemical synthesis... --79.243.254.210 (talk) 20:15, 15 September 2013 (UTC)[reply]

"endergonic" compound?[edit]

The given value of the enthalpy of formation for carbonyl bromide is (seen as absolute values) lower than that of carbon monoxide. Is this possible? It would imply that the reaction CO + Br₂ -> COBr₂ is endothermic, and furthermore, that carbonyl bromide is thermodynamically unstable, because the reaction's entropy of the reaction above is clearly negative (two particles convert to one), unable to make a ΔG < 0 possible at any temperature if ΔH > 0. Thus, carbonyl bromide had to be very unstable, according to the given values... --79.243.242.143 (talk) 21:15, 6 September 2013 (UTC)[reply]

And it is, as expected: "Even at low temperatures, carbonyl bromide decomposes to carbon monoxide and elemental bromine." (from the article) Double sharp (talk) 04:54, 8 September 2013 (UTC)[reply]

But, if carbonyl bromide is an unstable species, how can it be formed as an oxidation product of brominated hydrocarbons upon contact with fire (also form the article)? The high temperatures would lead to very quick decomposition of the compound if it is not thermodynamically stable at all, so it could at most be a short-lived intermediate, comparable e.g. to peroxides... --130.83.100.213 (talk) 14:00, 9 September 2013 (UTC)[reply]

Some sources on the internet (but I'm afraid no serious ones) cite that K_c for the reaction COBr₂ <-> CO + Br₂ (that means the expression c(CO)*c(Br₂)/c(COBr₂) ) is 0.19 at 73°C. I can neither say where this is taken from, nor if it's true, but if it is, the formation of carbonyl bromide must be an exothermic reaction - otherwise K had to be >> 1 for every temperature.

Of course, this would not automatically imply that carbonyl bromide must be stable. If left in an open container, it can still decompose and the carbon monoxide - instead of reacting back - diffuses away, so the reaction is pulled to the right side by the steady loss of CO. --79.243.237.11 (talk) 17:09, 10 September 2013 (UTC)[reply]

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