Additions followed by elimination or transfer of protons. In these reactions, the first step is a simple addition but the resulting species is somehow destabilized and undergoes further processing into other products. They are very frequent in inorganic chemistry.
The first step is a simple addition, as described in a previous section, followed by elimination of HF. Among the four boron BX 3 compounds, only the BF3 forms the BF3.H 2 O hydrate, without suffering instantaneous hydrolysis. This is because the strength of the B-X bond varies in the order F> Cl> Br> I, so HX elimination follows the reverse order.
In this example the elimination of a molecule of HF is facilitated by a second water molecule that acts as a bridge in the transfer of a proton. Ab-initio calculations support this fact.
The addition or nucleophilic attack of water, an electron donor, to chlorine, an acceptor produces heterolytic cleavage of the Cl-Cl bond giving the oxocation [OH2 Cl] + , much more acidic than water. This promotes the immediate transfer of protons leading to the final products of the reaction, which are in equilibrium with the reactants.
Thermodynamic data indicate that chlorine is able to oxidize water to oxygen. However this reaction is kinetically slow but is catalyzed by light. That is the reason that aqueous solutions of chlorine should be protected from light to prevent decomposition.
It is an equilibrium reaction
Cl2 + H2O ⇄ Cl- + H+ + HClO Eo= -0.27 V
which is produced by a nucleophilic attack of water on one of the atoms chlorine followed by heterolytic rupture of the Cl-Cl bond and transfer proton to a second molecule of water. In basic medium the reaction is complete.
En presencia de amoniaco el COCl2 genera urea.
COCl2 + 2NH3 ⇄ CO(NH2)2 + 2HCl
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Aqueous solutions of chlorine in the presence of ammonia generate chloramine.
Cl2 + 2 NH3 & # x21C4; Cl- + NH4+ + NH2Cl
In liquid ammonia at -70°C, the above equilibrium has greater constant.
The mechanism shown corresponds to the gas phase and is a nucleophilic attack of NH3 to one of the chlorine atoms followed by heterolitic cleavage of the Cl-Cl bond and proton transfer to a second molecule of NH3.