Dichlorine heptoxide is the chemical compound with the formula . This chlorine oxide is the anhydride of perchloric acid. It is produced by the careful distillation of perchloric acid in the presence of the dehydrating agent phosphorus pentoxide: It slowly hydrolyzes back to perchloric acid.
Structure
is an endergonic molecule, meaning it is intrinsically unstable, decomposing to its constituent elements with release of energy:
: (ΔH° = −132 kcal/mol)
Dichlorine heptoxide is a covalent compound consisting of two groups linked by an oxygen atom. It has an overall bent molecular geometry (C<sub>2</sub> symmetry), with a Cl−O−Cl angle of 118.6°. The chlorine–oxygen bond lengths are 1.709 Å in the central region and 1.405 Å within each cluster.
:2
:2
It also reacts with alkenes to give alkyl perchlorates. For example, it reacts with propene in carbon tetrachloride solution to yield isopropyl perchlorate and 1-chloro-2-propyl perchlorate.
Dichlorine heptoxide reacts with alcohols to form alkyl perchlorates.
:
Dichlorine heptoxide is a strongly acidic oxide, and in solution it forms an equilibrium with perchloric acid.
Safety
Although it is the most stable chlorine oxide, is a strong oxidizer as well as an explosive that can be set off with flame or mechanical shock, or by contact with iodine. Nevertheless, it is less strongly oxidising than the other chlorine oxides, and does not attack sulfur, phosphorus, or paper when cold.