A POTENTIAL SURFACE MAP OF THE H- N2O SYSTEM - THE GAS-PHASE ION CHEMISTRY OF HN2O-/

Dunkin, Fehsenfeld and Ferguson have reported that the gas phase react ion between H- and N2O in a flowing afterglow instrument forms HO- and N-2 with medium efficiency. The potential surface (UMP2-FC/6-311++G( )//RHF/6-311++G(**)) for the H-/N2O system confirms this to be the pr edominant reaction following initial approach of H- towards the centra l nitrogen of N2O to form unstable intermediate [H-(N2O)]. The interme diate then decomposes to HO- and N-2 via a deep channel. The potential surface also shows the direct formation of adducts (O-+N)-O--(H)=N- a nd cis HN=NO-. However, these are formed with excess energy: the forme r converts principally into reactants, while the latter decomposes to HO- and N-2. Ions having the formula 'HN2O-' may be formed in the gas phase by the reactions (i) HNO-+N2O --> HN2O-+NO, and (ii) NH2-+Me(3)C CH(2)ONO --> HN2O-+Me(3)CCH(2)OH. The product anion is stabilized by r emoval of some of its excess energy by the eliminated neutral. Evidenc e is presented which indicates that the product is either cis or trans HN=NO-, or a mixture of both. The characteristic ion molecule reactio n of HN=NO- involves oxidative oxygen transfer to suitable neutral sub strates. For example: HN2O-+CS2 --> HS-+N-2+COS.