REACTION OF KETENE IONS WITH AMMONIA

Reactions of ketene ions with NH3, ND3, H2O, and CH4 were investigated in a selected ion flow tube (SIFT). There were no observable products for H2O and CH4 and no ion/neutral complex stabilization in any of the systems investigated. The ammonia system demonstrated two reaction channels, in agreement with previous FTICR data (i) distonic ion CH2NH3.+ formation, with a branching ratio of 0.2 and (ii) proton transfer, with a branching ratio of 0.8. The overall second-order rate constant for NH3 is (2.2 +/- 0.15) x 10(-9) cm3 molecule-1 s-1, in agreement with the gas kinetic ion-dipole collision rate. Isotope scrambling was studied for primary (CH2CO+) and for secondary (CH2NX3.+ and NX4+, X = H or D) proton-transfer reactions with ND3; CH2NH3.+ appears to transfer an X+ ion to ND3 without any scrambling. CH2CO.+ undergoes reaction with partial scrambling and NX4+ seems to react with almost complete scrambling. The results are compared with those of Adams, Smith, and Henchman on the NH4+/ND3 system.