ION-MOLECULE REACTIONS OF CARBON CLUSTER IONS AND ACRYLONITRILE

Ion/molecule reactions of carbon cluster ions (C(n).+, n = 10-18 and 20) in the gas phase with acrylonitrile (ACN) as the neutral reagent were investigated by Fourier transform ion cyclotron resonance spectrometry (FT-ICR). The carbon cluster ions studied were generated by electron impact ionization of perchlorinated polyaromatic compounds (PPA) and subsequent exhaustive chlorine elimination in the external ion source of the FT-ICR spectrometer. The precursor PPA were prepared by chlorination of the appropriate polyaromatic hydrocarbons using the BMC reagent. The only reaction observed for C(n).+ was the formation of adduct ions stabilized by radiative association (for n = 10-18 and 20) with the exception of C-16.+ which stabilized the adduct ion by loss of a neutral C3. The rate constants for the reaction of C(n).+ with ACN vary from k(bi) = <10(-13) cm3 molecule-1 s-1 (C18.+, C20.+) to k(bi) = 7.1 x 10(-10) cm3 molecule-1 s-1 (C-13.+) and are distinctly larger than with HCN and C2H4 studied before. C-13.+ and C-17.+ exhibit extraordinary reactivity with ACN. For structural information about the product ions C(n+3)H3N.+ formed from C(n).+ and ACN, collision induced dissociation (CID) spectra were obtained by collision of the accelerated product ions of the ion/molecule reactions with argon gas in the FT-ICR cell for two product ions of sufficient large abundances. In addition, the deprotonation of C(n+3)H3N+ (n = 10, 13) product ions by a series of reference bases was studied resulting in a proton affinity of c. 822 and 815 kJ/mol for the conjugate bases C13H2N and C16H2N, respectively.