Ion/molecule reactions of carbon cluster ions and acrylonitrile

Article abstract of DOI:10.1021/ja00071a054

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 C₁₆^?+ 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 × 10^-10 cm³ molecule^-1 s^-1 (C₁₃^?+) and are distinctly larger than with HCN and C₂H₄ studied before. C₁₃^?+ and C₁₇^?+ exhibit extraordinary reactivity with ACN. For structural information about the product ions C_n+3H₃N^?+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+3H₃N⁺ (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.