Growth of polyphenyls via ion–molecule reactions: An experimental and theoretical mechanistic study

Abstract

The reactivity of biphenylium cations C12H9(+) with benzene C6H6 is investigated in a joint experimental and theoretical approach. Experiments are performed by using a triple quadruple mass spectrometer equipped with an atmospheric pressure chemical ion source to generate C12H9(+) via dissociative ionization of various isomers of the neutral precursor hydroxybiphenyl (C12H10O). C-C coupling reactions leading to hydrocarbon growth are observed. The most abundant ionic products are C18H15(+), C18H13(+), C17H12(+), and C8H7(+). The dependence of product ion yields on the kinetic energy of reagent ions, as well as further experiments performed using partial isotopic labelling of reagents, support the idea that the reaction proceeds via a long lived association product, presumably the covalently bound protonated terphenyl C18H15(+). Its formation is found to be exothermic and barrierless and, therefore, might occur under the low pressure and temperature conditions typical of planetary atmospheres and the interstellar medium. Theoretical calculations have focussed on the channel leading to C8H7(+) plus C10H8, identifying, as the most probable fragments, the phenylethen-1-ylium cation and naphthalene, thus suggesting that the pathway leading to them might be of particular interest for the synthesis of polycyclic aromatic hydrocarbons. Both experiments and theory agree in finding this channel exoergic but hampered by small barriers of 2.7 and 3.7 kcal mol(-1) on the singlet potential energy surface.

Polar molecules engaged in pendular states captured by molecular-beam scattering experiments

“…We anticipate that the treatment, developed to rationalize the experimental findings, allows us to verify that the effective orienting electrostatic field is at least of the same order of magnitude than those exploited in the brute force technique [8] and that the generated pendular motions survive for the few picoseconds, which are typical of the collisional times. Therefore, the results of the present study can help to rationalize within a unifying picture recent experimental findings arising from the control exerted by long-range anisotropic forces on the microscopic mechanism of openshell atom-molecule [24,29], free radical-molecule [30,31], and ion-molecule chemical reactions [32][33][34][35].…”

“…[66]), in proton transfer and hydrogen-bond switching phenomena [63,[67][68][69][70][71][72]. Moreover, being of general validity, the results of this investigation can be useful to shed light on the stereodynamics of several bimolecular chemical reactions involving anisotropic molecules and open-shell atoms [24,29], free radicals [30,31], and ionic species [32][33][34][35].…”

Is the Reaction of C3N– with C2H2 a Possible Process for Chain Elongation in Titan’s Ionosphere?

“…In Trento the reactivity of C 3 N – anions with acetylene was investigated by using a triple quadrupole mass spectrometer TQ-MS (model API3000TM LC/MS/MS, AB Sciex, USA) equipped with an atmospheric pressure chemical ionization-heated nebulizer source (APCI) that has been previously used to study reactivity between cations and various neutrals. , Deuterated acetylene C 2 D 2 used for some of the experiments was synthesized from CaC 2 and D 2 O and stored in a glass reservoir. C 3 N – anions were generated using acrylonitrile (CH 2 CHCN) as neutral precursor, via an APCI source by in-source collision-induced dissociation with N 2 used as declustering gas.…”

The reactivity of cyclopropyl cyanide in titan's atmosphere: a possible pre-biotic mechanism

“…Experiments have been carried out using a Triple Quadrupole Mass Spectrometer (model API3000TM LC/MS/MS, ABSciex, USA) at the University of Trento, equipped with atmospheric pressure ion sources such as APCI (Atmospheric Pressure Chemical Ionisation) and ESI (ElectroSpray ionization), and previously used to study reactivity of cations and anions with stable neutrals 31,32,33 . A schematic diagram of the set-up is given in Figure 1.…”