Gas Phase Reactivity of the CN Radical with Methyl Amines at Low Temperatures (23–297 K): A Combined Experimental and Theoretical Investigation

Abstract

The gas phase reactivity of the CN radical in the presence of dimethylamine (CH 3 ) 2 NH and trimethylamine (CH 3 ) 3 N has been investigated experimentally using a uniform supersonic expansion CRESU reactor coupled to the pulsed laser photolysis/laser-induced fluorescence technique. Rate constants have been obtained in the temperature range 23− 297 K and were found to be independent of temperature for both reactants. A typical rate constant of 5 × 10 −10 cm 3 molecule −1 s −1 is representative of the full set of experiments. Additionally, ab initio calculations at the ROCCSD(T)/6-311++G(3df,2pd)//M062X/6-311++G(d,p) level of theory have been carried out in order to determine the energy profiles along the reaction pathways. The paths corresponding to the hydrogen abstraction with the formation of HCN were found to be barrierless and very exothermic for the two studied reactions. Results are compared to previous works concerning the reactivity of CN with ammonia NH 3 and methylamine CH 3 NH 2 . The energy profile for the reaction with methylamine has been revisited using the level of theory mentioned above. Calculations indicate that hydrogen abstraction is the major reaction pathway as well, in contradiction with a previous investigation claiming that the CN/CH 3 substitution is the dominant exit channel.

A twist on the reaction of the CN radical with methylamine in the interstellar medium: new hints from a state-of-the-art quantum-chemical study

“…Anisotropic hyperfine and nuclear quadrupole tensors are traceless. subsequent work (Sleiman et al 2018a), the quantumchemical investigation was revised, thus pointing out the barrierless formation of CH 2 NH 2 + HCN. However, in (Sleiman et al 2018a), the authors did not take the attack of CN to the NH 2 side into consideration.…”

“…See, subsequent work (Sleiman et al 2018a), the quantumchemical investigation was revised, thus pointing out the barrierless formation of CH 2 NH 2 + HCN. However, in (Sleiman et al 2018a), the authors did not take the attack of CN to the NH 2 side into consideration. In the present study, we have taken a step further by investigating all possible reaction channels, thus demonstrat-ing that two other pathways are feasible.…”

Experimental Studies of Gas-Phase Reactivity in Relation to Complex Organic Molecules in Star-Forming Regions

“…Ion-neutral association reactions have also been investigated in CRESU flows for C + , , N 2 + , O 2 + , CH 3 + , Ar + , NH 4 + , and H 3 O + . The ion-neutral reactions measured to date using CRESU apparatuses are listed in Table . …”

Exploring the Maze of C2N2H5 Radicals and Their Fragments in the Interstellar Medium with the Help of Quantum-Chemical Computations

“…63 Furthermore, our previous work aimed at clarifying some inconsistencies between the experiment and theory. 65,66 There, it was found that abstraction from the CH 3 group proceeds through the formation of an initial prereactive complex that evolves to yield CH 2 NH 2 and HCN as the main products, with a relative energy of −140.2 kJ mol −1 with respect to the reactant asymptote. In addition, a theoretical investigation of the rotational spectrum was carried out for the CH 2 NH 2 radical (as well as for CH 3 NH) to support its laboratory characterization.…”