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The gas-phase pyrolysis of cyclopropylamine: Quantum chemical characterisation of the intermediates involved
Article
Date:
2020Publishing House and Editing Place:
TAYLOR & FRANCIS LTDMagazine:
MOLECULAR PHYSICS, vol. 119 (pp. 1-16) TAYLOR & FRANCIS LTDSummary
A computational study on the molecular structure, harmonic vibrational frequencies and thermochemical parameters of the postulated intermediates and final products involved in the gas-phase pyrolysis of (c-C3H5)NH2 (CPA) has been carried out by ab-initio and DFT methods. Internal rotor potentials were determined employing CAS-MP2 calculations for the singlet ?H2CH2?HNH2 biradical and DFT for singlet CH3CH2C?NH2, cis- and trans-CH3CH=CHNH2, E- and Z-CH3CH2CH=NH, (c-C3H5)NHCH(NH2)CH2CH3, E- and Z-(c-C3H5)N=CHCH2CH3. The enthalpies of formation at 0 and 298 K for these species were derived from isodesmic reactions using the B3LYP and M06-2X functionals coupled to the 6-311++G(3df,3pd) basis set and ab-initio G3(MP2) and G3(MP2)//B3LYP/6-311++G(3df,3pd) composite models. At the last level, enthalpies of formation at 298 K of 69.94 and 40.37 kcal mol?1 were estimated for the first time for ?H2CH2?HNH2 and CH3CH2C?NH2, and values of 7.28, 8.12, 5.37 and 6.08 kcal mol?1 were derived for cis-CH3CH=CHNH2, trans-CH3CH=CHNH2, E-CH3CH2CH=NH and Z-CH3CH2CH=NH, respectively. Accordingly, the pyrolysis of CPA to give ?H2CH2?HNH2 and CH3CH2C?NH2 is predicted to be endothermic by 51.58 and 22.01 kcal mol?1, whereas all other reaction steps are exothermic. For the overall reaction, 2 CPA ? (c-C3H5)N=CHCH2CH3 + NH3, a standard change in enthalpy of about ?20 kcal mol?1 was obtained.Key Words
SINGLET ?H2CH2?HNH2SINGLET CH3CH2?NH2QUANTUM-CHEMICAL CALCULATIONSCYCLOPROPYLAMINE PYROLYSISTHERMOCHEMISTRY