Benchmark Thermochemistry of N-Methylaniline

Abstract

In this work, the standard molar enthalpy of formation in the gaseous state of highly pure N-methylaniline, Δ(f)H(m)°(g, 298.15 K) = 90.9 ± 2.1 kJ·mol⁻¹, has been obtained from the calorimetrically measured energy of combustion converted into the enthalpy of formation, Δ(f)H(m)°(liq, 298.15 K) = 35.9 ± 2.1 kJ·mol⁻¹, and from the molar enthalpy of vaporization, Δ(l)(g)H(m) = 55.0 ± 0.2 kJ·mol⁻¹, derived from vapor pressure measurements by transpiration method. The enthalpy of formation of N-methylaniline calculated using the quantum chemical G4 method was in excellent agreement with the experimental value. The frequencies of normal vibrations were obtained from the experimental and calculated spectra. Thermodynamic properties of N-methylaniline in the ideal gas state were calculated from molecular and spectral data in the temperature range 100-1500 K.

A Database of Formation Enthalpies of Nitrogen Species by Compound Methods (CBS-QB3, CBS-APNO, G3, G4)

“…These lead then to ∆ f H • (298.15 K) of 85.0 ± 0.6 kJ mol −1 for aniline (atomization 90.0±6.8) and 93.8±1.1 kJ mol −1 for N-methylaniline (atomization 95.8±7.8);the latter is in reasonable agreement with a recent combustion calorimetric determination of 90.9 ± 2.1 kJ mol −1 by Emel'yanenko et al77 In the case of aniline there are a number of values near 82 kJ mol −1 and one near 87 kJ mol −1 ; this latter was largely adopted by Pedley et al56 at 87.1 ± 1. kJ mol −1 . It is to be expected that the reaction:C 6 H 5 NH 2 + C 6 H 5 N(CH 3 ) 2 −→ 2 C 6 H 5 NH(CH 3 )would be nearly thermoneutral and the computed reaction enthalpy change of 1.12 ± 0.41 kJ mol −1 confirms this.…”

Thermochemistry of Substituted Benzamides and Substituted Benzoic Acids: Like Tree, Like Fruit?

“…Absolute vapor pressures of chloro‐ and nitrobenzamides were derived by using the gas‐saturation (or transpiration) method according to the ideal gas equation [Eq. ]: …”

Thermodynamic Properties of Trimethylene Urethane (1,3-Oxazinan-2-one)

“…In this work, the thermodynamic functions (Δ f G m 0 , Δ f H m 0 , H T 0 – H 0 0 , G T 0 – H 0 0 , S 0 , and C p 0 ) of trimethylene urethane were estimated by using the rigid rotator– anharmonic oscillator model (Table ). , The necessary set of spectral data for statistical calculations was composed from the experimental and calculated spectra (see Tables S2 and S3). Compilation of the fundamental frequencies used in this study is given in Table S4.…”

“…The equilibrium geometry of trimethylene urethane was optimized with the mPW2PLYP, MP2, and B3LYP methods using the aug-cc-pVTZ and 6-311++G­(3df, 3pd) basis sets of Cartesian functions (6d, 10f) by the Gaussian 09 . The ideal gas thermodynamic properties of trimethylene urethane were calculated as described elsewhere by using a rigid rotator–anharmonic oscillator model. , …”