Standard enthalpies of formation of para-substituted aromatic nitroso oxides

• Published in: Russian chemical bulletin 2023-11, Vol.72 (11), p.2576-2582
• Main Authors: Khursan, S. L., Safiullin, R. L.
• Format: Article
• Language: English
• Subjects: Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Enthalpy; Full Articles; Inorganic Chemistry; Isomers; Nitro compounds; Organic Chemistry; Oxides; Substitutes
• ISSN: 1066-5285; 1573-9171
• DOI: 10.1007/s11172-023-4061-1

Gas-phase standard enthalpies of formation (Δ f H °) of cis - and trans -isomers of fourteen para -substituted aromatic nitroso oxides ArNOO were estimated using the G4 composite method and a comparative analysis of thermochemical characteristics of reference compounds. It was found that the differences between the enthalpies of ArNOO and isomeric nitro compounds ArNO 2 obtained from the G4 calculations are in the range of 270–280 kJ mol −1 and depend only slightly on the electronic properties of the para -substituent. The Δ f H ° values for aromatic nitroso oxides can be estimated more reliably using the homodesmotic reference reaction p -RC 6 H 4 NOO + C 6 H 6 → C 6 H 5 R + C 6 H 5 NOO. A correlation equation Δ f H °( p -RC 6 H 4 NOO) = Δ f H °(C 6 H 5 R) + (250.8±4.3) + + (20.5±1.1) σ p kJ mol −1 ( R = 0.98, σ p is the Hammett constant of the para-substituent R) obtained for the cis -isomers of nitroso oxides ArNOO can be recommended for rapid estimation of the enthalpy of formation of para-substituted aromatic nitroso oxides.