Heats of formation of C1?C4 alkyl nitrites (RONO) and their RO-NO bond dissociation energies

Abstract

The heats of formation of Cs and C, alkyl nitrites (RONO) have been determined via their heats of combustion by bomb calorimetry, thereby providing a complete set of values of AH'/ for CI-C, alkyl nitrites. The experimental values are in excellent agreement with values derived from group additivity rules. For branched compounds these calculations involve corrections for gauche interactions. In these cases, the gauche interactions are reflected in the activation energies El determined by recent kinetic studies, required for breaking the RO-NO bond.The hcats of formation of the alkoxy radicals involved together with AH",(NO) = 21.6 kcal/mole leads to the result D(R0-NO) = 41.5 f 1 kcal/mole. The concordance between D(thermochemica1) and D(kinetic), unlike previous kinetic studies, implies that E t = 0 =k 1 kcal/mole.

Interplay of Thermochemistry and Structural Chemistry, the Journal (Volume 14, 2003) and the Discipline

“…From the data in Ref. [101], we deduce that the corresponding difference for their nitrite isomers is 14 ± 6 kJ/mol, which is very nearly the same number. What about the corresponding pair of nitroso derivatives?…”

Conformer-specific geminate recombination following methyl nitrite photolysis in solution

“…However, the integrated absorption cross-section of gas phase nitric oxide is significantly smaller than for the corresponding terminal N-O stretching mode in methyl nitrite [28]. The 3500 cm -1 barrier for conformational interchange on the electronic ground state [18] is much smaller than the UV photon energy (>27500 cm -1 ) and the MeO-NO bond dissociation energy of 14620 ± 350 cm -1 [29]. Geminate recombination will initially deposit an excess energy in the MeONO molecule corresponding to this bond energy, and dissipation to the solvent bath over a timescale of >50 ps allows time for the cooling molecules to explore a wide conformational space before trapping into the syn or anti conformer structures.…”

Molecular Beam Study of Ethyl Nitrite Photodissociation and Unimolecular Decay of Ethoxy Fragments

“…The energy available after this first bond rupture amounts to Ea\1~26000 cm~1 (based on a dissociation energy of 14800 cm-I [7]). According to our primary P(E I ) distribution, the most probable total translational energy (of both fragments) amounts to 9800 em -1, or 38% of E avi ' This value compares favorably with the 42% predicted by an impulsive model without vibrational restrictions (see table 4 in Ref.…”