A theoretical comparison of phosphino and amino groups in the isocyanide–cyanide rearrangement

Nguyen, Minh Tho; Groarke, Peter J.; Malone, Seamus; Hegarty, A. F.

doi:10.1039/p29940000807

Cited by 16 publications

(9 citation statements)

References 24 publications

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“…On the other hand, the reverse of route C suggests the existence of an energetically feasible channel for the conversion of HNC into HCN from the initially formed energised adduct 3 . Note that the unimolecular conversion HNC → HCN is associated with an energy barrier of about 30 kcal/mol, relative to HNC . In this sense, the isonitrile−nitrile conversion will be greatly facilitated in the presence of the hydrogen atom.…”

Section: Resultsmentioning

confidence: 99%

“…Consequently, in the isolated HCN molecule, the dissociation pathway is unimportant, and in fact, its isomerization to HNC is the only predominant channel. This isomerization has been shown to have a barrier of about 47.5 kcal/mole, and it provides a facile unimolecular reaction pathway for the relatively stable HCN moiety. Lin et al reported a computed rate constant (3.5 × 10 13 exp(−23750/ T ) s -1 ) for this isomerisation.…”

Section: Introductionmentioning

confidence: 99%

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A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States

Sumathi

Nguyen

1998

J. Phys. Chem. A

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Ab initio molecular orbital calculations at the second-order perturbation theory (UMP2) and coupled cluster singles and doubles with corrected triples (CCSD(T)) levels with 6-311++G(d,p) and 6-311++G(3df,3dp) basis sets have been carried out to construct the potential energy surfaces related to the various reactions of the [CH2N] system, including H2+CN, H+HCN, and H+HNC in both lowest lying doublet and quartet electronic states. Barrier heights, vibrational wavenumbers, and moments of inertia were then utilized in the calculations of rate constants using a quantum Rice−Ramsperger−Kassel (QRRK) theory. The calculated total rate constant k ∞ for the H+HCN reaction at 300 K is 2.2 × 107 cm3 mol-1 s-1 and is suggestive of a slow reaction and it corresponds predominantly to the stabilization of the adducts. On the other hand, the H+HNC reaction is calculated to be a pressure-independent fast reaction with a rate coefficient of 1.9 × 1011 cm3 mol-1 s-1 leading primarily to H+HCN dissociation products. The standard heat of formation of the H2CN radical is estimated to be Δ = 56 ± 3 kcal/mol (57 ± 3 kcal/mol at 0 K).

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States

Sumathi

Nguyen

1998

J. Phys. Chem. A

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“…The barrier for this process is ca. 30 kcal/mol, , and the enthalpy of formation difference between HNC and HCN is close to 14 kcal/mol. , This means that the thermal decomposition of methyl azide under FVP conditions can yield chemically activated CH 2 NH and chemically activated HNC, which finally isomerizes to HCN. The tautomerization of HNC to HCN will also be facilitated by collisions with the walls of the pyrolysis tube.…”

Section: Azidesmentioning

confidence: 99%

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

2017

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Flash vacuum pyrolysis (FVP) of azides is an extremely valuable method of generating nitrenes and studying their thermal rearrangements. The nitrenes can in many cases be isolated in low-temperature matrices and observed spectroscopically. NH and methyl, alkyl, aralkyl, vinyl, cyano, aryl and N-heteroaryl, acyl, carbamoyl, alkoxycarbonyl, imidoyl, boryl, silyl, phosphonyl, and sulfonyl nitrenes are included. FVP of triazoloazines generates diazomethylazines and azinylcarbenes, which often rearrange to the energetically more stable arylnitrenes. N elimination from monocyclic 1,2,3-triazoles can generate iminocarbenes, 1H-azirines, ketenimines, and cyclization products, and 1,2,4-triazoles are precursors of nitrile ylides. Benzotriazoles are preparatively useful precursors of cyanocyclopentadienes, carbazoles, and aza-analogues. FVP of 5-aryltetrazoles can result in double N elimination with formation of arylcarbenes or of heteroarylcarbenes, which again rearrange to arylnitrenes. Many 5-substituted and 2,5-disubstituted tetrazoles are excellent precursors of nitrile imines (propargylic, allenic, or carbenic), which are isolable at low temperatures in some cases (e.g., aryl- and silylnitrile imines) or rearrange to carbodiimides. 1,5-Disubstituted tetrazoles are precursors of imidoylnitrenes, which also rearrange to carbodiimides or add intramolecularly to aryl substituents to yield indazoles and related compounds. Where relevant for the mechanistic understanding, pyrolysis under flow conditions or in solution or the solid state will be mentioned. Results of photolysis reactions and computational chemistry complementing the FVP results will also be mentioned in several places.

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“…Migration of an amino group requires a comparable activation energy whereas that of a phosphino group is a more facile process. 42 It is of interest to compare the 1,2-migration around a CÈN moiety of the carbon-centered CN, CCH and CP groups that all carry a triple bond. Fig.…”

Section: The Isocyanophosphapropyne-cyanophosphapropyne Isomerisationmentioning

confidence: 99%

Theoretical study of cyanophosphapropyne (NCCP), isocyanophosphapropyne (CNCP) and their isomers: stability and properties

Tran

Hajgató

Veszprémi

et al. 2001

Phys. Chem. Chem. Phys.

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A theoretical comparison of phosphino and amino groups in the isocyanide–cyanide rearrangement

Cited by 16 publications

References 24 publications

A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States

A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Theoretical study of cyanophosphapropyne (NCCP), isocyanophosphapropyne (CNCP) and their isomers: stability and properties

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A theoretical comparison of phosphino and amino groups in the isocyanide–cyanide rearrangement

Cited by 16 publications

References 24 publications

A Theoretical Study of the CH2N System: Reactions in both Lowest Lying Doublet and Quartet States

A Theoretical Study of the CH2N System: Reactions in both Lowest Lying Doublet and Quartet States

Flash Vacuum Pyrolysis of Azides, Triazoles, and Tetrazoles

Theoretical study of cyanophosphapropyne (NCCP), isocyanophosphapropyne (CNCP) and their isomers: stability and properties

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A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States

A Theoretical Study of the CH₂N System: Reactions in both Lowest Lying Doublet and Quartet States