Photochemical behaviour of cyclic <i>s‐cis</i> α‐oxo oxime ethers. <i>Ab‐initio</i> investigation on ethanedial monooxime as model compound

Stunnenberg, F.; Rexwinkel, Roel B.; Cerfontain, H.; Sevin, A.

doi:10.1002/recl.19901091003

Cited by 10 publications

(3 citation statements)

References 40 publications

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“…24 The photodegradation of oxime species may also compete with the photoisomerization mechanism. Experimental analyses 1,3,[10][11][12][13][14][15] and theoretical studies 18 of photodegradation products gave evidence of N-O bond dissociation as one of the main degradation pathway. The photodissociation mechanism of the N-O bond can proceed through conical intersections that arise from the diabatic crossing of excited singlet states that have signicantly different electronic character (p/p* and s NO /s * NO ).…”

Section: Computational Results and Discussionmentioning

confidence: 99%

“…The S 1 state may have n/π* 18 or π/ π* character. 18 If a local minimum energy structure is found in the S 1 state, an activation energy barrier is expected for N-O bond dissociation. The geometry of the minimum energy structure in T 1 is one where δ~90 deg (see Figure 1 for definition of δ).…”

Section: Computational Results and Discussionmentioning

confidence: 99%

“…The photodissociation mechanism of the N-O bond can proceed through conical intersections that arise from the diabatic crossing of excited singlet states that have signicantly different electronic character (p/p* and s NO /s * NO ). 18 If a local minimum energy structure is found in the S 1 state, an activation energy barrier is expected for N-O bond dissociation. Photodissociation may also be obtained through intersystem crossing.…”

Section: Computational Results and Discussionmentioning

confidence: 99%

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Phototransformation of tetrazoline oxime ethers – part 2: theoretical investigation

et al. 2016

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The competitive photoisomerization and photodegradation reactions of a tetrazoline oxime ether showing important fungicidal activity are investigated by Time Dependent-Density Functional Theory (TD-DFT) and Complete Active Space Self-Consistent Field (CASSCF) calculations of ground state and excited state (singlet, S and triplet, T) potential energy surfaces.Two key experimental results reported previously 1 are explained in this study: 1) why only E isomers undergo N-O bond scission and photodegradation and 2) what is the mechanism for deactivation of the Z isomers. In addition, the reactive pathway that involves intersystem crossing is shown to be competitive with reactions in the singlet state. Our results demonstrate that the photoreactivity (photodegradation or photoisomerization) of the eight conformers 2 studied here is clearly related to differences between the respective electronic configurations of the lowest singlet excited state. It is shown that the addition of a bulky substituent on the pyridyl group prevents E isomers from being photodegraded.The photodegradation mechanism. The cis/trans C=N photoisomerization and photodegradation mechanisms were investigated by quantum calculations. 16 TD-DFT calculations were performed for Z and E at the B3LYP/6-31+G(d,p) level to obtain electronic

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Section: Computational Results and Discussionmentioning

confidence: 99%

Section: Computational Results and Discussionmentioning

confidence: 99%

Section: Computational Results and Discussionmentioning

confidence: 99%

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Phototransformation of tetrazoline oxime ethers – part 2: theoretical investigation

et al. 2016

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Light‐Induced Chemistry of Oximes and Derivatives

Roth¹

2010

Patai's Chemistry of Functional Groups

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Photoreactions of oximes have been known for 120 years. The earliest recognized reaction was geometric isomerization, which is still the most prominent oxime photoreaction; it proceeds via a ππ* triplet state. More than sixty years later the intriguing photo‐Beckmann rearrangement came to light, a C–C=N–O to O=C–N–C conversion, generating, for example, ɛ‐caprolactam from cyclohexanone ξιμɛ. The rearrangement proceeds via a ππ* singlet state forming an oxazirane intermediate; the oxazirane ring usually opens in stereospecific fashion. Detailed insight into the stereo‐ and regiochemistry of the rearrangement was gained from steroidal oximes, the most thoroughly investigated class of oximes. Additional photoreactions of oximes or of their ethers and esters include: net loss of hydroxylamine generating carbonyl compounds; loss of water from aldoximes forming nitriles; conversion of ketoximes to nitriles by more complex mechanisms; photochemical O–H cleavage generating iminoxyl radicals, an interesting family of free radicals; N–O cleavage giving rise to iminyl radials, which undergo radical cyclizations. β,γ‐Unsaturated oximes undergo aza‐di‐π‐methane rearrangements, cyclize to oxazolines, and undergo further reorganizations. The palette of oxime reactions has been further enriched by triplet energy transfer or electron transfer sensitization; oximes serve as electron donors or acceptors.

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ChemInform Abstract: Photochemistry of α‐Oxo Oximes. Part 12. Photochemical Behaviour of Cyclic s‐cis α‐Oxo Oxime Ethers. Ab initio Investigation on Ethanedial Monooxime as Model Compound.

et al. 1991

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Photochemical behaviour of cyclic s‐cis α‐oxo oxime ethers. Ab‐initio investigation on ethanedial monooxime as model compound

Cited by 10 publications

References 40 publications

Phototransformation of tetrazoline oxime ethers – part 2: theoretical investigation

Phototransformation of tetrazoline oxime ethers – part 2: theoretical investigation

Light‐Induced Chemistry of Oximes and Derivatives

ChemInform Abstract: Photochemistry of α‐Oxo Oximes. Part 12. Photochemical Behaviour of Cyclic s‐cis α‐Oxo Oxime Ethers. Ab initio Investigation on Ethanedial Monooxime as Model Compound.

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