On the singlet and triplet excited states of nitrosamines

Chow, Yuan L.; Wu, Zheng Zhi; Lau, M. P.; Yip, Rodrick W.

doi:10.1021/ja00312a064

Cited by 33 publications

(51 citation statements)

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“…13 On the S 1 excited surface, CASSCF calculations show that N-nitrosodimethylamine can lose NO· by loss of R 2 N−NO planarity, 20,24 where subsequent reactions were stymied due to high-energy barriers so that recombination of NO· and R 2 N· is favored and regenerates ground-state nitrosamine. When originating from the S 1 state, aminyl radicals can have lifetimes (τ) upward of 0.5 s. 16 Consistent with a long lifetime, Geiger et al found that UV photolysis of N-nitrosodimethylamine led to isotopic exchange for 15 NO· from the S 0 → S 1 transition but not the S 0 → S 2 transition. 25,26 Chow et al 16 also found that excitation Nnitrosodimethylamine to S 2 led to NO· release and products such as imines (CH 2 NHCH 3 and CH 2 NH) and a methyl radical (CH 3 ·).…”

Section: ■ Introductionmentioning

confidence: 95%

“…When originating from the S 1 state, aminyl radicals can have lifetimes (τ) upward of 0.5 s. 16 Consistent with a long lifetime, Geiger et al found that UV photolysis of N-nitrosodimethylamine led to isotopic exchange for 15 NO· from the S 0 → S 1 transition but not the S 0 → S 2 transition. 25,26 Chow et al 16 also found that excitation Nnitrosodimethylamine to S 2 led to NO· release and products such as imines (CH 2 NHCH 3 and CH 2 NH) and a methyl radical (CH 3 ·). Photolysis of N-nitrosopiperidine also yielded imines.…”

Section: ■ Introductionmentioning

confidence: 95%

“…20 Chow et al. 16 also found a direct excitation route [S 0 → T 1 (n → π*) transition] for N-nitrosodimethylamine at 453 nm. The photolysis of alkyl nitrosamines leads to NO· release and aminyl radicals or aminium radical cations after protonation 20,21 in the presence of acid.…”

Section: ■ Introductionmentioning

confidence: 96%

“…Photolysis of N-nitrosopiperidine also yielded imines. 11,16 On the other hand, UV photolysis of 1 started with NO· release and led to Ph 2 NH and, after extended photolysis, carbazole as a secondary product. Photorelease of NO· has been recognized in other compounds, such as diazeniumdiolates.…”

Section: ■ Introductionmentioning

confidence: 99%

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Mechanism of Photochemical O-Atom Exchange in Nitrosamines with Molecular Oxygen

et al. 2015

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The detection of an oxygen-atom photoexchange process of N-nitrosamines is reported. The photolysis of four nitrosamines (N-nitrosodiphenylamine 1, N-nitroso-N-methylaniline 2, N-butyl-N-(4-hydroxybutyl)nitrosamine 3, and N-nitrosodiethylamine 4) with ultraviolet light was examined in an (18)O2-enriched atmosphere in solution. HPLC/MS and HPLC-MS/MS data show that (18)O-labeled nitrosamines were generated for 1 and 2. In contrast, nitrosamines 3 and 4 do not exchange the (18)O label and instead decomposed to amines and/or imines under the conditions. For 1 and 2, the (18)O atom was found not to be introduced by moisture or by singlet oxygen [(18)((1)O2 (1)Δg)] produced thermally by (18)O-(18)O labeled endoperoxide of N,N'-di(2,3-hydroxypropyl)-1,4-naphthalene dipropanamide (DHPN(18)O2) or by visible-light sensitization. A density functional theory study of the structures and energetics of peroxy intermediates arising from reaction of nitrosamines with O2 is also presented. A reversible head-to-tail dimerization of the O-nitrooxide to the 1,2,3,5,6,7-hexaoxadiazocane (30 kcal/mol barrier) with extrusion of O═(18)O accounts for exchange of the oxygen atom label. The unimolecular cyclization of O-nitrooxide to 1,2,3,4-trioxazetidine (46 kcal/mol barrier) followed by a retro [2 + 2] reaction is an alternative, but higher energy process. Both pathways would require the photoexcitation of the nitrooxide.

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Section: ■ Introductionmentioning

confidence: 95%

Section: ■ Introductionmentioning

confidence: 95%

Section: ■ Introductionmentioning

confidence: 96%

Section: ■ Introductionmentioning

confidence: 99%

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Mechanism of Photochemical O-Atom Exchange in Nitrosamines with Molecular Oxygen

et al. 2015

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“…According to Ref. [ ] a nitrosamine‐acid complex bonded to DMNA via O atom is the photoactive species.…”

Section: Introductionmentioning

confidence: 99%

Solvent effect on the tautomers' stabilities of protonated N,N‐dimethylnitrosamine: The role of hydrogen bonds network

Andrade

Ventura

Monte

2016

Int J of Quantum Chemistry

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DFT calculations have been applied in order to study the free energies of the structures corresponding to the three different protonation sites of N,N‐dimethylnitrosamine (DMNA). The solvent effect has been taken into account through the study of clusters consisting of protonated DMNA and up to four explicit water molecules, either in the absence or in the presence of a continuum (CPCM) solvation model. Addition of water molecules has been done by a careful screening procedure through which all important hydrogen bonds are likely to be considered. Protonation of DMNA makes all their lone pairs no longer available for hydrogen bond formation with water molecules, such that hydrogen bonds have been observed, for almost all structures, only between water molecules and between one water molecule and the protonated DMNA, in this latter case intermediated by the proton. The stabilities of the solvated structures are governed not only by the number of hydrogen bonds but also by the positions of the water molecules involved in these bonds, as well as by which of them donate or accept H atoms. Our results indicate that oxygen protonation is the most favorable one, regardless of the presence of water molecules. In vacuum protonation at the N‐amino (2a) is approximately as favorable as protonation at the N nitroso (2c). However, in water the former protonation is by far the less favorable one. Our best estimates for the ΔG values in bulk solvent are: ΔG(2a) ≈ 17.9, ΔG(1c) ≈ 4.3, and ΔG(2c) ≈ 4.9 kcal/mol.

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Photochemistry of Nitro and Nitroso Compounds

Chow

2009

Patai's Chemistry of Functional Groups

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Introduction Photochemistry of Aromatic Nitro Compounds Photochemistry of Nitro‐Olefins Photochemistry of Aliphatic Nitro Compounds Photochemistry of C ‐Nitroso Compounds Photochemistry of Alkyl Nitrites Photochemistry of N ‐Nitro and N ‐Nitroso Compounds

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On the singlet and triplet excited states of nitrosamines

Cited by 33 publications

References 0 publications

Mechanism of Photochemical O-Atom Exchange in Nitrosamines with Molecular Oxygen

Mechanism of Photochemical O-Atom Exchange in Nitrosamines with Molecular Oxygen

Solvent effect on the tautomers' stabilities of protonated N,N‐dimethylnitrosamine: The role of hydrogen bonds network

Photochemistry of Nitro and Nitroso Compounds

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