Photolysis of <i>N</i>‐nitrosamines in neutral media

Fiz, Nemesio; Usero, J.L.; Casado, Julio

doi:10.1002/kin.550250503

Cited by 13 publications

(16 citation statements)

References 18 publications

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“…It has been proposed that the dimethylaminyl radical may abstract a H-atom from another NDMA molecule, leading to DMA and the C-centered radical 7, which rearranges to methylidenemethylamine 6 by losing the NO fragment [21] [22].…”

Section: Scheme 2 Generation Of the Intermediate By-products During mentioning

confidence: 99%

UV Direct Photolysis of N-Nitrosodimethylamine (NDMA): Kinetic and Product Study

Stefan¹,

Bolton²

2002

HCA

151

133

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Dedicated to Professor Andre¬ M. Braun on the occasion of his 60th birthdayThe ultraviolet (UV) direct photolysis of N-nitrosodimethylamine (NDMA) in aqueous solutions at pH 3 and 7 leads to dimethylamine, and nitrite and nitrate ions as the major degradation products. In addition, small amounts of formaldehyde, formic acid, and methylamine are formed. When the initial concentration of NDMA was 1 mm, only a 13% decrease in the total organic carbon (TOC) was measured at pH 7, whereas no significant change in the TOC was observed at pH 3. In the concentration range 0.01 ± 1 mm NDMA, zero-order kinetics is obeyed, whereas first-order kinetics is followed at concentrations below 0.01 mm. The photolysis occurs much faster at pH 3 than at pH 7, which is explained by the difference in the quantum yields of the process at these two pH values. UV Direct photolysis is an efficient process for the removal of NDMA from contaminated waters, and electrical energy per order (E EO ) values as low as 0.3 ± 0.5 kWh/order/m 3 were calculated for treatment of low concentrations of NDMA (0.001 mm).

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Section: Scheme 2 Generation Of the Intermediate By-products During mentioning

confidence: 99%

UV Direct Photolysis of N-Nitrosodimethylamine (NDMA): Kinetic and Product Study

Stefan¹,

Bolton²

2002

HCA

151

133

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“…Studies of the kinetics of the photodecomposition in neutral and acidic solutions provided first insight into the mechanism of N-N bond rupture in condensed phase already in the early 1980s. [3][4][5] Photolysis experiments in a flow cell have been reported for dimethylnitrosamine (DMN). 6,7 The photolysis was initiated by excitation with either an excimer laser (308 nm) or with the lines at 363.5 and 248.1 nm of a Hg lamp.…”

Section: Introductionmentioning

confidence: 99%

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

Wenge

Kensy

Dick

2010

Phys. Chem. Chem. Phys.

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The photodissociation reaction of N-nitrosopyrrolidine isolated and cooled in a supersonic jet has been studied following excitation to the S(1) and S(2) electronic states. The nascent NO (X[combining tilde] (2)Pi((1/2),3/2), v, j) radicals were ionized by state-selective (1 + 1)-REMPI via the A(2)Sigma(+) state. The angularly resolved velocity distribution of these ions was measured with the velocity-map imaging (VMI) technique. Photodissociation from S(1) produces NO in the vibrational ground state and the pyrrolidine radical in the electronic ground state 1 (2)B. About 73% of the excess energy is converted into kinetic energy of the fragments. The velocity distribution shows a strong negative anisotropy (beta = -0.9) in accordance with the npi*-character of the S(0)--> S(1) transition. An upper limit for the N-NO dissociation energy of (14 640 +/- 340) cm(-1) is determined. We conclude that photodissociation from S(1) occurs very fast on a completely repulsive potential energy surface. Excitation into the S(2)pipi*-state leads to a bimodal velocity distribution. Two dissociation channels can be distinguished which show both positive anisotropy (beta = 1.3 and 1.6) but differ considerably in the total kinetic energy and the rotational energy of the NO fragment. We assign one channel to the direct dissociation on the S(2) potential energy surface, leading to pyrrolidine radicals in the excited electronic state 1 (2)A. The second channel leads to pyrrolidine in the electronic ground state 1 (2)B, presumably after crossing to the S(1) state via a conical intersection.

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“…In contrast, the sample exposed to near‐UV radiation does deteriorate over time (albeit slowly). There is precedent for nitrosamine degradation by photolysis,17, 28, 29 however, the quantum yield for photodissociation is often low due to the rapid recombination of the alkylaminyl radical and NO which are generated during this process. This aspect of nitrosamine degradation is currently being investigated in our laboratories.…”

Section: Resultsmentioning

confidence: 99%

“…of amine. This number is dependent on the propensity of the amine (18,28) to form a carbamate derivative, in this case piperazine-1-carboxylate, and its susceptibility to hydrolysis. The hydrolysis reaction produces HCO À 3 while regenerating piperazine.…”

Section: Resultsmentioning

confidence: 99%

N‐Nitrosopiperazines form at high pH in post‐combustion capture solutions containing piperazine: a low‐energy collisional behaviour study

Jackson

Attalla

2010

Rapid Comm Mass Spectrometry

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During the process of exploring aqueous piperazine chemistry under simulated flue-gas scrubbing conditions, positive-ion electrospray ionisation mass spectrometric (ESI-MS) analyses of the resulting reaction mixtures in a triple quadrupole system revealed the presence of peaks at m/z 116 and 145, the putative N-nitroso derivatives of piperazine. Confirmation of the presence of these species in the reaction mixtures was achieved using collision-induced dissociation experiments. A purchased standard, together with in-house synthesised N-nitrosopiperazine standards (including N-nitroso derivatives derived from deuterium-labelled precursor materials), were used for this purpose. Across a small range of collision energies, large fluctuations in the abundance of the two major product ions of protonated N-nitrosopiperazine, m/z 86 and 85, were observed. Using B3LYP/6-311 + +G(d,p) computations, the potential energy surface was determined for loss of NO and [H,N,O]. At an activation energy slightly in excess of 1 eV, intramolecular isomerisation precedes loss of NO (m/z 86) via a 4,1 H-shift, and at activation energies between 2.1-2.3 eV, consecutive loss of NO and atomic hydrogen competes with the direct loss of nitrosyl hydride (m/z 85). It is recommended that any multiple reaction monitoring method for quantifying N-nitrosopiperazines at low collision energies use the sum of both transitions (m/z 116 ← 85, m/z 116 ← 86) to avoid errors that could be introduced by subtle changes in ES source conditions or collision voltages. This approach is adopted in an HPLC/MS/MS method used to monitor the degradation of N-nitrosopiperazine exposed to (i) broad-band UV light and (ii) heat typical of an amine regeneration (stripper) tower. The results reveal that aqueous N-nitrosopiperazine is thermally stable at 150°C but will degrade slowly upon exposure to UV light.

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Photolysis of N‐nitrosamines in neutral media

Cited by 13 publications

References 18 publications

UV Direct Photolysis of N-Nitrosodimethylamine (NDMA): Kinetic and Product Study

UV Direct Photolysis of N-Nitrosodimethylamine (NDMA): Kinetic and Product Study

The photodissociation dynamics of N-nitrosopyrrolidine from the first and second excited singlet states studied by velocity map imaging

N‐Nitrosopiperazines form at high pH in post‐combustion capture solutions containing piperazine: a low‐energy collisional behaviour study

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