Nitroso compounds estimation

An attempt to estimate human daily impact of N nitroso compounds is shown in Table I. The apparent intake from food of preformed nitrosamines is comparatively low, at least in these surveys of a Western diet in England (3). The Intake directly to the respiratory tract from smoking could be somewhat larger. However, if the blood levels reported are confirmed as correct, then inputs of up to 700 meg per day of at least N nitrosodimethylamine (NDMA) may be calculated, based on pharmacokinetic considerations of data obtained in animals and extrapolated to man. It should be emphasized that no information is available at present on nitrosamide intake or in vivo formation, largely because of analytical limitations. 

N-Nitroso Compounds and Precursors (Human Daily Impact - Estimate)... 

In order to estimate the enthalpies of formation of nitroso compounds from the corresponding amine or nitro compounds, we derive difference quantities 855 and 855. The nitroso/amino difference quantity < 55 (NO, NH2 R) is defined by... 

Isomerization of nitroso compounds to the corresponding oxime is rapid at temperatures above the melting point of the dimer or in the presence of metallic or other reactive surfaces or in certain non-aqueous solvents . For the nitroso-methane-formaldoxime isomerization the activation energy was estimated as 30-40 kcal.mole . The thermal gas-phase isomerization of nitrosomethane, reaction (1), has been studied by a flow technique at low pressures, and found to be highly sensitive to reaction conditions, especially to the nature and extent of the surfaces. Under conditions favourable to the homogeneous gas phase process, 27.1 kcal.mole and log /l(sec ) = 8.9. The low pre-exponential factor was interpreted in terms of a cyclic transition state, viz. 

Oximes may be involved in tautomeric equilibria with nitroso compounds. The very large difference between the tautomeric forms, from the point of view of nitrogen screening as estimated (117) from the shifts of the corresponding methyl derivatives [52], [53], (Tables XXV and XXVIII), makes nitrogen NMR an attractive means of investigation... 

Bartsch, H., H. Ohshima, B. Pignatelli, and S. Cahnels Human exposure to endogenous A-nitroso compounds Quantitative estimates in subjects at high risk for cancer of the oral cavity, esophagus, stomach, and urinary bladder Cancer Surv. 8 (1989) 335-362. 

As an example, the photodegradation products of chloramphenicol (nitroso-compounds and paranitro-benzaldehyde) are considered carcinogenic. These products will be formed in vitro and in vivo and can reach the bone marrow in rats [37]. Chronic use of chloramphenicol has been coimected with bone marrow depression, not caused by chloramphenicol itself. Apart from the question if this risk is estimated well [38], it can be avoided completely if the patient covers his skin if a dermal preparation has been applied and only use chloramphenicol as eye ointment 1 % at night. See also Sect. 10.5. 

Phenolics are known to react with nitrite to form C-nitroso phenolic compounds (Mirvish, 1981 Walker et al., 1982) (Fig. 4), The strength of this reaction depends on the number of hydroxy groups and their position. A fast way to estimate the nitrite... 

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