Nitrous photolysis

The proton NMR spectrum shows chem shifts of 6.93 5.957- (Ref 1). Photolysis with a Hg arc lamp gives N, nitrous oxide, methane, and ethane (Ref 2). It was found to produce colon and rectal carcinomas in rats after oral administration at 12mg/kg weekly, induction period 235 days (Ref 3)... 

The yields of free radicals from the photolysis of nitrous acid and of aldehydes should be established. 

Photolytic. Photodegrades under simulated atmospheric conditions to phosgene and nitrosyl chloride. Photolysis of nitrosyl chloride yields chlorine and nitrous oxide (Moilanen et al., 1978 Woodrow et ah, 1983). When aqueous solution of chloropicrin (10 M) is exposed to artificial UV light (X <300 nm), protons, carbon dioxide, hydrochloric and nitric acids are formed (Castro and Belser, 1981). 

Cox, R. A., The Photolysis of Gaseous Nitrous Acid—A Technique for Obtaining Kinetic Data on Atmospheric Photooxidation Reactions, Ini. J. Chem. Kinet. Symp., 1, 379-398 (1975). 

It should be noted that only a portion of the O( D) formed generates OH via reaction (2a) the remainder is deactivated to ground-state 0(3P), reaction (2b), which then re-forms O,. For example, at 50% RH and 300 K at the earth s surface, about 10% of the O( D) formed generates OH. As a result, as discussed later in this chapter, the relative importance of (2a) decreases at higher altitudes due to the decrease in water vapor. This is also an important source in polluted areas, where, however, there are additional sources as well. These include the photolysis of gaseous nitrous acid (HONO) and hydrogen peroxide (H202) ... 

In a similar manner, 11/3-nitrites, on photolysis, attack Ci to furnish the corresponding oximes which, upon nitrous acid treatment, gave 18-oxygenated steroids. The most spectacular application of the Barton reaction has been a three-step synthesis of aldosterone.12 Irradiation of corticosterone-11-nitrite (27, R = NO), followed by nitrous acid treatment, gave aldosterone (29) in 15% overall yield. Comparable conversions of 11/3-hydroxyprogesterone to 21-desoxyaldosterone12 and A1-corticosterone to A aldosterone14 have also been achieved. 

At 298 K and atmospheric pressure with 50% relative humidity, about 0.2 HO" are produced per O( D) atom formed. Photolysis of 03 in the presence of water vapor is the major tropospheric source of HO", particularly in the lower troposphere where water vapor mixing ratios are high (for an explanation of the term mixing ratio see below). Other sources of HO" in the troposphere include the photolysis of nitrous acid (HONO), the photolysis of formaldehyde and other carbonyls in the presence of NO, and the dark reactions of 03 with alkanes. Note that all these processes involve quite complicated reaction schemes. For a discussion of these reaction schemes we refer to the literature (e.g., Atkinson, 2000). 

The OH (X2n) can be generated from the photolysis of water, hydrogen peroxide, and nitric and nitrous acid. Reactions of OH(A2n) with various hydrocarbons arc important in understanding photochemical smog formation (see Section VIII—2). 

The photochemical processes of triatomic molecules have been extensively studied in recent years, particularly those of water, carbon dioxide, nitrous oxide, nitrogen dioxide, ozone, and sulfur dioxide, as they are important minor constituents of the earth s atmosphere. (Probably more than 200 papers on ozone photolysis alone have been published in the last decade.) Carbon dioxide is the major component of the Mars and Venus atmospheres. The primary photofragments produced and their subsequent reactions are well understood for the above-mentioned six triatomic molecules as the photodissociation involves only two bonds to be ruptured and two fragments formed in various electronic states. The photochemical processes of these six molecules are discussed in detail in the following sections. They illustrate how the knowledge of primary products and their subsequent reactions have aided in interpreting the results obtained by the traditional end product analysis and quantum yield measurements. 

A flow apparatus for detroying 98% of the w-dissolved RDX at flow rates of 2500fi/min is described in Ref 114. The photolysis products include nitrogen gas, nitrous oxide gas. nitrate and nitrite ions, formaldehyde and ammonia. One intermediate product has been identified as l-nitroso-3,5-dimtro-l,3,5-triazacyclohexane. The primary photochemical steps involved in the photolysis are postulated... 

The racemic acid 399 was treated with oxalyl chloride to afford an acyl chloride 401, which on reaction with anhydrous hydrazine yielded the hydra-zide 402. The latter was converted to the azide 403 by treatment with nitrous acid. Photolysis of 403 which a high-pressure mercury lamp afforded the lactam 404. This lactam was synthesized earlier by Japanese chemists by an entirely different method (187). 

The importance of conformation in selective attack of the 1 l/ -alkoxy radical on C18 and C19 was nicely illustrated by the photolysis of the nitrite 18 derived from the dienone 19. This afforded only C18 attack.7 Treatment of the derived oxime with nitrous acid gave 1-dehydro-aldosterone acetate 20. This is a convenient precursor for labelled aldosterone acetate since selective hydrogenation with tritium gives 1,2-ditritiated aldosterone acetate. 

The ratio of nitrogen formed in the photolysis of pure N20 to that formed under identical conditions in a nitrous oxide-ethane mixture is... 

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