Nitrous acid, oxidation

Ellagic acid concentration can be determined through an oxidation reaction with nitrous acid, and two methods have been described by Bate-Smith (1977) and by Wilson and Hagerman (1990), respectively. 

Scalbert et al. (1989) summarized the method of Bate-Smith (1977) In a tube sealed with a Teflon-lined screw cap, 0.2 mL of the aqueous plant extract (1 mL if the extract is not very concentrated) is added to 1.8 mL of 1 1 methanol/water (1 mL of 9 1 methanol/water if the sample is not concentrated) and 0.16 mL of aqueous 6% (v/v) acetic acid. Nitrogen is 

Wilson and Hagerman (1990) described an alternative spectrophoto metric procedure to quantify ellagic acid. This method has three advantages over the procedure developed by Bate-Smith (1977) 1) it is not sensitive to gallic acid, which can result in an overestimate of the ellagitannin content, 2) it is more sensitive, and 3) it is more convenient because oxygen does not interfere with the reaction. 

This procedure is based on the formation of the electophile NO+, which can react with an ellagic acid residue (4.2) at two sites, either via a substitution reaction which results in 4.3, or an addition reaction that results in the nitrosyl dienone 4.4. These compounds can decay to form the quinine oxime 4.5, which under alkaline conditions forms the red product 4.6. When related compounds, such as gallic acid, phloroglucinol, hydroxycinnamic acids, and phenol are subjected to this assay, a yellow-brown product is formed, which does not interfere with the spectrophotometric detection of ellagic acid. 

---

When 6/3-aminopenicillanic acid (6-APA) is diazotized in the presence of chloride ion, the principal product obtained is 6a-chloropenicillanic acid (38) (62JOC2668), presumably by way of the diazo intermediate (39 Scheme 29) (72JCS(P1)895). If the diazotization is carried out in the presence of excess bromide instead of chloride, significant amounts of the 6,6-dibromo derivative are obtained, and in the case of excess iodide the 6,6-diiodopenicillanic acid becomes the predominant product (69JCS(C)2123). The 6,6-dihalo products presumably arise from nitrous acid oxidation of halide to halogen, which then reacts with (39). 

Hydrazoic acid reacts with potassium permanganate. They mutually reduce each other to evolve a mixture of nitrogen and oxygen. Nitrous acid oxidizes hydrazoic acid with the evolution of nitrogen. 

Nitrous acid oxidizes hydrazoic acid with the evolution of nitrogen. A dilute solution of nitric or acetic acid, in which a little sodium nitrite has been dissolved, dissolves and destroys lead azide. Such a solution may conveniently be used for washing floors, benches, etc., on which lead azide may have been spilled. 

Hq8 1.4785. It was prepd from thiosemicar-bazide and /S-ethoxypropionyl chloride, followed by nitrous acid oxidation of the intermediate thio (Ref 2)... 

Iodine and Ce(IV) salts reduce HN3 to dinitrogen. Nitrous acid oxidizes hydrazoic acid to dinitrogen and dinitrogen oxide ... 

With a-di ketones 1- and 2-amino- and 1,2- and 1,5-diaminoimidazoles condense to give fused-ring heterocycles, with initial attack at the C-amino function. An N-amino group can be removed by treatment with nitrous acid. Oxidation of quaternary salts of 1-aminoimidazoles gives azoimidazolium salts, while manganese dioxide converts 1,2-di-aminoimidazoles into triazoles and triazines (see Section IV,D). 

Normorphine cannot be prepared like norcodeine, through the N-nitrosocompound, as nitrous acid oxidizes morphine to pseudomorphine [557]. Conversion of morphine-N-oxide to normorphine by dichromates is unsatisfactory owing to breakdown of the ring structure [556],... 

Add dropwise 1 % NaNO with constant stirring at 4 C. Large excess of NaNO should be avoided. This can be checked with starch-iodide paper or, alternatively, with 1% starch and 50 mM KI on a white tile. Free nitrous acid oxidizes iodide to iodine which reacts with starch to give a blue-black color. 

Precaution Combustible exposed to heat or flame may burn, but does not readily ignite DOT keep away from food containers may explode in fire incompat. with nitrous acid, oxidizing agents reduces warm ammoniacal silver nitrate... 

Isonicotinanilide, 116 Isonlcotinic acid, bacterial oxidation of, 860 Isoprene, reaction with chloro-sulfonyl isocyanate, 617 2-Isopropanyl-3-p /ridi.nol, nitrous acid oxidation of,... 

The glycamines may serve as intermediates in the s3mthesis of 2-deoxy-sugars. 2-Deoxy-D-ribose was prepared by nitrous acid oxidation of 2-amino-2-deoxyribitol (SS8), obtained from D-arabinose and D-ribulose. 

Propidium is supplied by Calbiochem as the diiodide salt. It is necessary to remove the iodide prior to diazotization because nitrous acid oxidizes iodide to iodine. Removal can be accomplished by dissolving the propidium in water and applying it to a carboxymethyl cellulose column. The column is washed with water until I" no longer elutes. Iodide can be detected by adding nitrous acid to the beaker collecting the eluent and noting the formation of dark yellow or tan iodine. The propidium is eluted with dilute HCl at pH 1.5 to 2.0. The HCl then serves as the... 

---