Azide determination

Figure 1. Apparatus for lead azide determination using the nitrogen evolution method [3], A, 125-ml flat-bottom reaction flask B, 1.4 X 4.5-cm vial C, 125-ml flat-bottom absorption flask D, water reservoir E, 500-ml gas buret F, water jacket H, 50-ml buret I, 3-way T-stopcock, position B J, 3-way T-stopcock, position A K, thermometers L, leveling bulb.

Azide-tetrazole isomerization has been studied by NMR spee-troseopy for 2-azidothiazolo[5,4-h]- and 2-azidothiazolo[4,5-c]pyridines, and the equilibrium eonstants were determined at various temperatures (77JHC1045). 

Iodine azide, generated in situ from an excess of sodium azide and iodine monochloride in acetonitrile, adds to ethyl l//-azepine-l-carboxylate at the C4 — C5 and C2 —C3 positions to yield a 10 1 mixture of the rw-diazidodihydro-l//-azepines 1 and 2, respectively.278 The as stereochemistry of the products is thought to be the result of initial trans addition of the iodine azide followed by an SN2 azido-deiodination. The diazides were isolated and their stereochemistry determined by conversion to their bis-l,3-dipolar cycloadducts with dimethyl acetylene-dicarboxylate. 

Kaye, An Electron Microscope Method for the Determination of the Particle Size Distribution and Particle Shape of Colloidal and Ball-Milled Lead Azide , PATR 2133 (1955) 25a) A.T. 

The question as to whether or not hydrazoic add and nitric add are more closely related to the corresponding covalent compounds than to the ions could be answered by determining the configurations of the acids. From general information we would predict that the H-N and H-0 bonds are essentially covalent (with perhaps about one-third ionic character) and that the Ns and NOs groups in the acids have the same structures as in methyl azide and nitrates. This prediction is supported by the instability of the acids. 

The nature of the group X determines the type of reaction which is the most important. For X = azide, thiocyanate, hydroxide, chloride bromide and iodide the inner-sphere bath operates while for X = ammonia or oxyanions (including carboxylates) the main pathway is the outer-sphere reaction. For X = fluoride or nitrite the concentration of the cyanide ion present determines which is the major reaction pathway. 

With a view to determining the equilibrium constant for the isomerisation, the rates of reduction of an equilibrium mixture of cis- and rra/i5-Co(NH3)4(OH2)N3 with Fe have been measured by Haim S . At Fe concentrations above 1.5 X 10 M the reaction with Fe is too rapid for equilibrium to be established between cis and trans isomers, and two rates are observed. For Fe concentrations below 1 X lO M, however, equilibrium between cis and trans forms is maintained and only one rate is observed. Detailed analysis of the rate data yields the individual rate coefficients for the reduction of the trans and cis isomers by Fe (24 l.mole sec and 0.355 l.mole .sec ) as well as the rate coefficient and equilibrium constant for the cw to trans isomerisation (1.42 x 10 sec and 0.22, respectively). All these results apply at perchlorate concentrations of 0.50 M and at 25 °C. Rate coefficients for the reduction of various azidoammine-cobalt(lll) complexes are collected in Table 12. Haim discusses the implications of these results on the basis that all these systems make use of azide bridges. The effect of substitution in Co(III) by a non-bridging ligand is remarkable in terms of reactivity towards Fe . The order of reactivity, trans-Co(NH3)4(OH2)N3 + > rra/is-Co(NH3)4(N3)2" > Co(NH3)sN3 +, is at va-... 

Gel Filtration. The lyophilized protein was redissolved in 50 mM phosphate buffer, pH 7.4 0.15 m NaCl 0.013 % sodium azide and loaded on a Superdex 75HR1030 column equilibrated with the same buffer. Elution was downward flow (0.15 ml/min) and 0.25 ml fi actions were collected. Fractions with pectin lyase activity were combined, dialyzed against distilled water and used in the next step. To estimate the molecular mass of PNL, the column was calibrated with standard proteins (Sigma MW-GF-70 Albumin, 66,000 Da Carbonic Anhidrase, 29,00 Cytochrome, 12,400 and Aprotinin, 6,500). The proteins were eluted in the conditions described above and their volumes (F ) were calculated fi om the peak maximum of the absorbance at 280 nm. The partition coefficient was obtained fi om the relationship where F, represents the bed volmne of column and F the void volume (which was calculated using blue dextran. Sigma). The molecular mass was determined using a standard curve of vs the logarithm of the molecular masses of the standards [28, 29]... 

The concept of a biocatalytic membrane electrode has been extended to the use of a tissue slice as the catalytic layer. An example of this approach is an electrode for AMP which consists of a slice of rabbit muscle adjacent to an ammonia gas electrode. NHj is produced by enzymatic action of rabbit muscle constituents on AMP The electrode exhibits a linear range of 1.4 x 10 to 1.0 x 10 M with a response time varying from 2.5 to 8.5 min, depending on the concentration. Electrode lifetime is about 28 days when stored between use in buffer with sodium azide to prevent bacterial growth. Excellent selectivity enables AMP to be determined in serum. 

A final observation consistent with rate-determining cycli-zation is that the reaction rate is relatively insensitive to added electrolyte. Addition of 0.5 equivalents of tetra-n-butylammonium chloride or tetra-n-butylammonium azide to chloroform solutions of... 

Because aldrin contains the bicyclo-(2.2.1)-heptene ring structure, it reacts typically with phenyl azide to form a phenyldihydrotriazole derivative. This reaction is of importance in that it provides the basis for an analytical method for determining aldrin (discussed more fully in 2). 

A colorimetric procedure is described for the determination of small amounts of Compound 118 (1,2,3,4,10,10-hexa-chloro - 1,4,4a,5,8,8a - hexahydro - 1,4,.5,8 - dimethano-naphthalene). Reaction with phenyl azide to form a di-hydrotriazole derivative and subsequent treatment with diazotized dinitroaniline in strongly acid medium produce an intense red color. Amounts of the insect toxicant of 10 to 40 micrograms in the final 10-ml. aliquot are readily determined with a spectrophotometer. Commonly used insect toxicants do not interfere. 

Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of hydrogen sulfide in human whole blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. A detection limit of 4 g/dm3 and a percent recovery of 98-102% were achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. 

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