Ammonium irradiance effects

Since only absorbed light can initiate photo transformations, it may be expected that samples of different optical properties show different photoproduction rates. For comparative purposes, the rates are thus usually absorbance-normafized. However, the inconsistency when comparing results from different studies is not resolved by such normalization and the variabifity of normafized rates exceeds an order of magnitude (Table 10.1). An attempt to find a correlation between available bulk characteristics (DON, DOC, pH, absorbance) and irradiation effects proved unsuccessful (Grzybowski, 2003). Additional confusion is introduced by reports on lack of ammonium release and even its removal during irradiation, observed in apparently similar samples (Table 10.1). 

The electron spin resonance spectra were run in nitrogen-saturated solutions of aromatic compound ca. 10" m) and nucleophile (0-05-0-1 M) in the solvent(s) indicated. Irradiation in the cavity was effected with a high pressure mercury arc. Electrolysis was performed with the platinum cathode in the cavity, tetraethyl-ammonium perchlorate as electrolyte and electric currents of 10-250 /lA. 

Fig 25 The Effects of Gamma-Ray 235U Fission Spectrum Neutron, and Combined Gamma-Ray and Neutron Irradiation on Whole Crystals of Ammonium Perchlorate Thermally Decomposed at 227° (Ref 224)... 

Oxygen Taliani Test of Gamma-Irradiated Propellants ARP, AHH, and CDT , NPP-TMR-172, Naval Propint Plant, Indian Head (1959) 78) E.S. Freeman et al, The Effects of X-Ray and Gamma Ray Irradiation on the Thermal Decomposition of Ammonium Perchlorate in the Solid State , JPhysChem 64, 1727 (1960) also PATR 2673 (1960) 79) G. Todd E. Parry,... 

Centers in Ammonium Perchlorate by X-Ray Irradiation at Room Temperature , Radiation Effects 38, 231-38 (1978) 259) F.H. Mathews,... 

The Ni and Pt complexes can also be incorporated into polymer films of quaternized poly(vinylpyridine) (PVP) and deposited onto the transparent electrode (84). Photocurrents are enhanced to microamps (pA), an increase that may be attributed to either the effect of immobilization of the complexes near the electrode surface or an increase of the excited-state lifetimes in the polymer matrix. However, the effective concentrations of the complexes in this study were much greater than for the acetonitrile solutions in their earlier work. The polymer films are not stable to continuous photolysis, and voltammograms of the films are quite sensitive to anions used in the supporting electrolyte. The system can be stabilized by using a polymer blend of PVP and a copolymer containing quaternary ammonium ion and including [Fe(CN)6]4- in the electrolyte solution (85). Upon irradiation of the visible MLCT bands of [M(mnt)2]2 (M = Ni, Pt), photocurrents are produced. The mechanism (Scheme 4) is believed to involve photooxidation of the metal bis(dithiolene) triplet state by the Sn02 electrode, followed by [Fe(CN)6]4 reduction of the monoanion, with completion of the ET cycle as ferricyanide, Fe(CN)6 3, diffuses to the other electrode and is reduced. 

Table 9.13 summarizes the effect of the kind of reductant on the photochromic behavior of thionine dye. All reductants afforded transparent films upon irradiation and complete color recovery in the dark. The greatest photosensitivity was obtained with TEA as the reductant. The reversibility decreased in the order, tri->di->mono-ethanolamine. The difference cannot be explained by an electron-donating character such as the basicity of the reductant (P A a value of their ammonium salt tri-mono-ethanolamine). A potential explanation is that TEA(bp, 335.4°C/760mmHg) is so hygroscopic that the moisture absorbed in TEA and TEA itself acts as a plasticizer, providing tough films that afford higher color reversibility, as mentioned earlier. 

Kinetics in the irradiated system HI-NO have been studied by Holmes and Sundaram . They used 3130-3660 A radiation and a reaction cell temperature of 25 or 45 °C. Uranyl oxalate actinometry was employed. The photolysis of HI in this wavelength region produces hydrogen and iodine atoms which in turn react with either HI or NO. Holmes and Sundaram found that at 25 °C additions of NO significantly reduced the initial quantum yield of Hj. As the NO/HI ratio increased, the quantum yield fell to a limiting value. Additions of nitrogen to pure HI had no effect on the quantum yield. At 45 °C the reaction products were the same but the actinometry was irreproducible due to formation of ammonium iodide on the cell windows which reduced incident light intensities. 

The reaction between alkyl hahdes and ammonia or primary amines is not usually a feasible method for the preparation of primary or secondary amines, since they are stronger bases than ammonia and preferentially attack the substrate. However, the reaction is very useful for the preparation of tertiary amines and quaternary ammonium salts. If ammonia is the nucleophile, the three or four alkyl groups on the nitrogen of the product must be identical. If a primary, secondary, or tertiary amine is used, then different alkyl groups can be placed on the same nitrogen atom. The conversion of tertiary amines to quaternary salts is called the Menshutkin reaction It is sometimes possible to use this method for the preparation of a primary amine by the use of a large excess of ammonia or a secondary amine by the use of a large excess of primary amine. The use of ammonia in methanol with microwave irradiation has also been effective. Microwave irradiation has also been used in reactions of aniline with allyl iodides. A base other than the amine... 

Amino acids, nucleic acid bases and organic acids were synthesized by the UV irradiation of aqueous solutions in which CO2 and NH3 gases or ammonium carbonate had been dissolved. For the photosyntheses of amino acids and nucleic acid bases, the irradiation of UV hght of wavelengths shorter than 280 nm at temperatures higher than 80 °C and the coexistence of Mg " in the solution were foimd to be effective. Oxahc acid and/or oxamic acid were assiuned to be possible intermediates for the syntheses. 

In another experiment, an aqueous solution containing 10 % ammonium carbonate (pH = 8.9) was irradiated for 100 hrs at 90 °C. Concentrations of amino acids and nucleic add bases produced were similar to those observed with the (CO2 + NH3) solution as follows 1.7 X10 M glycine, 2.8 X10 M alanine, 6.0 X10 M serine, 1.4 X 10 M aspartic acid, 4.0X10" M cytosine and 1.8X10" M uracil. Effects of various conditions during irradiation were also similar to those with (CO2 + NH3) solutions, as summarized in Table 1. Therefore, subsequent experiments were carried out by using ammonium carbonate solutions instead of (CO2 + NH3) solutions. 

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