硝酸及其氧化性问题的探讨

硝酸是常见的无机酸之一，它的化学性质除表现为强酸外，主要特征是氧化性。由于其还原产物随本身浓度、还原剂的活泼性和温度因素而变，因此它们之间的反应过程很复杂[1]。目前所见的无机教材一般只用氧化还原电位来解释HNO3氧化性，并未讨论它的反应机理。本文试用氧化还原电位和反应速率及反应机理等方面进行讨论，以便更好解释其氧化性和还原产物。

Theoretical Study on Dissociation Potential Energy Surface of Peroxynitric Acid

The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.

Effects of N Forms and Rates on Vegetable Growth and Nitrate Accumulation

Experiments were carried out on a vegetable field with Peking cabbage(Brassica pekinensis (Lour.) Rupr.), cabbage (Brassica, chinensis var. oleifcra Makino and nemoto),green cabbage (Brassica chinensis L.), spinach (Spinacia oleracea L.) and rape(Brassica campestrisL.) to study the effects of N forms and N rates on their growth and nitrate accumulation. Theresults indicated that application of ammonium chloride, ammonium nitrate, sodium nitrate and ureasignificantly increased the yields and nitrate concentrations of Peking cabbage and spinach.Although no significant difference was found in the yields after application of the 4 N forms,nitrate N increased nitrate accumulation in vegetables much more than ammonium N. The vegetableyields were not increased continuously with N rate increase, and oversupply of N reduced the plantgrowth, leading to a yield decline. This trend was also true for nitrate concentrations in somevegetables and at some sampling times. However, as a whole, the nitrate concentrations in vegetableswere positively correlated with N rates. Thus, addition of N fertilizer to soil was the major causefor increases in nitrate concentrations in vegetables. Nitrate concentrations were much higher inroots, stems and petioles than in blades at any N rate.

Crystal Structure of[La(NO_3)_3(12-crown-4)-(H_2O)](12-crown-4)

The crystal structure of crown ether-hydrogen bonded complex,[La(NO3)3 (12-crown-4) ( H2O)] (12-crown-4) has been determined by X-ray method. The title complex C16H34LaN3O18 (Mr=695. 5) crystallized in orthorhombic Pnma with a=23. 495(8), b=13. 603(5),c=8. 474(3); V=2706(1); Z=4 ; Dc=1. 71 g/cm3; F(000)=1408, μ=17. 0 cm-1 (MOKα). The final R=0. 052 and Rw= 0. 054(unit weight) for 1367 observed reflections. The La( Ⅲ) ion is 11-coordinated by three nitrale anions, four oxygen atoms from a crown ligand and one O atom of a water molecule. The other crown molecule is hydrogen bonded wilh the coordinated water molecule. The imposed mirror plane in the structure made both crown ligands and one of nitrate groups severely disordered.

Crystal Structures of Ln(NO_3)_3(Ln=La,Yb) Complexes with 12-crown-4

The synthesis and crystal structures of Ln(NO3)3(Ln=La,Yb) complexes with 12-crown-4 are reported. La (NO3 )3 (12-crown-4) (H2O)x(Ln=La,x=1; Ln=Yb, x=0), Mr=519. 2(535.3), space group P21/n(P21/c)with α =7. 612(2)(12. 116(3)), b=13. 932(6) (8. 544(3)),c= 16. 179(6) (15.241 (3));β=101.40 (2)( 91.82 (2))°; V=1682 (1) (1577(1)); Z=4 (4);μ(MoKα)=26.7(63.2) cm -1; F(000) =1024 (1036) ; R=0. 035 (0. 034) ; Rw= 0. 028 (0.036) for 1665 (1594) observed reflections with Ⅰ>3σ(Ⅰ). The La(Ⅲ) ion in La (NO3)3 (12-crown-4) (H2O) is 11-coordinated, being bonded to three bidentate nitrate ions , four oxygen atoms of the crown molecule and one oxygen atom of a water molecule. Yb(NO3)3 (12-crown-4) is a 10-coordinated complex, in which the metal ion bonds with three bidentate nitrate ions and four oxygen atoms of a crown ether.

Preparation and Crystal Structure of Sarcosine 5-Nitrosalicylic Acid Organic Adduct

The title compound (C10H12N2O7, Mr = 272.22) crystallizes in triclinic, space group P1 with a = 5.532(2), b = 9.760(4), c = 11.731(5) ?, α = 68.107(7), β = 89.179(7), γ = 77.830(7)o, V = 573.1(4) ?3, Z = 2, Dc = 1.578 g/cm3, F(000) = 284 and μ(MoKa) = 0.136 mm-1. The final R = 0.0400 and wR = 0.0951 for 1468 observed reflections with I > 2σ(I). The title compound is a 1:1 adduct of sarcosine and 5-nitrosalicylic acid. The nitrogen atom of sarcosine is protonated, and the proton is from the carboxyl group of sarcosine and 5-nitrosalicylic acid with the probability of 50 percent for each. The 5-nitrosalicylic acid and sarcosine molecule of the title adduct are ABAB arranged along the c axis. There exist a lot of hydrogen bonds in the structure, linking sarcosine and 5-nitrosalicylic acid to form a three-dimensional network.

Synthesis and Crystal Structure ofDinitratedioxobis(p-methyl Phenyl Butyl Sulfoxide)Uranium(Ⅵ)[UO_2(p-CH_3C_6H_4SOC_4H_9)_2(NO_3)_2]

The title compound [UO2 （p-CH3C6H4SOC4H9）2 （NO3 ）2] is triclinicwith space group P1. a=8. 651 （3）, b=9. 097（2）, c=9. 621 （2） A;a=92. 29（1）, β=95. 97（3）, r=98. 25（3）, V=744. 1（3） A3, Z=1, Mr=786.41, Dc=1. 425 g/cm3. u=5. 626 mm-1, F （000） =300. R=0. 030, Rw=0. 071 for 2917 reflectionswith I≥2（I）. Uranyl ion is coordinated to six oxygen atoms, of which two are fromtwo monodenate sulfoxides and the others from two nitrate groups. The coordinationPOlyhedron around U is a hexagonal bipyramid, the U atom is in the center of symmetry.

Crystal Structure of Trinitratotri(Butylcaprolactam) Terbium(Ⅲ) Tb[■C_4H_9]_3(NO_3)_3

Tb[CH_2(CH_2)_4CONC_4H_9]_3(NO_3)_3,Mr=821.92. It is monoclinic,space group P2_1/c,a=18.604(2), b=9.768(1),c=21.887(3),β=96. 06(1)°,V=3955. 4(8),Z=4,Dc=1.43 g/cm￣3, MoKα radiation,μ=23.19 cm-1,F(000)=1760, R=0.039 for 2982 reflections with I>3σ(I).Tb(Ⅲ) is coordinated by three carbonyls of the three organic ligands and three bidentate nitrate groups. So each Tb(Ⅲ) is coordinated by nine oxygen atoms to form a distorted tricapped trigonal prism.