Copper Catalysed Oxygenation of Bis (2-pyridyl) methane and 6-Methyl-bis (2-pyridyl)methane to the Corresponding Ketones

The ligands (L) bis (2-pyridyl) methane (BPM) and 6-methyl-bis (2-pyridyl)methane (MBPM) form the three complexes CuL²⁺, CuL, and Cu₂L₂H with Cu²⁺. Stability constants are log K₁ = 6.23 ± 0.06, log K₂ = 4.83 ± 0.01, and log K (Cu₂L₂H + 2H²⁺ ? 2 CuL²⁺) = ?10.99 ± 0.03 for BPM and 4.56 ± 0.02, 2.64 ± 0.02, and ?11.17 ± 0.03 for MBPM, respectively. In the presence of catalytic amounts of Cu²⁺, the ligands are oxygenated to the corresponding ketones at room temperature and neutral pH. With BPM and 2,4,6-trimethylpyridine (TMP) as the substrate and the buffer base, respectively, the kinetics of the oxygenation can be described by the rate law with k₁ = (5.9 ± 0.2) · 10^?13 mol l^?1 s^?1, k₂ = (4.0 ± 0.6) · 10^?4 mol^?1 ls^?1, k₃ = (1.1 ± 0.1) · 10^?12 mol l^?1 s^?1, and k₄ = (9 ± 2) · 10^?14 mol l^?1 s^?1.     

Temperature and pressure effects on the kinetics of the Bromate ion-iodide ion-L-ascorbic acid clock reaction

The kinetics of the bromate ion-iodide ion-L-ascorbic acid clock reaction was investigated as a function of temperature and pressure using stopped-flow techniques. Kinetic results were obtained for the uncatalyzed as well as for the Mo(VI) and V(V) catalyzed reactions. While molybdenum catalyzes the BrO-I^? reaction, vanadium catalyzes the direct oxidation of ascorbic acid by bromate ion. The corresponding rate laws and kinetic parameters are as follows. Uncatalyzed reaction: r₂ = k₂[BrO] [I^?][H⁺]², k₂ = 38.6 ± 2.0 dm⁹ mol^?3 s^?1, ΔH? = 41.3 ± 4.2 kJmol^?1, ΔS? = ?75.9 ± 11.4 Jmol^?1 K^?1, ΔV? = ?14.2 ± 2.9 cm³ mol^?1. Molybdenum-catalyzed reaction: r′₂ = k₂[BrO] [I^?] [H⁺]² + k_Mo[BrO] [I^?] [ H⁺]²[M₀(VI)], k_Mo = (2.9 ± 0.3)10⁶ dm¹² mol^?4 s^?1, ΔH? = 27.2 ± 2.5 kJmol^?1, ΔS? = ?30.1 ± 4.5 Jmol^?1K^?1, ΔV? = 14.2 ± 2.1 cm³ mol^?1. Vanadium-catalyzed reaction: r′₁ = k_V[BrO] [V(V)], k_V = 9.1 ± 0.6 dm³ mol^?1 s^?1, ΔH? = 61.4 ± 5.4 kJmol^?1, ΔS? = ?20.7 ± 3.1 Jmol^?1K^?1, ΔV? = 5.2 ± 1.5 cm³ mol^?1. On the basis of the results, mechanistic details of the BrO-I^? reaction and the catalytic oxidation of ascorbic acid by BrO are elaborated. © 1995 John Wiley & Sons, Inc.     

Studies on the composition and kinetics of chromium(III)-alanine system

Kinetics of the complex formation of chromium(III) with alanine in aqueous medium has been studied at 45, 50, and 55°C, pH 3.3–4.4, and μ = 1 M (KNO₃). Under pseudo first-order conditions the observed rate constant (k_obs) was found to follow the rate equation: Values of the rate parameters (k_an, k, K_IP, and K) were calculated. Activation parameters for anation rate constants, ΔH^≠(k_an) = 25 ± 1 kJ mol^?1, ΔH^≠(k) = 91 ± 3 kJ mol^?1, and ΔS^≠(k_an) = ?244 ± 3 JK^?1 mol^?1, ΔS^≠(k) = ?30 ± 10 JK^?1 mol^?1 are indicative of an (I_a) mechanism for k_an and (I_d) mechanism for k routes (‥substrate Cr(H₂O) is involved in the k route whereas Cr(H₂O)₅OH²⁺ is involved in k′ route). Thermodynamic parameters for ion-pair formation constants are found to be ΔH°(K_IP) = 12 ± 1 kJ mol^?1, ΔH°(K) = ?13 ± 3 kJ mol^?1 and ΔS°(K_IP) = 47 ± 2 JK^?1 mol^?1, and ΔS°(K) = 20 ± 9 JK^?1 mol^?1.     

Variable-Temperature and Variable-Pressure Kinetic and Equilibrium studies of formation and dissociation of [V(H2O)5NCS]2+

The kinetics of formation and dissociation of [V(H₂O)₅NCS]²⁺ have been studied, as a function of excess metal-ion concentration, temperature, and pressure, by the stopped-flow technique. The thermodynamic stability of the complex was also determined spectrophotometrically. The kinetic and equilibrium data were submitted to a combined analysis. The rate constants and activation parameters for the formation (f) and dissociation (r) of the complex are: k/M ^?1 · S^?1 = 126.4, k/s^?1 = 0.82; ΔH /kJ · mol^?1 = 49.1, ΔH/kJ · mol^?1 = 60.6; ΔS/ J·K^?1·mol^?1= ?39.8, ΔSJ·K^?1·mol^?1 = ?43.4; ΔV/cm³·mol^?1 = ?9.4, and ΔV/cm³ · mol^?1 =?17.9. The equilibrium constant for the formation of the monoisothiocynato complex is K²⁹⁸/M ^?1 = 152.9, and the enthalpy and entropy of reaction are ΔH⁰/kJ · mol^?1 = ? 11.4 and ΔS⁰/J. K^?1mol^?1 = +3.6. The reaction volume is ΔV⁰/cm³· mol^?1 = +8.5. The activation parameters for the complex-formation step are similar to those for the water exchange on [V(H₂O)₆]³⁺ obtained previously by NMR techniques. The activation volumes for the two processes are consistent with an associative interchange, I_a, mechanism.     

Laser-induced kinetics: Arrhenius parameters for t-C4H9 + XI → i-C4H9X + I (X = H,D) and the Heat of Formation of the t-butyl radical

The metathesis reaction of DI with t-C₄H₉ generated by 351-nm photolysis of 2,2′-azoisopropane was studied in a low-pressure reactor (VLP? Knudsen cell) in the temperature range of 302–411 K. The data obeyed the following Arrhenius relation when combined with recent data by Rossi and Golden gathered by the same technique (t-C₄H₉ by thermal decomposition of 2,2′-azoisobutane): log k₂^D(M^?1s^?1) = 9.60 – 1.90/θ, where θ = 2.303RT kcal/mol for 302 K < T > 722 K. The metathesis reaction of HI with t-C₄H₉ was studied at 301 K and resulted in k₂^H(M^?1·s^?1) = (3.20 ± 0.62) × 10⁸. An analogous Arrhenius relation was calculated for the protiated system if the small primary isotope effect k₂^H/k₂^D was assumed to be √2 at 700 K. It was of the following form: log k₂^H(M^?1·s^?1) = 9.73 – 1.68/θ. Preliminary data of Bracey and Walsh indicate that earlier Arrhenius parameters determined for the reverse reaction are somewhat in error. Their value of log k₁(M^?1·s^?1) = 11.5 – 23.8/θ yields 7delta;H_f,300⁰(t-butyl) = 9.2 kcal/mol and S₃₀₀⁰(t-butyl) = 74.2 cal/mol7°K when taken in conjuction with this study.     

The azoethane-initiated thermal reaction of isobutene. Heat of formation of the 2-methyl-2-pentyl radical

The azoethane-sensitized thermal reaction of isobutene has been studied at 526–565 K. The initial concentrations of azoethane and isobutene were in the ranges of 1.40–10.5 × 10^?4 and 6.78–26.6 × 10^?4 mol/dm³, respectively. From the initial rates of formation of ethane and 2-methylpentane the heat of formation of the 2-methyl-2-pentyl radical was determined. The result obtained is ±H(2-methyl-2-pentyl) = 0.8 ± 2.0 kcal/mol. The entropy of the radical, obtained from statistical mechanical calculations and experimentally, is S⁰(2-methyl-2 pentyl) = 92.8 ± 1.5 cal/mol°K. The results support the high heat of formation of the t-butyl radical suggested by different authors.     

Kinetic studies of the reactions CH2I2 + HI⇄CH3I + I2 and 2 CH3I⇄CH4 + CH2I2 the heat of formation of the iodomethyl radical

The rate of the reaction CH₂I₂ + HI ? CH₃I + I₂ has been followed spectrophotometrically from 201.0 to 311.2°. The rate constant for the reaction fits the equation, log (k₁/M^?1 sec^?1) = 11.45 ± 0.18 - (15.11 ± 0.44)/θ. This value, combined with the assumption that E₂ = 0 ± 1 kcal/mole, leads to ΔH (CH₂I, g) = 55.0 ± 1.6 kcal/mole and DH (H? CH₂I) = 103.8 ± 1.6 kcal/mole. The kinetics of the disproportionation, 2 CH₃I ? CH₄ + CH₂I₂ were studied at 331° and are compatible with the above values.     

Ab initio calculation of electronic states of the ions H4+ and H5+

Electronic state calculations for the ions H₄⁺ (with symmetries D ₄ and C _2v) and H (with symmetries D ₅ and D _2d) are made using the valence-bond method. All the configurations obtained from the given set of 1s-functions of Slater type are taken into account. Space functions are used throughout the computation (“spin-free quantum chemistry”). Preliminary quasidiagonalization of the secular equation is implemented by the construction of the multiplet eigenfunctions ^2S+1Γ^(α) from the initial variational functions. The results of the calculations are as follows: the ion H is unstable, the ion H is stable with equilibrium nuclear conformation of symmetry D _2d and with the energy of dissociation into H and H₂ near 4 eV.     

Kinetic study of the reactions of CL and BR with H2O2

The reactions of Cl and Br atoms with H₂O₂ have been studied in the range of 300–350 K using the very-low-pressure-reactor technique. It was found that metathesis to produce HX and HO₂ is the only significant process (≤99%). For the reaction of Br k₂ (300 K) = 1.3 ± 0.45 × 10^?14 and k₂ (350 K) = 3.75 ± 1.1 × 10^?14 cm³/molecules·s, with an activation energy of 4.6 ± 0.7 kcal/mol. Using an estimated A factor for A₂, we find suggesting that a best choice is E₂ = 3.9 ± 0.4 kcal/mol. The relation of these values to ΔH (HO₂) is discussed.     

On the mechanism of the Hg2+ and base induced hydrolysis reactions of the β2-(RR,SS)-Co (trien) (glyOR)Cl2+ions (R = H,C2H5), evidence for the site of deprotonation in the reactive conjugate base

Acid hydrolysis of the ester function in Δ-(?)₅₈₉-β₂-(RR)-[Co (trien) (glyOEt) Cl]²⁺ ((?)- 1 ) produces optically pure Δ-(?)₅₈₉-(RR)-[Co (trien) (glyOH)Cl]²⁺ ((?)- 4 ). Hg²⁺ induced removal of chloride in (?)- 4 follows the rate law k_obs = k_Hg [Hg²⁺] with k_Hg = (1.36 ± 0.03) × 10^?2 M^?1s^?1, 25°, μ=1.0, and produces optically pure Δ-(?)₅₈₉-β₂-(RR)-[Co(trien) (glyO)]²⁺ ((?)- 2 ). Competition by NO occurs in this reaction ([NO], 1M, 3%) indicating a path whereby external nucleophiles (Y?NO, H₂O) compete with the intramolecular carboxylate function for an intermediate of reduced coordination number. Rapid ring closure to 2 must ensue for Y ? H₂O. Base hydrolysis of chloride in (±)- 1 produces (±)- 2 together with its diastereoisomer β₂-(RS, SR)-[Co(trien) (glyO)]²⁺, ((±)- 3 ), in which one secondary amine function has an inverted configuration. 2 and 3 incorporate ¹⁸O-labelled solvent into the Co-O position of the coordinated carboxylate moiety ( 2: 9.0%; 3: 12.3%) indicating that at least part of the product arises via intramolecular hydrolysis in β₂-hydroxo ethylglycinate intermediates (Fig. 4). Base hydrolysis of (?)- 4 follows the rate law K_obs = k_OH[OH^?] with k_OH = (6.3 ± 0.6) × 10^?4M^?1 S^?1, 25°, μ = 1.0 producing (?)- 2 (37-45%) and (?)- 3 (63-55%), the ratio being somewhat medium dependent. Competition by added N (1M) occurs using (±) - 4 forming β₂-(RR, SS)-[Co (trien) (glyO)N₃]⁺ (～2%) and β₂-(RS, SR)-[Co (trien) (glyO)N₃]⁺ (～ 13%). Mutarotation at the secondary nitrogen centre is shown to occur after the rate determining loss of Cl^? in 1 and 4 and before the formation of 2 and 3 . It is concluded that this secondary nitrogen is the site of deprotonation in the reactive conjugate bases of 1 and 4 , and possible mechanisms for the mutarotation process are considered.     

Analysis of the kinetics of the thermal and chemically activated elimination of HF from 1,1,1-trifluoroethane: the C?C bond dissociation energy and the heat of formation of 1,1,1-trifluoroethane

The thermal, unimolecular elimination of HF from CH₃CF₃ was studied by three different groups over the temperature range 1000° to 1800°K. While the reported kinetic parameters varied greatly, it is shown here that these data may be satisfactorily correlated in terms of a four-center transition state. This correlation results in ΔE = 69.2 kcal/mol, and log (k/s^?1) = 14.6 – 72.6/θ. These results may then be combined with the kinetics of the chemically activated elimination of HF from CH₃CF₃ formed by the recombination of methyl and trifluoromethyl radicals. The data from three different laboratories are shown to be in excellent agreement. These data, combined with extant thermal data, yield as a best value DH(CH₃? CF₃) = 99.6 ± 1.1 kcal/mol. This gives the unexpectedly high value of DH₂₉₈°(CH₃? CF₃) = 101.2 ± 1.1 kcal/mol. It is suggested that dipoledipole interactions, primarily in CH₃CF₃, account for this surprisingly strong C? C bond dissociation energy. These results also yield δH(CH₃CF₃; g, 298) = ?178.6 ± 1.5 kcal/mol.     

Iodine catalyzed pyrolysis of dimethyl sulfide. Heats of formation of CH3SCH2I,the CH3SCH2 radical,and the pibond energy in CH2S

A kinetic study has been made of the gas phase, I₂-catalyzed decomposition of (CH₃)₂S at 630–650 K. Some I₂ is consumed initially, reaching a steady-state concentration. The initial major products are CH₄ and CH₂S together with small amounts of CH₃SCH₂I, CH₃I, HI, and CS₂. The initial reaction corresponds to a pseudo-equilibrium: accompanied by: and which brings (I₂) into steady state and a final complex reaction: From the initial rate of I₂ loss it is possible to obtain Arrhenius parameters for the iodination: We measure k₁, (644 K) = 150 L/mol s and from both the Arrhenius plot and independent estimates A₁ (644 K) = 10^{11.2 ± 0.3} L/mol s. Thus, E₁ = 26.7 ± 1 kcal/mol. From the steady-state I₂ concentration, an assumed mechanism and the known rate parameters for the CH₃I/HI system. It is possible to deduce K_A (644) = 3.8 × 10^?2 with an uncertainty of a factor of 2. Using an estimated ΔS (644) = 4.2 ± 1.0 e.u. we find ΔH_A (644) = 7.0 ± 1.1 kcal. With 〈ΔC_PA〉644 = 1.2 this becomes: ΔH_A(298) = 6.6 ± 1.1 kcal/mol. Then ΔH (CH₃SCH₂I) = 6.3 ± 1 kcal/mol. Making the assumption that E_?1 = 1.0 ± 0.5 kcal/mol we find ΔH (644) = 25.7 ± 0.7 kcal/mol and with 〈ΔC_PI〉 = 1.2; ΔH = 25.3 ± 0.8 kcal/mol. This gives ΔH (CH₃S?H₂) = 35.6 ± 1.0 kcal/mol and DH (CH₃SCH₂? H) = 96.6 ± 1.0 kcal/mol. This then yields E_π(CH₂S) = 52 ± 3 kcal. From the observed rate of pressure increase in the system and the preceding data k₃, is calculated for the step CH₃SCH₂ → CH₃ + CH₂S. From an estimated A-factor E₃ is deduced and from the overall thermochemistry values for k_?3 and E_?3. A detailed mechanism is proposed for the I-atom catalyzed conversion of CH₂S to CS₂ + CH₄.     

Kinetic study of the gas-phase reaction c-C5H10 + I2 ⇄ c-C5H8 + 2HI the heat of formation of cyclopentyl radical

The kinetics of the gas-phase dehydrogenation of cyclopentane to cyclopentene is found to be consistent with a slow attack by an I atom (step 4, text) on cyclopentane in the range 282–382°C. The measured rate constants fit the Arrhenius equation, log k₄ = 11.95 ± 0.08 – (24.9 ± 0.23)/θ 1 mole^?1 sec^?1, where θ = 2.303 R T in kcal/mole. This leads to a value of ΔH = 24.3 ± 1 kcal/mole and a bond dissociation energy DH = 94.9 ± 1 kcal/mole. The latter value is identical with DH⁰(i-Pr-H) = 95 ± 1 kcal/mole and signifies that cyclopentane and the cyclopentyl radical have the same strain energy. Arrhenius parameters are deduced for all six steps in the reaction mechanism. Surface reactions are shown to be unimportant. Cyclopentyl iodide is an unstable intermediate in the reaction and the rate constant for its bimolecular formation from HI + cyclopentene is found to be log k₆ = 8.40 ± 0.29 - (26.9 ± 0.8)/θ 1 mole^?1 sec^?1. Together with the equilibrium constant, this yields for the unimolecular elimination of HI from cyclopentyl iodide, the rate constant, log k₅ = 13.3 ± 0.3 – (42.8 ± 1.2)/θ sec^?1.     

Stability of Complex Metal Bromides in the gas phase and in toluene

The equilibrium constants of the reactions MBr₂(s) + Al₂Br₆(sln) ? MAl₂Br₈(sln) M = Cr, Mn, Co, Ni, Zn, Cd have been measured at 298 K in toluene. Ni: 0.017 ± 0.0024, Co: 0.54 ± 0.07, Zn: 1.5 ± 0.2, Mn: 2.1 ± 0, 7, Cr: 2.2 ± 1, Cd: 7 ± 5. They are compared with literature values of the equilibrium constants of analogous reactions in the gas phase MX₂(s) + Al₂X₆(g) ? MAl₂X₈(g), X = Cl, Br. For CoAl₂Br₈(sln) the temperature dependence of the equilibrium constant yielded Δ_fH = ?9.4 ± 1 kJ mol^?1 and Δ_fS = ?39.5 ± 3 J mol^?1 K^?1 while literature values for CoAl₂Br₈(g) are Δ_fH = 42.4 ± 2 kJ mol^?1 and Δ_fS = 42.9 ± 2 J mol^?1 K^?1. The solubility of Al₂Br₆ in toluene as well as its enthalpy of dissolution have been measured in order to evaluate ΔH° and ΔS° of the solvation of Al₂Br₆(g) and CoAl₂Br₈(g) in toluene by a thermodynamic cycle. Solvation of Al₂Br₆(g): ΔH = ?72.7 ± 1 kJ mol^?1, ΔS = ?139.6 ± 4 J mol^?1 K^?1, solvation of CoAl₂Br₈(g): ΔH = ?124.5 ± 4kJ mol^?1, ΔS = ?222 ± 9J mol^?1 K^?1. Thus, CoAl₂Br₈ interacts more strongly with the solvent toluene than Al₂Br₆ does.     

Kinetic study of reactions of C2H5O2 with NO at 298 K and 0.55 – 2 torr

The kinetics of C₂H₅O₂ and C₂H₅O₂ radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C₂H₅O were monitored by LIF. The rate constant for C₂H₅O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k₂ = (1.25±0.04) × 10^?11, (1.66±0.06) × 10^?11, (1.81±0.06) × 10^?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm³ molecule^?1 s^?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C₂H₅O + NO + M → C₂H₅ONO + M (2a), C₂H₅O + NO → CH₃CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k_2a and for k_2b : k = (2.6±1.0) × 10^?28 cm⁶ molecule^?2 s^?1, k = (3.1±0.8) × 10^?11 cm³ molecule^?1 s^?1 and k_2b ca. 8 × 10^?12 cm³ molecule^?1 s^?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10^?27 cm⁶ molecule^?2 s^?1 recommended in air. The rate constant for the reaction C₂H₅O₂ + NO → C₂H₅O + NO₂ (3) has been measured at 1 torr of He from the simulation of experimental C₂H₅O profiles. The value obtained for k₃ = (8.2±1.6) × 10^?12 cm³ molecule^?1 s^?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc.     

Kinetic Studies on the Reaction of Sodium Hexacyanoferrate（ll） Complex with Peroxydisulfate Anion

The oxidation of Na₄Fe(CN)₆ complex by S₂O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k_ox, are (8.1±0.07)×10^?2 and (4.3±0.1)×10^?2 mol^?1·L·s^?1 at μ=1.0 mol·L^?1 NaClO₄, T=298 K for pH=1 (0.1 mol·L^?1 HCl0₄) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH^≠=(69.0±5.6) kJ·mol^?1, ΔS^≠=(?0.34±0.041)×10² J·mol^?1·K^?1 at pH=l and ΔH^≠=(41.3±5.5) kJ·mol^?1, ΔS^≠=(?1.27±0.33)×10² J·mol^?1·K^?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E_1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L^?1 LiClO₄, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.     

Zur Kristallstruktur von SrZn(OH)4 · H2O

Crystal Structure of SrZn(OH)₄ · H₂O Colorless crystals of SrZn(OH)₄ · H₂O are obtained by electrochemical oxidation of Zn in a zinc/iron pair in an aqueous ammonia solution saturated with strontium hydroxide. The X-ray crystal structure determination was now successful including all hydrogen positions: P1 , Z = 2, a = 6.244(1) Å, b = 6.3000(8) Å, c = 7.701(1) Å, α = 90.59(1)°, β = 112.56(2)°, γ = 108.66(2)°, N(F ≥ 3σF) = 1967, N(Var.) = 84, R/R_w = 0.020/0.024. In SrZn(OH)₄ · H₂O Zn²⁺ is tetrahedrally coordinated by four OH^? -ions while Sr²⁺ has 6 OH^? and one H₂O as neighbours. The polyhedra around Sr²⁺ are connected to chains which are linked three-dimensionally by isolated tetrahedra [Zn(OH)₄]. Hydrogen bonds between H₂O as donor and OH^? are characterized by raman spectroscopy.     

The heats of formation of NO3− and NO3− association complexes with HNO3 and HBr

The equilibrium constant for the reaction has been determined between 331 and 480°K using a variable-temperature flowing afterglow. These data give ΔH°(1) = -1.03 ± 0.21 kcal/mol and ΔS°(1) = —4.6 ± 1.0 cal/mol°K. When combined with the known thermochemical values for HBr, Br^?, and HNO₃, this yields ΔH(NO₃^?) = -74.81 ± 0.54 kcal/mol and S(NO₃^?) = 59.4 cal/mol·°K. In addition ΔH_n-1,n and ΔS_n-1,nfor the gas-phase reactions were determined for n = 2 and 3. The implications of these measurements to gas-phase negative ion chemistry are discussed.     

Crystal Structures of {[Cd(phen)](C6H8O4)3/3} and {[Cd(phen)](C7H10O4)3/3} · 2H2O with C6H10O4 = Adipic Acid and C7H12O4 = Pimelic Acid

Two coordination polymers {[Cd(phen)](C₆H₈O₄)_3/3} ( 1 ) and {[Cd(phen)](C₇H₁₀O₄)_3/3} · 2H₂O ( 2 ) were structurally characterized by single crystal X‐ray diffraction methods. In 1 (C2/c (no. 15), a = 16.169(2)Å, b = 15.485(2)Å, c = 14.044(2)Å, β = 112.701(8)°, U = 3243.9(7)ų, Z = 8), the Cd atoms are coordinated by two N atoms of one phen ligand and five O atoms of three adipato ligands to form mono‐capped trigonal prisms with d(Cd‐O) = 2.271‐2.583Å and d(Cd‐N) = 2.309, 2.390Å. The [Cd(phen)] moieties are bridged by adipato ligands to generate {[Cd(phen)](C₆H₈O₄)_3/3} chains, which, via interchain π—π stacking interactions, are assembled into layers. Complex 2 (P1¯(no. 2), a = 9.986(1)Å, b = 10.230(3)Å, c = 11.243(1)Å, α = 66.06(1)°, β = 87.20(1)°, γ = 66.71(1)°, U = 955.7(2)ų, Z = 2) consists of {[Cd(phen)](C₇H₁₀O₄)_3/3} chains and hydrogen bonded H₂O molecules. The Cd atoms are pentagonal bipyramidally coordinated by two N atoms of one phen ligand and five O atoms of three pimelato ligands with d(Cd‐O) = 2.213—2.721Å and d(Cd‐N) = 2.329, 2.372Å. Through interchain π—π stacking interactions, the {[Cd(phen)](C₇H₁₀O₄)_3/3} chains resulting from [Cd(phen)] moieties bridged by pimelato ligands are assembled in to layers, between which the hydrogen bonded H₂O molecules are sandwiched.     

Some thermodynamic parameters for hydroxy amino acids: Bicine and tricine

pK values of N,N-dihydroxyethylglycine (bicine) and N-[tris(hydroxymethyl)methyl]-glycine (tricine) have been determined by the Irving-Rossotti method in an aqueous medium at 25, 30, 35, 40, 45, and 50°C and at different ionic strengths (I = 0.1, 0.5, and 1.0). Plots between pK_a(NH) and 1/T for various ionic strengths have been obtained and the values of slopes have been used to calculate the ΔH, ΔS, and ΔG for the dissociation reactions of bicine and tricine. The ΔH, ΔS, and ΔG values for bicine were found to be 10.6 ± 0.6 kcal mol^?1, ?1.9 ± 1.8 e.u., and 11.1 ± 0.06 kcal mol^?1, respectively, and for tricine 11.2 ± 0.6 kcal mol^?1, 1.6 ± 1.6 e.u., and 10.7 ± 0.06 kcal mol^?1, respectively. The pK_a(NH) values decrease with rise in temperature but the influence of ionic strength is not significant.