A microwave and quantum chemical study of the conformational properties and intramolecular hydrogen bonding of 1-fluorocyclopropanecarboxylic acid

The structural and conformational properties of 1-fluorocyclopropanecarboxylic acid have been explored by microwave spectroscopy and a series of ab initio (MP2/6-311++G(d,p) level), density functional theory (B3LYP/aug-cc-pVTZ level), and G3 quantum chemical calculations. Four "stable" conformers, denoted conformers I-IV, were found in the quantum chemical calculations, three of which (conformers I -III) were predicted to be low-energy forms. Conformer I was in all the quantum chemical calculations predicted to have the lowest energy, conformer III to have the second lowest energy, and conformer II to have the third lowest energy. Conformers II and III were calculated to have relatively large dipole moments, while conformer I was predicted to have a small dipole moment. The microwave spectrum was investigated in the 18-62 GHz spectral range. The microwave spectra of conformers II and III were assigned. Conformer I was not assigned presumably because its dipole moment is comparatively small. Conformer II is stabilized by an intramolecular hydrogen bond formed between the fluorine atom and the hydrogen atom of the carboxylic acid group. Conformer III has a synperiplanar orientation for the F-C-C=O and H-O-C=O chains of atoms. Its dipole moment is: mua = 3.4(10), mub = 10.1(13), and muc = 0.0 (assumed) and mu(tot) = 10.6(14) x 10(-30) C m [3.2(4) D]. Several vibrationally excited states of the lowest torsional mode of each of II and III were also assigned. The hydrogen-bonded conformer II was found to be 2.7(2) kJ/mol less stable than III by relative intensity measurements. Absolute intensity measurements were used to show that the unassigned conformer I is the most abundant form present at a concentration of roughly 65% at room temperature. Conformer I was estimated to be ca. 5.0 kJ/mol more stable than the hydrogen-bonded rotamer (conformer II) and ca. 2.3 kJ/mol more stable than conformer III. The best agreement with the theoretical calculations is found in the MP2 calculations, which predict conformer I to be 5.1 kJ/mol more stable than III and 1.7 kJ/mol more stable than II.     

Intramolecular hydrogen bonding in some acyclic alcohols

The extent of intramolecular hydrogen bonding, occurring in dilute CCl₄ solutions, of members of the series (n = 2–5) HO.(CH₂)_n.OH and MeO.(CH₂)_n.OH has been determined. The results permit the interpretation of the patterns of hydrogen bonding in the three monomethyl ethers of butane-1,2,4-triol and in 1,4-dimethoxybutan-2-ol. In these compounds, where hydrogen bonding allows the formation of rings of different sizes the sequence of preference 5> 6> 7 was observed.     

Ab initio study of anomeric effect in 2,2-difluoroglycine

The optimized molecular structures of seven conformations of 2,2-difluoroglycine have been obtained from ab initio calculations. For conformers in which the lone pair of electrons on the nitrogen are antiperiplanar to one of the C–F bonds, that C–F bond is longer than the other C–F bond, which is synperiplanar to the lone pair of electrons. Conformers which have these features are the most stable conformers of those examined. This observation is explained in terms of an anomeric effect of the 1p(N)→σ^*(C–F). At the MP2/6-31G^* level of calculation, conformers IV and V are 21.5 and 18.7 kJ/mol, respectively, more stable than the least stable conformer, VI, which does not exhibit an anomeric effect. Conformer VII was found to be exceptionally stable, in addition to an anomeric effect, this conformer also exhibits features of a FH–O hydrogen bond.     

Prediction of geometries and interaction energies of complexes formed by small molecules using semiempirical and ab initio methods

The accuracy of the semiempirical quantum mechanics methods (AM1 and PM3), and the ab initio methods (6-31G^** and MP2/6-31G^**) in predicting intermolecular geometries and interaction energies have been evaluated by detailed studies of 17 bimolecular complexes formed by small molecules. Comparisons between calculated and experimental geometries for 12 complexes are presented. It was found that AM1 gave reasonably good predictions of the geometries of complexes such as CH₄ · CH₄, which have very weak interactions, but it is not as good as other methods in predicting intermolecular geometry for complexes where hydrogen bonding interactions play an important role. This is consistent with its inability to reproduce the charge transfer in the formation of hydrogen bonds in these complexes.

PM3 is able to predict intermolecular geometries for most complexes, including those with hydrogen bonding; its major flaw is its tendency to overestimate the strength of the interactions between hydrogen atoms. Care should be taken therefore in using PM3 to study complicated molecular systems with multiple hydrogen atom interactions and the method's weakness in handling complexes in which electrostatic forces are important should also be noted.

Among ab initio methods, both the 6-31G^** and the MP2/6-31G^** were found to outperform AM1 and PM3 in prediction of intermolecular geometry. Both of these ab initio methods showed excellent consistency in geometry prediction for most of the complexes studied, although MP2/6-31G^** is better than 6-31G^**. It is noted that the MP2/6-31G^** did not produce the correct geometry for the CO₂· HF complex.

For 12 complexes for which experimental geometry data are available, AM1, PM3, 6-31G^**, and MP2/6-31G^** successfully predicted the geometry in 10, 12, 12, and 11 cases, respectively. The average errors given by AM1 in the predicted intermolecular distances were 0.264, 0.272, 0.091, and 0.061 Å, respectively. In comparison to the ab initio methods, AM1 and PM3 commonly underestimated the molecular interaction energy in such complexes by ˜ 1–2 kcal mol⁻¹.     

Enantioselective organic syntheses using chiral transition metal complexes V. (2S,3S)-Bis(dibenzophospholyl)butane, a rigid (S,S)-CHIRAPHOS analog

The P–Ph cleavage of phenyldibenzophosphole (1) with lithium in THF gives lithium dibenzophospholide (2). Reaction of 2 with ethyleneglycol ditosylate produces the known chelate ligand 1,2-bis(dibenzophospholyl)ethane (3) in good yield. Similarly, 2 and (2R,3R)-butanediol ditosylate give the new chiral chelate ligand (2S,3S)-bis(dibenzophospholyl)butane (4). Ligand exchange of [CpRu(PPh₃)₂Cl] with 3 or 4 yields the halfsandwich complexes [CpRu(C₁₂H₈PC₂H₄PC₁₂H₈)Cl] (5) and [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)Cl] (6). Complex 6 was characterized crystallographically (monoclinic, space group P2₁ (no. 4), a=820.6(4), b=1501.0(3), c=1172.8(6) pm, β=108.87(2)°, V=1.367(1)×10⁹ pm³, Z=2). The most conspicuous feature of the structure of 6 is the perfect coplanarity of the two dibenzophosphole moieties imposed by their steric interaction with the Cp ligand. Complex 6 and the thiophene complex [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)(SC₄H₄)]BF₄ (7) derived therefrom are remarkably unreactive with regard to ligand substitutions. A possible explanation is the lack of intramolecular

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–C stabilization en route to the transition state of ligand substitution. The enantiomeric purity of 6 and 7 could nevertheless be demonstrated by conversion to diastereomerically pure [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)((S)-CNCHMePh)]BF₄ (8).     

1,3-Diaxial steric effects and intramolecular hydrogen bonding in the conformational equilibria of new cis-1,3-disubstituted cyclohexanes using low temperature NMR spectra and theoretical calculations

The conformational equilibria of 3-X-cyclohexanol [X=F (1), Cl (2), Br (3), I (4), Me (5), NMe(2) (6) and MeO (7)] and of 3-X-methoxycyclohexane [X=F (8), Cl (9), Br (10), I (11), Me (12), NMe(2) (13) and MeO (14)] cis isomers were determined from low temperature NMR spectra and PCMODEL calculated coupling constants. The energy differences between aa and ee conformers were obtained from these data (DeltaG(J)(av) and DeltaG(PC)(av), respectively) and also by the additivity principle from data for the monosubstituted cyclohexanes (DeltaG(Ad)). H-1 and H-3 hydrogen vicinal coupling constants and DeltaG(J)(av) values showed that the diequatorial conformer is predominant in the conformational equilibrium of the compounds studied at low temperature. However, DeltaG(PC)(av) data show that compounds 6 and 7 constitute an exception, since they are almost equally populated by ee and aa at room temperature, due to stabilization of their aa conformer by an intramolecular hydrogen bond. DeltaG(Ad) values, obtained according to the additivity principle, show a better agreement for compounds 2 and 3, since the 1,3-diaxial steric effect is counterbalanced by the formation of an intramolecular hydrogen bond (IAHB). For the remaining compounds, DeltaG(Ad) values underestimate the energy differences, since the 1,3-diaxial steric effect, between X and OH or OCH(3), is absent in the monosubstituted compounds used as references. Moreover, the DeltaG(PC)(av), calculated from the coupling constants, obtained through the PCMODEL program, are rather smaller than the DeltaG(J)(av) values, since the program does not have parameters for the effect, observed in this report, of a substituent at gamma position on coupling constants values for the hydrogen under consideration.     

Micellisation of β-casein

We measured the dynamic (DLS) and static (SLS) light scattering behaviour of β-casein solutions in a 25 mM Na phosphate buffer at neutral pH as a function of temperature. At low temperatures (0 °C) β-casein is predominantly in a monomer state. With rising temperature micelles are formed with a (concentration-dependent) transition temperature in the range 15–30 °C. The transition is accompanied by a clear positive excess heat capacity. In DLS we observe two relaxation modes. The fast mode is attributed to the diffusive motion of the micelles and leads to a hydrodynamic radius of about 12 nm. The slow mode cannot be attributed to ‘physical’ particles. It is attributed to polydispersity or equivalently to long-range concentration fluctuations as proposed by Leclerc and Calmettes [15 and 16]. From SLS measurements we obtained the molecular mass and divided by the mass of a monomer (24 kDa) it gives the micellisation number, which seems to level off to about 30 at 40 °C. The measured micellisation number is predicted quite satisfactorily from a thermodynamic model for the calorimetric data as developed by Mikheeva et al. [26] and based on the shell model of Kegeles [24 and 25].     

New diagnostic of the most populated conformer of tetrahydrofuran in the gas phase

The most populated conformer of tetrahydrofuran (C(4)H(8)O) has been diagnosed as the Cs conformer in the present study, jointly using experimental electron momentum spectroscopy (EMS) and quantum mechanics. Our B3LYP/6-311++G** model indicates that the C1 conformation, which is one of the three possible conformations of tetrahydrofuran produced by pseudorotation in the gas phase, is a transition state due to its imaginary frequencies, in agreement with the prediction from a recent ab initio MP2/aug-cc-pVTZ study (J. Chem. Phys. 2005, 122, 204303). The study has identified the fingerprint of the highest occupied molecular orbital (HOMO) of the C(s) (12a') conformer as the most populated conformer. The identification of the C(s) structure, therefore, leads to the orbital-based assignment of the ionization binding energy spectra of tetrahydrofuran for the first time, on the basis of the outer valence Green function OVGF/6-31G* model and the density functional theory (DFT) SAOP/ET-PVQZ model. The present study explores an innovative approach to study molecular stabilities. It also indicates that energetic properties are not always the most appropriate means to study conformer-rich biological systems.     

3-Bromo-2-methyl-1-propene: molecular structure and conformation in the gas phase as determined by electron diffraction and molecular mechanics calculation

A gas phase electron diffraction study of 3-bromo-2-methyl-1-propene shows that there is predominantly a gauche conformer present. Data recorded at 20 and 180°C show 4(8) and 5(4)% respectively of a second confomer with a planar heavy atom skeleton. The gauche structural results in terms of r_a distances and angles at 20°C were found to be: r(C---C) = 1.331(9) Å, r(C---CH₂Br) = 1.484(6) Å, r(C---CH₃) — r(C---CH₂Br) = 0.017 Å, (assumed), r(C---Br) = 1.965(6) Å, C=C---CH₂Br = 121.5(0.7)°, C=C---CH₂Br — C=C---CH₃ = 0.7° (constraint from molecular mechanics calculation), C---C---Br = 112.2(0.5)°, torsional ANGLE = 112.5(2.2)°. Uncertainties are given as 2σ, where σ includes uncertainties due to correlation among observations, electron wavelength and other parameters used in the data reduction. The results obtained from the 180°C data agree very well with those given above. The molecular mechanics calculations yield information consistent with the experimental results.     

DFT studies of the structure, vibrational and NMR spectra of 2-amino-pyridine betaine monohydrate

Four of the most stable conformers of 2-amino-pyridine betaine (1-carboxymethyl-2-amino-pyridinium inner salt) monohydrates, 2-NH₂PB·H₂O, and one anhydrous were analyzed by the B3LYP/6-31G(d,p) calculations and compared with the X-ray data. Two types of optimized conformers can be distinguished: (a) with NH₂ and COO groups and (b) an imino tautomer with NH and COOH groups. A common feature of the optimized molecules are intramolecular hydrogen bonds between the COO⁻ and H₂N or COOH and HN groups. In the crystal both NH₂ and COO groups participate in intermolecular hydrogen bonds. The probable assignments of the anharmonic experimental solid state vibrational frequencies of 2-NH₂PB·H₂O and 2-ND₂PB·D₂O (conformer 2) based on the calculated B3LYP/6-31G(d,p) harmonic frequencies have been made. Correlations between experimental chemical shifts for 2-NH₂PB, its hydrochloride and 1-carboxyethyl-2-amino-pyridinium inner salt (¹³C and ¹H in D₂O) and GIAO/B3LYP/6-31G(d,p) calculated isotropic shielding constants, δ_exp=a+bσ_calc, are reported. Good linear regression between experimental and theoretical results for ¹³C was obtained. Only in 2-NH₂PB the hydrogen at -position is outside the linear correlation.     

Theoretical conformational analysis for neurotransmitters in the gas phase and in aqueous solution. Norepinephrine

The natural neurotransmitter (R)-norepinephrine takes the monocationic form in 93% abundance at the physiological tissue pH of 7.4. Ab initio and DFT/B3LYP calculations were performed for 12 protonated conformers of (R)-norepinephrine in the gas phase with geometry optimizations up to the MP2/6-311++G level, and with single-point calculations up to the QCISD(T) level at the HF/6-31G-optimized geometries. Four monohydrates were studied at the MP2/6-31G//HF/6-31G level. In the gas phase, the G1 conformer is the most stable with phenyl.NH(3)(+) gauche and HO(alc).NH(3)(+) gauche arrangements. A strained intramolecular hydrogen bond was found for conformers (G1 and T) with close NH(3)(+) and OH groups. Upon rotation of the NH(3)(+) group as a whole unit about the C(beta)-C(alpha) axis, a 3-fold potential was calculated with free energies for barriers of 3-12 kcal/mol at the HF/6-31G level. Only small deviations were found in MP2/6-311++G single-point calculations. A 2-fold potential was calculated for the phenyl rotation with free energies of 11-13 kcal/mol for the barriers at T = 310 K and p = 1 atm. A molecular mechanics docking study of (R)-norepinephrine in a model binding pocket of the beta-adrenergic receptor shows that the ligand takes a conformation close to the T(3) arrangement. The effect of aqueous solvation was considered by the free energy perturbation method implemented in Monte Carlo simulations. There are 4-5 strongly bound water molecules in hydrogen bonds to the conformers. Although hydration stabilizes mostly the G2 form with gauche phenyl.NH(3)(+) arrangement and a water-exposed NH(3)(+) group, the conformer population becomes T > G1 > G2, in agreement with the PMR spectroscopy measurements by Solmajer et al. (Z. Naturforsch. 1983, 38c, 758). Solvent effects reduce the free energies for barriers to 3-6 and 9-12 kcal/mol for rotations about the C(beta)-C(alpha) and the C(1)(ring)-C(beta) axes, respectively.     

Engineering the structure and magnetic properties of crystalline solids via the metal-directed self-assembly of a versatile molecular building unit

We report the supramolecular chemistry of several metal complexes of N-(4-pyridyl)benzamide (NPBA) with the general formula [Ma(NPBA)2AbSc], where M = Co2+, Ni2+, Zn2+, Mn2+, Cu2+, Ag+; A = NO3-, OAc-; S = MeOH, H2O; a = 0, 1, 2; b = 0, 1, 2, 4; and c = 0, 2. NPBA contains structural features that can engage in three modes of intermolecular interactions: (1) metal-ligand coordination, (2) hydrogen bonding, and (3) pi-pi stacking. NPBA forms one-dimensional (1-D) chains governed by hydrogen bonding, but when reacted with metal ions, it generates a wide variety of supramolecular scaffolds that control the arrangement of periodic nanostructures and form 1- (2-4), 2- (5), or 3-D (6-10) solid-state networks of hydrogen bonding and pi-pi stacking interactions in the crystal. Isostructural 7-9 exhibit a 2-D hydrogen bonding network that promotes topotaxial growth of single crystals of their isostructural family and generates crystal composites with two (11) and three (12) different components. Furthermore, 7-9 can also form crystalline solid solutions (M,M')(NPBA)2(NO3)2(MeOH)2 (M, M' = Co2+, Ni2+, or Zn2+, 13-16), where mixtures of Co2+, Ni2+, and Zn2+ share the same crystal lattice in different proportions to allow the formation of materials with modulated magnetic moments. Finally, we report the effects that multidimensional noncovalent networks exert on the magnetic moments between 2 and 300 K of 1-D (4), 2-D (5), and 3-D (7, 8, 10, and 13-16) paramagnetic networks.     

Synthesis and crystal structure of two novel nickel (imidazole) complexes having hydrogen-bonded networks

Two nickel (imidazole) complexes, Ni(im)₆Cl₂·4H₂O (1) and Ni(im)₆(NO₃)₂ (2) (im=imidazole) have been synthesized and characterized by elemental analysis, IR, UV, TG and single crystal X-ray diffraction. 1 crystallizes in the triclinic space group P-1 with a=8.800(6) Å, b=9.081(6) Å, c=10.565(7) Å, =75.058(9)°, β=83.143(8)°, γ=61.722(8)°, V=718.3(8) Å³, Z=1 and R₁ (wR₂)=0.0469 (0.1497). 2 crystallizes in the trigonal space group R-3 with a=12.370(6) Å, b=12.370(6) Å, c=14.782(14) Å, =90.00°, β=90.00°, γ=120.00°, V=1959(2) Å³, Z=3 and R₁ (wR₂)=0.0358 (0.0955). 1 and 2 exhibit different supramolecular network due to their different counter anions and different hydrogen bonding connection. In compound 1, [Ni(im)₆]²⁺ cation and counter anions Cl⁻ alternatively array in an ABAB fashion via N–HCl hydrogen bonding. In compound 2, the plane of each NO₃²⁻ is almost parallel and each NO₃²⁻ connect three different [Ni(im)₆]²⁺ cations via N–HO hydrogen bonding.     

Kinetics of formation of intermediates in silver ion assisted aquations

There is kinetic evidence of the formation of [Co(NH₃)₅NCSAg₃]⁵⁺ in the interaction of [Co(NH₃]⁵NCS]²⁺ with Ag⁺ in aqueous solution, with pseudo-first-order formation rate constant k = 0.158 s⁻¹ for the forward reaction in the following equation at 25°C and [Ag⁺] in the range of 1.23–5.0 × 10⁻² mol dm⁻³ and 0.10 ionic strength (NaClO₄):

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Additionally, the formation constant, β₂, for [Co(NH₃)₅NCSAg₂]⁴⁺ has been determined to be log β₂ = 4.717. For the [Rh(NH₃)₅I]²⁺-Ag⁺ reaction there is evidence of an outer-sphere interaction with rate constants of k₂ = 670 dm³ mol⁻¹ s⁻¹ at 25°C and 0.10 ionic strength. This outer-sphere species undergoes further reaction to give the silver ion containing intermediates of the aquation reactions.     

Ureidopyrimidinones incorporating a functionalizable p-aminophenyl electron-donating group at C-6

[structure: see text] 2-Ureido-4-[1H]-pyrimidinones have been reported to dimerize via quadruple hydrogen bonding systems with dimerization constants >10(6) M(-1) in CDCl3. The dimerization constant, K(dim), is dependent on the solvent as well as the ring-substituents present, where previously alkyl (e.g., R1 = Me) and aromatic moieties (e.g., R1 = p-NO2C6H4, R1 = C6H2(OC13H27)3) have been incorporated at the C-6 position. To assess the influence of alternative, functionalizable, electron-donating groups on the dimerization motif and tautomeric distribution of isomers, the synthesis of compounds possessing aminophenyl functionality at the C-6 position has been achieved. NMR spectroscopy chemical shift analysis revealed that compound 2 (R1 = p-NH2C6H4, R2 = C6H13) existed as the 2-ureido-4-pyrimidinol dimeric DADA array in DMSO-d6, where a dimerization constant of 46 M(-1) was determined. This is the first time that a ureidopyrimidinone quadruple hydrogen bonding DADA array has been observed in pure DMSO, a highly polar solvent. The azo-derivative 5 of compound 2 was prepared which also adopted the pyrimidin-4-ol form in DMSO-d6. Compounds 7, 10 and 11 were then synthesized containing a more hydrophilic PEG unit in the lateral chain and the tautomeric distributions were determined.     

Isolation of a diketone species that is allylically bound to tungsten, and its relationship to a tungsten η-ketone complex

The diketone complex [W(CO)₂(η-C₅H₄Me){η³-

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(H)---C(O)---C₅Me₅}] (3) was isolated from the reaction of PhC₂H with a mixture of [Ni(CO)I(η-C₅Me₅)] and [W(CO)₃(η-C₅H₄Me)]⁻. Complex 3 contains an organic diketone fragment that is bound in a π-allyl fashion to a tungsten atom. It was fully characterized by standard spectroscopic techniques and by a single-crystal X-ray diffraction study. The relationship of complex 3 to a structurally characterized cyclopentadienyl tungsten η²-ketone species 1, and the likelihood that 3 and the methylcyclopentadienyl analog of 1 share common intermediates, are discussed.     

Chemistry of polyfunctional molecules-123. Reactions of BiBr3, SbI3 and AsI3 with LiN(PPh2)2; X-ray structure of a cyclophosphazene salt containing arsenic(I)

BiBr₃ or SbI₃ react at 20°C with LiN(PPh₂)₂ (1) to give elementary Bi or Sb and the P---P coupled phosphazene ligand Ph₂P---N=PPh₂---PPh₂=N---PPh₂ (2). The reaction of AsI₃ with 1 at room temperature formed yellow needles of the eight-membered heterocycle (3), whereas AsI₃ interacted at 80°C with 1 in the molar ratio of 1:3 to give elementary arsenic and 2. Treatment of AsI₃ and 1 at 20°C in a 1:2 stoichiometry yielded the seven-membered, cyclic arsenium(I) salt

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I·4THF (5·4THF), which was characterized by elemental analysis, conductivity, mass, IR and NMR spectroscopy and single-crystal X-ray structural analysis.     

Simple charge transfer complexes of some new and of some known heterocyclic compounds of selenium and tellurium

Charge transfer (CT) complexes (1:1) of 2,5-dihydrotellurophene and the 3-methyl and 3,4-dimethyl compounds with TCNQ and tetrachlorobenzoquinone (TCB) are reported. The organotellurium compounds failed to give complexes with p-dinitrobenzene (DNB). The variation of solid state (disc) conductivity with temperature and as a function of methyl substituents is considered. The complexes show semi-conducting behaviour and a consideration of these data, together with IR and UV spectroscopic data, in comparison with those for 1,3-dihydro-2-telluraindene given the following order of donor power with respect to TCNQ:

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With respect to a given donor, the order to acceptor power is TCNQ> TCB> DNB.

1,3-Dihydro-2-selanaindene forms a complex with TCNQ. The molecular ionisation potential of the selanaindene is 7.4 eV (by mass spectroscopy) and it has been shown that the compound may be electrochemically oxidized to materials such as C₈H₈SePF₆.

New quinoxalino-1-chalcogenacyclopentanes are reported; namely those derived from selenium, and for the 7,8-dimethyl series, those based on both selenium and tellurium. Their preparation and characterisation are described, and their chemistry shown to be strongly analogous to that of quinoxalino-1-telluracyclopentane. CT complexes of the new Se^II and Te^II compounds (1:1) are prepared with TCNQ which are believed to be strongly ionic.     

Microcalorimetric studies on catalase reaction and inhibition of catalase by cyanide ion

As Chance et al. [1, 2 and 3] proposed, the decomposition of hydrogen peroxide catalyzed by catalase is an overall first-order reaction. In this paper, we have studied this enzyme-catalyzed reaction with a thermokinetic method. The rate constant and the molar reaction enthalpy of this reaction have been measured. At 310.15 K and pH=8.2, k_cat=1.75×10⁶ l mol⁻¹ s⁻¹, Δ_rH_m=88.99 kJ mol⁻¹. Furthermore, we have studied the competitive inhibition of catalase by cyanide ion and reported some correlated parameters.