Studies of the roles of Sn or Fe on γ-Al2O3-supported Pt catalysts by CO adsorption microcalorimetry and dehydrogenation reaction of C4 alkanes

CO adsorption microcalorimetry was employed in the study of γ-Al₂O₃-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al₂O₃ catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-N₂O₃ catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and Fe to the Pt/γ-Al₂O₃ catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential heat of 60–110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was changed by adding Sn or Fe to Pt/γ-N₂O₃. The distribution of differential heat of CO adsorption on the Pt-Sn(C)/γ-Al₂O₃ catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C₄ alkanes with the number of CO adsorption sites with differential heat of 60–110 kJ/mol showed a good correlation. These results indicate that the surface Pt centers with differential heats of 60–110 kJ/mol for CO adsorption possess superior activity for the dehydrogenation of alkanes. Project supported by FORD and the National Natural Science Foundation of China (Grant No. 09412302) and the Transcentury Training Program Foundation for the Talents by The State Education Commission of China.     

The study of chemical reactions, absorption and extraction, using apparatuses with serpentine pie for pelliclizing-bubbling, XIV. Hydroperoxidation of 1,3-diisopropylbenzene with oxygen

Experimental results obtained by thermal hydroperoxidation of 1,3-diisopropylbenzene in the temperature region of 102–105°C, using a Vodnár-1 type apparatus with discontinuous operation are presented. Based on the results, the activation energy (E=48.5±2 kJ/mol), enthalpy (ΔH⁺=47±2 kJ/mol), entropy (ΔS⁺) and the activation free enthalpy (ΔG⁺) were calculated. XIII. J. Vodnár, A. Chis, A. Biro, S. Békássy and M. Dragan:Studia Univ. Babes-Bolyai, Chemia, Cluj-Napoca, 1997,42, 2.     

Sr<Superscript>+</Superscript> + H<Subscript>2</Subscript>O ↔ SrOH<Superscript>+</Superscript> + H equilibrium in flames with strontium admixtures

Sr⁺ + H₂O ↔ SrOH⁺ + H equilibrium was studied spectrophotometrically. This reaction occurs in natural gas combustion products. Its enthalpy Δ_r H ^○(0) = 61.4 ± 2.8 kJ/mol and bond energy D ₀(Sr⁺-OH) = 432.6 ± 2.8 kJ/mol were determined using the third law of thermodynamics. The experimental data on this reaction obtained earlier in hydrogen flames, Δ_r H ^○(0) = 55.3 ± 10.6 and D ₀(Sr⁺-OH) = 438.7 ± 10.6 kJ/mol, were interpreted anew. The D ₀(Sr⁺-OH) = 432.8 ± 2.7 kJ/mol value was eventually obtained.     

Stationary points on the energy hypersurface of the reaction O3 + H•→ [•O3H]* ⇆ O2 + •OH and thermodynamic functions of •O3H at G3MP2B3, CCSD(T)-CBS (W1U) and MR-ACPF-CBS levels of theory

The relative enthalpies, ΔH^o (0) and ΔH^o (298.15), of stationary points (four minimum and three transition structures) on the ^•O₃H potential energy surface were calculated with the aid of the G3MP2B3 as well as the CCSD(T)–CBS (W1U) procedures from which we earlier found mean absolute deviations (MAD) of 3.9 kJ mol⁻¹ and 2.3 kJ mol⁻¹, respectively, between experimental and calculated standard enthalpies of the formation of a set of 32 free radicals. For CCSD(T)-CBS (W1U) the well depth from O₃ + H^• to trans-^•O₃H, ΔH^o_well(298.15) = −339.1 kJ mol⁻¹, as well as the reaction enthalpy of the overall reaction O₃ + H^•→O₂ + ^•OH, Δ_rH^o(298.15) = −333.7 kJ mol⁻¹, and the barrier of bond dissociation of trans-^•O₃H → O₂ + ^•OH, ΔH^o(298.15) = 22.3 kJ mol⁻¹, affirm the stable short-lived intermediate ^•O₃H. In addition, for radicals cis-^•O₃H and trans-^•O₃H, the thermodynamic functions heat capacity C^o_p(T), entropy S^o (T), and thermal energy content H^o(T) − H^o(0) are tabulated in the range of 100 − 3000 K. The much debated calculated standard enthalpy of the formation of the trans-^•O₃H resulted to be Δ_fH^o(298.15) = 31.1 kJ mol ⁻¹ and 32.9 kJ mol ⁻¹, at the G3MP2B3 and CCSD(T)-CBS (W1U) levels of theory, respectively. In addition, MR-ACPF-CBS calculations were applied to consider possible multiconfiguration effects and yield Δ_fH^o(298.15) = 21.2 kJ mol ⁻¹. The discrepancy between calculated values and the experimental value of −4.2 ± 21 kJ mol⁻¹ is still unresolved. Note added in proof: Yu-Ran Luo and J. Alistair Kerr, based on the discussion in reference 12, recently presented an experimental value of Δ_fH^o(298.15) = 29.7 ± 8.4 kJ mol⁻¹ in the 85th edition of the CRC Handbook of Chemistry and Physics (in progress).     

Electrolytic molybdenum sulfides for thin-layer lithium power sources

The active molybdenum sulfide compound Mo₂S₃, which should be considered as a cathode material for thin-layer rechargeable power source, has been produced by electrolysis. Using impedance spectroscopy and potential relaxation method after current interruption, the kinetic parameters of lithium intercalation in electrolytic Mo₂S₃ have been obtained. Activation energy of Li⁺ migration in electrolyte (13.76 kJ/mol), charge transfer through the Mo₂S₃ electrode/electrolyte interface (38.8 kJ/mol), and Li⁺ diffusion in a solid phase (57.3 kJ/mol) have also been established. Taking into account the coefficient data of charge mass transfer in a solid phase and the reaction rate coefficient of charge transfer through the interface electrode/electrolyte within the temperature range 20–50 °C, the stage of Li⁺ transfer in a solid phase has been determined as a limiting stage for lithium intercalation in electrolytic molybdenum sulfide Mo₂S₃.     

Thermochemical properties of the Fe-analogue of cryolite, Na3FeF6

Relative enthalpies for low-and high-temperature modifications of Na₃FeF₆ and for the Na₃FeF₆ melt have been measured by drop calorimetry in the temperature range 723–1318 K. Enthalpy of modification transition at 920 K, δ_trans H(Na₃FeF₆, 920 K) = (19 ± 3) kJ mol⁻¹ and enthalpy of fusion at the temperature of fusion 1255 K, δ_fusH(Na₃FeF₆, 1255 K) = (89 ± 3) kJ mol⁻¹ have been determined from the experimental data. Following heat capacities were obtained for the crystalline phases and for the melt, respectively: C _p(Na₃FeF₆, cr, α) = (294 ± 14) J (mol K)⁻¹, for 723 = T/K ≤ 920, C _p(Na₃FeF₆, cr, β) = (300 ± 11) J (mol K)⁻¹ for 920 ≤ T/K = 1233 and C _p(Na₃FeF₆, melt) = (275 ± 22) J (mol K)⁻¹ for 1258 ≤ T/K ≤ 1318. The obtained enthalpies indicate that melting of Na3FeF6 proceeds through a continuous series of temperature dependent equilibrium states, likely associated with the production of a solid solution.      

Di-tert-butyl(N-pyrrolyl)phosphane,-sulfide, and-selenide, studied by multinuclear magnetic resonance

 Di-tert-butyl(N-pyrrolyl)phosphane (1),-sulfide (2) and-selenide (3) were studied by ¹H, ¹³C, ¹⁵N, ³¹P and ⁷⁷Se NMR spectroscopy in solution. Restricted rotation about the P–N bond was observed for 1 (ΔG^≠ _C≈58.5 kJ/mol) and 2, 3 (ΔG^≠ _C≈45 kJ/mol) by ¹H and ¹³C NMR at variable temperature. The fairly high pyrrolyl rotation barrier in 1 is ascribed to the expected steric effects exerted by the tert-butyl groups and to repulsion between the lone pairs of electrons at the phosphorus and nitrogen atoms. These repulsive forces are reduced in 2 or 3, or in di-tert-butyl(phenyl) phosphane (ΔG^≠ _C≈44 kJ/mol). Signs of coupling constants ⁿJ(³¹P, ¹³C) and ⁿ⁺¹J(³¹P, ¹H) (n=2, 3) were determined by two-dimensional (2D) ¹³C/¹H heteronuclear shift correlations. The preferred orientation of the pyrrolyl group in 1 is evident from the coupling constants ²J(³¹P, ¹³C(2))=+35.4 Hz and ²J(³¹P, ¹³C(5))=−9.3 Hz, typical of C(2) in syn and C(5) in anti position with respect to the assumed axis of the phosphorus lone pair. Hahn-echo extended (HEED) polarization transfer pulse sequences served for measuring ¹J(³¹P, ¹⁵N) and isotope induced chemical shifts ¹Δ^15/14N(³¹P) from ³¹P NMR spectra. Received: 4 April 1996/Revised: 6 May 1996/Accepted: 11 May 1996     

Di-tert-butyl(N-pyrrolyl)phosphane,-sulfide, and-selenide, studied by multinuclear magnetic resonance

 Di-tert-butyl(N-pyrrolyl)phosphane (1),-sulfide (2) and-selenide (3) were studied by ¹H, ¹³C, ¹⁵N, ³¹P and ⁷⁷Se NMR spectroscopy in solution. Restricted rotation about the P–N bond was observed for 1 (ΔG^≠ _C≈58.5 kJ/mol) and 2, 3 (ΔG^≠ _C≈45 kJ/mol) by ¹H and ¹³C NMR at variable temperature. The fairly high pyrrolyl rotation barrier in 1 is ascribed to the expected steric effects exerted by the tert-butyl groups and to repulsion between the lone pairs of electrons at the phosphorus and nitrogen atoms. These repulsive forces are reduced in 2 or 3, or in di-tert-butyl(phenyl) phosphane (ΔG^≠ _C≈44 kJ/mol). Signs of coupling constants ⁿJ(³¹P, ¹³C) and ⁿ⁺¹J(³¹P, ¹H) (n=2, 3) were determined by two-dimensional (2D) ¹³C/¹H heteronuclear shift correlations. The preferred orientation of the pyrrolyl group in 1 is evident from the coupling constants ²J(³¹P, ¹³C(2))=+35.4 Hz and ²J(³¹P, ¹³C(5))=−9.3 Hz, typical of C(2) in syn and C(5) in anti position with respect to the assumed axis of the phosphorus lone pair. Hahn-echo extended (HEED) polarization transfer pulse sequences served for measuring ¹J(³¹P, ¹⁵N) and isotope induced chemical shifts ¹Δ^15/14N(³¹P) from ³¹P NMR spectra. Received: 4 April 1996/Revised: 6 May 1996/Accepted: 11 May 1996     

On the Importance of H-Bonding Interactions in Organic Ammonium Tetrathiotungstates

Summary. Four new organic ammonium tetrathiotungstates (N–Me–enH₂)[WS₄] (1), (N,N′-dm-1,3-pnH₂)[WS₄] (2), (1,4-bnH₂)[WS₄] (3), and (mipaH)₂[WS₄] (4), (N–Me–enH₂ = N-methylethylenediammonium, N,N′-dm-1,3-pnH₂ = N,N′-dimethyl-1,3-propanediammonium, 1,4-bnH₂ = 1,4-butanediammonium, and mipaH = monoisopropylammonium) were synthesized by the base promoted cation exchange reaction and characterized by elemental analysis, infrared, Raman, UV-Vis and ¹H NMR spectroscopy as well as single crystal X-ray crystallography. The structures of 1–4 consist of [WS₄]²⁻ tetrahedra which are linked to the organic ammonium cations via N–H⋯S hydrogen bonding. The strength and number of the S⋯H interactions affect the W–S bond lengths as evidenced by distinct short and long W–S bonds. The IR spectra exhibit splitting of the W–S vibrations, which can be attributed to the distortion of the [WS₄]²⁻ tetrahedron. From a comparative study of several known tetrathiotungstates it is observed that a difference of more than 0.033 ? between the longest and shortest W–S bonds in a tetrathiotungstate will result in the splitting of the asymmetric stretching vibration of the W–S bond.     

Preparation and characterization of nanotube Li-Ti-O by molten salt method

Nanotube Li-Ti-O compound with high surface (198.6 m²·g⁻¹) was prepared by a method involving the treatment of nanotube Na₂Ti₂O₅·H₂O in molten LiNO₃ and characterization by means of transmission electron microscopy (TEM), energy-dispersive spectra (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry-differential thermal analysis (TG/DTG). Results show that the nanotube Li-Ti-O compound prepared by this method involves two crystal phases: spinel Li₂Ti₂O₄ and anatase Li_xTiO₂ (x < 0.1). Li⁺ exhibits different Li1s binding energy in the two crystal phases. In ambient air, the Li-Ti-O compound adsorbs water easily, and the chemically adsorbed water is difficult to remove below 400°C. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(12): 2135–2139 [译自: 无机化学学报]     

Preparation and characterization of lithium ion-conducting glass-ceramics in the Li1 + xCrxGe2 − x(PO4)3 system

Li₂O–Cr₂O₃–GeO₂–P₂O₅ based glasses were synthesized by a conventional melt-quenching method and successfully converted into glass-ceramics through heat treatment. Experimental results of DTA, XRD, ac impedance techniques and FESEM indicated that Li_1.4Cr_0.4Ge_1.6(PO₄)₃ glass-ceramics treated at 900 °C for 12 h in the Li_1 + xCr_xGe_2 − x(PO₄)₃ (x = 0–0.8) system exhibited the best glass stability against crystallization and the highest ambient conductivity value of 6.81 × 10⁻⁴ S/cm with an activation energy as low as 26.9 kJ/mol. In addition, the Li_1.4Cr_0.4Ge_1.6(PO₄)₃ glass-ceramics displayed good chemical stability against lithium metal at room temperature. The good thermal and chemical stability, excellent conducting property, easy preparation and low cost make it promising to be used as solid-state electrolytes for all-solid-state lithium batteries.     

Cisapride/β-cyclodextrin complexation: stability constants, thermodynamics, and guest–host interactions probed by 1H-NMR and molecular modeling studies

Phase solubility techniques were used to obtain the complexation parameters of cisapride (Cisp) with β-cyclodextrin (β-CD) in aqueous 0.05 M citrate buffer solutions. From the UV absorption spectra and the pH solubility profile, two basic pK _as were estimated: pK _a(1+) = 8.7 and pK _a(2+) < 2. The inherent solubility (S _o) of Cisp was found to increase as pH decreases, but is limited by the solubility product of the CispH⁺·citrate¹⁻ salt at low pH (pK _sp = 3.0). Cisp forms soluble 1:1 and 1:2 Cisp/β-CD complexes. A quantitative measure of the hydrophobic effect (desolvation) contribution to 1:1 complex formation was obtained from the linear variation of free energy of 1:1 Cisp/β-CD complex formation (ΔG ₁₁ = −RT ln K ₁₁ < 0) with that of the inherent solubility of Cisp . The results show that the hydrophobic character of Cisp contributes about 35% of the total driving force to 1:1 complex formation (slope = −0.35), while other factors, including specific interactions, contribute −10.6 kJ/mol (intercept). Protonated 1:1 Cisp/β-CD complex formation at pH 6.0 is driven by favorable enthalpy (ΔH° = −9 kJ/mol) and entropy (ΔS° = 51 J/mol K) changes. In contrast, inherent Cisp solubility is impeded by unfavorable enthalpy (ΔH° = 12 kJ/mol) and entropy (ΔS° = 90 J/mol K) changes. ¹H-NMR spectra in D₂O and molecular mechanical studies indicate the formation of inclusion complexes. The dominant driving force for neutral Cisp/β-CD complexation in vacuo was predominantly van der Waals with very little electrostatic contribution.     

Synthesis,Characterization, and Crystal Structures of Metal Amide Cage Complexes Containing a M<Subscript>4</Subscript>O<Subscript>4</Subscript> (M = Nb,Ta) Core Unit

Metal cage complexes [(Me₂N)₃MO]₄ (M = Nb, 3; Ta, 4) have been prepared from the reactions of M(NMe₂)₅ (M = Nb, 1; Ta, 2) with water. Single crystal X-ray diffraction studies of 3 and 4 reveal that they adopt cubane-like structures with M–O bridges. Variable-temperature NMR studies of –NMe_AMe_B rotations in 3 and 4 have been performed to give the following activation parameters for the exchanges: ΔH ^≠ = −1.4(1.1) kJ/mol, ΔS ^≠ = −209(8) J/mol K, \Updelta G _{30 8  \textK} ¹ = 6 4( 2)  \textkJ/\textmol \Updelta G_{{_{{ 30 8\;{\text{K}}}} }}^{{^{ \ne } }} = 6 4\left( 2\right)\;{\text{kJ}}/{\text{mol}} for 3, and ΔH ^≠ = −0.9(1.2) kJ/mol, ΔS ^≠ = −2.1(0.2) × 10² J/mol K, \Updelta G _{30 8  \textK} ¹ = 6 3( 6)  \textkJ/\textmol \Updelta G_{{ 30 8\;{\text{K}}}}^{{^{ \ne } }} = 6 3\left( 6\right)\;{\text{kJ}}/{\text{mol}} for 4.     

Ab initio study on the mechanism of reaction HNCO+NH2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH₂+ HNCO?NH₃+NCO (1) and NH₂+HNCO?N₂H₃+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300–2700 K, transition theory rate constant for reaction (1) is 1.68×10¹¹–3.29×10¹¹ mL·mol^-1·s^-1, which is close to the experimental one of 5.0×10¹¹mL·mol^-1·s^-1or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes,cis andtrans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (forcis-mode) and 147.43 kJ/mol (fortrans-mode), respectively, which is much higher than reaction (1). So reaction (1) is the main channel for the titled reaction.     

The C2H 3 + cation and its interaction with HF

The structure and stability of classical and bridged C₂H ₃ ⁺ is reinvestigated. The SCF and CEPA-PNO computations performed with flexibles andp basis sets including twod-sets on carbon confirm our previous results. We find the protonated acetylene structure to be more stable than the vinyl cation by 3.5–4 kcal/mol. The energy barrier for the interconversion of these two structures is at most a few tenths of a kcal/mol. The equilibrium SCF geometries of Weberet al. [15] are affected insignificantly by further optimization at the CEPA-PNO level. Several structures for the interaction of C₂H ₃ ⁺ with HF have been investigated at the SCF level. With our largest basis set which includes a complete set of polarization functions we find a remarkable levelling of the stabilities of most of the structures. In these cases the stabilization energy ΔE ranges from −10 to −13 kcal/mol.     

Potential energy profiles of the geometric isomerization and the thermal decomposition of diphosphene HP=PH in the ground and excited electronic states

Summary The geometric isomerization and the dehydrogenation of HP=PH in the ground and some low-lying excited states are investigated by theoretical calculations. The reaction paths are traced by either the CASSCF or UHF-SCF calculations using the 6-31G(d,p) basis functions, and the accompanying energy changes are calculated by the MRD-CI method employing the [5s3p1d]/[2s1p] basis functions. The barrier heights for the trans-to-cis isomerization, by the planar inversion and the nonplanar twisting, in the ground state are calculated to be 265 and 144 kJ/mol (with the vibrational zero-point energy corrections), respectively. The latter barrier is noticeably lower than the H-P and the P-P bond dissociation energies oftrans-HP=PH (¹A_g), which are 304 and 271 kJ/mol, respectively. The ground-state HP₂ radical (²A'), which is to be formed by the dehydrogenation of HP=PH, should suffer further decomposition into P₂ (¹ _g ⁺ ) and H with an activation energy of 139 kJ/mol. The lowest excited state of HP₂ is found to be a hydrogen-bridged 3-electron system (²A₂) having an isosceles triangle structure. It has proved to be formed by the dehydrogenation of the lowest excited singlet state (¹B) of HP=PH via a transition state which lies 194 kJ/mol above the¹B state. The excited HP₂ (²A₂) is state-correlated with P₂ (³_u)+H.     

Nano Au/TiO2 hollow microsphere membranes for the improved sensitivity of detecting specific DNA sequences related to transgenes in transgenic plants

Gold nanoparticles (nano Au)/titanium dioxide (TiO₂) hollow microsphere membranes were prepared on the carbon paste electrode (CPE) for enhancing the sensitivity of DNA hybridization detection. The immobilization of nano Au and TiO₂ microsphere was investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization events were monitored with EIS using [Fe(CN)₆]^3−/4− as indicator. The sequence-specific DNA of the 35S promoter from cauliflower mosaic virus (CaMV35S) gene was detected with this DNA electrochemical sensor. The dynamic detection range was from 1.0×10⁻¹² to 1.0×10⁻⁸ mol/L DNA and a detection limit of 2.3×10⁻¹³ mol/L could be obtained. The polymerase chain reaction (PCR) amplification of the terminator of nopaline synthase (NOS) gene from the real sample of a kind of transgenic soybean was also satisfactorily detected. Supported by the National Natural Science Foundation of China (Grant Nos. 20635020 and 20375020), Doctoral Foundation of the Ministry of Education of China (Grant No. 20060426001) and Natural Science Foundation of Qingdao City (Grant No. 04-2-JZP-8)     

Conformational study of a strained tolanophane by dynamic 1H NMR spectroscopy and computational methods

The existence of a short C–H ⋯ π (alkyl–alkyne) interaction in the structure of a strained and relatively rigid tolanophane is expected to hinder the rotation about the C–C sp³ single bond. Variable-temperature NMR experiments (performed in three solvents, CDCl₃, THF-d₈, and acetone-d₆) and ab initio density functional calculations were carried out to investigate its dynamic nature. An energy barrier of 48.6 kJ/mol is determined at coalescence (210 K) with acetone-d₆ which is in good agreement with calculation result (54 kJ/mol). Correspondence: Hossein Reza Darabi, Chemistry and Chemical Engineering Research Center of Iran, Pajoohesh Blvd., km 17, Karaj Hwy, 14968-13151 Tehran, Iran.     

Thermochemical properties of trialkylarsenites

The heats of the reaction of sodium with ethyl and methyl alcohol were determined by calorimetry. The difference in the standard heats of the formation of triethylarsenite and arsenic trichloride was obtained by calorimetration of the reaction of arsenic trichloride with sodium ethylate, the value of which was −382.42 ± 3.60 kJ/mol. The standard enthalpies of formation were determined from a critical analysis of all data on thermochemistry of trialkylarsenites for the following compounds: triethylarsenite Δ_f H ₂₉₈^ℴ [(C₂H₅O)₃As(liquid)] = (−704.38 ± 3.85) kJ/mol; trimethylarsenite Δ_f H ₂₉₈^ℴ [(CH₃O)₃As(liquid)] = (−599.36 ± 1.88) kJ/mol. The values of standard enthalpies of formation were not adjusted for the following substances in liquid state: arsenic trichloride (−321.96 ± 3.85 kJ/mol), tris-(diethylamido)arsenic(III) As(NEt₂)₃(liquid) (−129.81 ± 4.41 kJ/mol), tri-n-propylarsenite (−720.61 ± 4.49 kJ/mol), triisopropylarsenite (−756.11 ± 4.65 kJ/mol), tri-n-butylarsenite (−775.11 ± 4.53 kJ/mol), and triisobutylarsenite (−809.71 ± 4.59 kJ/mol). The use of sodium alcoxide solutions for the calorimetration of halogen anhydrides of various acids was demonstrated.