The Temperature‐Composition Phase Equilibria in the Hg0.8Cd0.2Te‐HgI2 Pseudobinary System

The temperature‐composition phase equilibria of the Hg_0.8Cd_0.2Te‐HgI₂ system were investigated between about 100 and 800 °C using Debye‐Scherrer powder X‐ray diffraction techniques, differential thermal analysis, differential scanning calorimetry, and thermochemical and structural calculations. This system is a pseudobinary temperature‐ composition plane in the HgTe‐CdTe‐HgI₂ pseudoternary phase diagram. Measurable solid solutions of HgI₂ in Hg_0.8Cd_0.2Te with the cubic zinc blende‐type structure exist between about 290 and 700 °C, with a maximum solubility of 4.9 ± 0.3 mole‐% HgI₂ at 363 ± 3 °C. Further addition of HgI₂ to HgI₂‐saturated Hg_0.8Cd_0.2Te yields the formation of CdI₂, which reduces the mole fraction (x) of CdTe in the Hg_1—xCd_xTe host lattice. After sufficient HgI₂ is added, the host lattice is depleted in CdTe and forms Hg₃Te₂I₂ in addition to CdI₂. Phase fields containing the ternary compound Hg₃TeI₄, which we first observed in the HgTe‐HgI₂ system, also exist in the present system. Quaternary analogs of the known ternary compounds Hg₃Te₂I₂ and Hg₃TeI₄, i.e., Hg_3—yCd_yTe₂I₂ and Hg_3—yCd_yTeI₄, were not observed under present experimental conditions.     

The temperature-composition phase diagram of the HgTe?HgI2 pseudobinary system on the HgTe rich side

The temperature-composition phase diagram of the HgTe? HgI₂ system was determined from 0 to 45 Mol-% HgI₂ between 25 and 670°C using Debye-Scherrer powder X-ray diffraction techniques and differential thermal analysis. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7 ± 0.8 Mol-% HgI₂ in HgTe at 501 ± 5°C. The known monoclinic compound Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501 ± 5°C, with the peritectic point at approximately 37 ± 4 Mol-% HgI₂.     

The Temperature-Composition Phase Equilibria in the HgTe–HgI2 Pseudobinary System

The temperature-composition phase diagram of the HgTe—HgI₂ pseudobinary system was determined between 25 and 670°C using differential scanning calorimetry, differential thermal analysis, Debye-Scherrer powder X-ray diffraction techniques, and metallographic analysis methods. Solid solutions of HgTe and HgI₂ with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7±0.8 Mol-% HgI₂ in HgTe at 501±5°C. The monoclinic intermediate phase Hg₃Te₂I₂ is formed by a peritectic reaction upon cooling at 501±5°C, with the peritectic point at approximately 37±4 Mol-% HgI₂. The previously unknown cubic phase Hg₃TeI₄ (a = 6.240±0.003 Å) is formed by a eutectoid reaction at 238±3°C and is stable up to 273±3°C, where it melts by a peritectic reaction with the peritectic point at approximately 79±3 Mol-% HgI₂. Between Hg₃TeI₄ and HgI₂ is a eutectic point at 82±3 Mol-% HgI₂ and 250±3°C. The α to β transition of HgI₂ at 133±3°C is independent of sample composition between 33.3 and 100 Mol-% HgI₂.     

Ein Beitrag über Sr2RuO4 und Sr3Ru2O7 Zur Oktaederstreckung von M4+ in K2NiF4- und Sr3Ti2O7-Typ-Verbindungen

On the Thermal Decomposition of Hg₂I₂ and the Hg? I State Diagram Solid Hg₂I₂ decomposes congruently in Hg and HgI₂. The entropy S°(Hg₂I₂,s,298) = (55,5 ± 1) cal/K · mol and the enthalpy of formation ΔH_f°(Hg₂I₂, s, 298) = (?30,0 ± 2) kcal/mol are derived from the decomposition equilibrium. The phase diagram of the whole system Hg? I was constructed from investigations by DTA and total pressure measurements in the partial systems Hg? Hg₂I₂, Hg₂I₂? HgI₂, and HgI₂? I₂. It follows, that Hg₂I₂ melts incongruently at 297°C and decomposes in a Hg-rich and HgI₂-rich melt. The emerging miscibility gap is assumed to close at a temperature near 500°C.     

Crystal Structure of the Mixed‐Valent Basic Mercury Nitrate HgI2(NO3)2·HgII(OH)(NO3)·HgII(NO3)2·4HgIIO [= Hg8O4(OH)(NO3)5]

Light‐yellow single crystals of the mixed‐valent mercury‐rich basic nitrate Hg₈O₄(OH)(NO₃)₅ were obtained as a by‐product at 85 °C from a melt consisting of stoichiometric amounts of (Hg^I₂)(NO₃)₂·2H₂O and Hg^II(OH)(NO₃). The title compound, represented by the more detailed formula Hg^I₂(NO₃)₂·Hg^II(OH)(NO₃)·Hg^II(NO₃)₂·4Hg^IIO, exhibits a new structure type (monoclinic, C2/c, Z = 4, a = 6.7708(7), b = 11.6692(11), c = 24.492(2) Å, β = 96.851(2)°, 2920 structure factors, 178 parameters, R1[F² > 2σ(F²)] = 0.0316) and is made up of almost linear [O‐Hg^II‐O] and [O‐Hg^I‐Hg^I‐O] building blocks with typical Hg^II‐O distances around 2.06Å and a Hg^I‐O distance of 2.13Å. The Hg₂²⁺ dumbbell exhibits a characteristic Hg‐Hg distance of 2.5079(7) Å. The different types of mercury‐oxygen units form a complex three‐dimensional network exhibiting large cavities which are occupied by the nitrate groups. The NO₃^? anions show only weak interactions between the nitrate oxygen atoms and the mercury atoms which are at distances > 2.6Å from one another. One of the three crystallographically independent nitrate groups is disordered.     

Syntheses,Characterization, and Crystal Structures of a Dinuclear Complex and Coordination Polymer of Mercury(II) with Schiff Base Ligands containing N3 and N4 Donors

Two dinuclear mercury(II) iodide compounds, [Hg₂(L)(I)₄] ( 1 ) and [(L′)Hg(μ‐I)₂HgI₂]_n ( 2 ) [L = N,N′‐bis(phenyl(pyridin‐2‐yl)methylene)propane‐1,2‐diamine and L′ = N‐(phenyl(pyridin‐2‐yl)methylene)propane‐1,2‐diamine] were synthesized and characterized. The molecular structures of [Hg₂(L)(I)₄] ( 1 ) and [(L′)Hg(μ‐I)₂HgI₂]_n ( 2 ), which were determined by single‐crystal X‐ray diffraction, indicate that each Hg^II in 1 has a distorted tetrahedral environment around the metal atom with a HgN₂I₂ chromophore, whereas in 2 one mercury(II) atom adopts a distorted tetrahedral arrangement with a HgI₄ chromophore and the other has a distorted square pyramidal environment with HgN₃I₂ chromophore. In the solid state, compound 2 consists of a 1D coordination polymer structure.     

Preparation and Crystal Structures of the Hydrous Mercury Tellurates,HgII(H4TeVIO6) and HgI2(H4TeVIO6)(H6TeVIO6)·2H2O

Single crystals of Hg^II(H₄Te^VIO₆) (colourless to light‐yellow, rectangular plates) and Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O (colourless, irregular) were grown from concentrated solutions of orthotelluric acid, H₆TeO₆, and respective solutions of Hg(NO₃)₂ and Hg₂(NO₃)₂. The crystal structures were solved and refined from single crystal diffractometer data sets (Hg^II(H₄Te^VIO₆): space group Pna2₁, Z = 4, a =10.5491(17), b = 6.0706(9), c = 8.0654(13)Å, 1430 structure factors, 87 parameters, R[F² > 2σ(F²)] = 0.0180; Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O: space group P1¯, Z = 1, a = 5.7522(6), b = 6.8941(10), c = 8.5785(10)Å, α = 90.394(8), β = 103.532(11), γ = 93.289(8)°, 2875 structure factors, 108 parameters, R[F² > 2σ(F²)] = 0.0184). The structure of Hg^II(H₄Te^VIO₆) is composed of ribbons parallel to the b axis which are built of [H₄TeO₆]^2— anions and Hg²⁺ cations held together by two short Hg—O bonds with a mean distance of 2.037Å. Interpolyhedral hydrogen bonding between neighbouring [H₄TeO₆]^2— groups, as well as longer Hg—O bonds between Hg atoms of one ribbon to O atoms of adjacent ribbons lead, to an additional stabilization of the framework structure. Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O is characterized by a distorted hexagonal array made up of [H₄TeO₆]^2— and [H₆TeO₆] octahedra which spread parallel to the bc plane. Interpolyhedral hydrogen bonding between both building units stabilizes this arrangement. Adjacent planes are stacked along the a axis and are connected by Hg₂²⁺ dumbbells (d(Hg—Hg) = 2.5043(4)Å) situated in‐between the planes. Additional stabilization of the three‐dimensional network is provided by extensive hydrogen bonding between interstitial water molecules and O and OH‐groups of the [H₄TeO₆]^2— and [H₆TeO₆] octahedra. Upon heating Hg^I₂(H₄Te^VIO₆)(H₆Te^VIO₆)·2H₂O decomposes into TeO₂ under formation of the intermediate phases Hg^II₃Te^VIO₆ and the mixed‐valent Hg^IITe^IV/VI₂O₆.     

Anion and Additive Effects on the Structure of Mercury(II) Halides Complexes with Tripodal Ligand

The metal complexes [Hg₂(tbim)₂Br₄]·2DMF ( 1 ) and [Hg₂(tbim)I₄]·1.5DMF ( 2 ) were prepared by reactions of 1,3,5‐tris(benzimidazol‐1‐ylmethyl)‐2,4,6‐trimethylbenzene (tbim) with HgBr₂, HgI₂, respectively, and [Hg₂(tbim)I₄]·0.5(FeCp₂)·H₂O ( 3 ) was obtained by the same method with addition of ferrocene (FeCp₂) as additive. Their structures were determined by X‐ray crystallographic analyses. Complex 1 has a macrocyclic binuclear structure with one benzimidazole arm of the ligand free of coordination and the binuclear units are further connected by C‐H···N hydrogen bonds to give an infinite zigzag chain. Complexes 2 and 3 have a 2D network structure in which tbim serves as a tridentate ligand. The results showed that the halides of bromide and iodide have remarkable impact on the structure of the complexes. The FeCp₂ molecules are trapped in the voids of framework 3 .     

Chemical Conversion of Hg‐Clusters: Synthesis and Crystal Structure of $ {\rm [(DMSO)_2 Co(NC \overline{S)_4(Hg}-TePh)_2]_{\rm n} }$, the First Compound Containing a Polymeric Hg—Te Chain

The six‐membered ring Hg₃Te₃ of [Hg₃Cl₃(μ‐TePh)₃]·2 DMSO {(Ph = C₆H₅; DMSO = (CH₃)₂SO} was opened by redissolution with DMSO, reacting with Co[Hg(SCN)₄] and affording polymeric . The monoclinic novel compound belong to the space group P2₁/n and assembles in a bidimensional lattice tetrahedral Hg^II(SCN)₂Te₂‐ and octahedral Co^II(NCS)₄(DMSO)₂‐chains linked trough SCN bridges along the crystallographic axis b and diagonally to the ac axes. The structure of [(DMSO)₂Co(NCS)₄(Hg—TePh)₂]_n is limited by the DMSO ligands in the axial positions of the Co‐octahedrons.     

Syntheses,Structures, and Theoretical Studies of New Mercury Iodobismuthates: (Et4N)4(Bi4Hg2I20) and (nBu4N)2(Bi2HgI10)

The first two mercury iodobismuthates, (Et₄N)₄(Bi₄Hg₂I₂₀) ( 1 ) and (nBu₄N)₂(Bi₂HgI₁₀) ( 2 ) have been synthesized by the reactions of binary BiI₃ and HgI₂ in a mixed solution of ethanol/acetone with the existence of different ammonia cations. The novel hexanuclear (Bi₄Hg₂I₂₀)^4– anion in 1 can be viewed as a dimer of the trinuclear (Bi₂HgI₁₀)^2– anion in 2 . The DFT calculations reveal that the band gaps of both compounds are determined only by the anionic moieties and therefore are similar, which agrees with the experimental measurements.     

Vaporization chemistry and thermodynamics in the CdGa2S4-Ga2S3 system

The chemistry and thermodynamics of vaporization of CdGa₂S₄(s), CdGa₈S₁₃(s), and Ga₂S₃(s) were studied by computer-automated, simultaneous Knudsen-effusion and torsion-effusion, vapor pressure measurements in the temperature range 967–1280 K. The vaporization was incongruent with loss of Cd(g) + 1/2 S₂(g) and production of CdGa₈S₁₃(s), a previously unknown compound, in equilibrium with CdGa₂S₄(s), until the solid became CdGa₈S₁₃ only. Then, incongruent vaporization continued with production of Ga₂S₃(s) until the solid was Ga₂S₃ only. The latter vaporized congruently. The ΔH°(298 K) of combination of one mole of CdS(s) with one mole of Ga₂S₃(s) to give CdGa₂S₄(s) was ?22.6 ± 0.9 kJ mole^?1. The 2H2(298 K) of combination of one mole of CdS(s) with four moles of Ga₂S₃(s) to give CdGa₈S₁₃(s) was ?25.5 ± 1.1 kJ mole^?1. The 2H2(298K) of CdGa₈S₁₃(s) with respect to disproportionation into CdGa₂S₄(s) and 3 Ga₂S₃(s) was ?2.8 ± 0.6 kJ mole^?1. CdGa₈S₁₃(s) was not observed at room temperature. The 2H2(298 K) of vaporization of the residual Ga₂S₃(s) was 663.4 ± 0.8 kJ mole^?1, which compared well with a value of 661.4 ± 0.3 kJ mole^?1 already available from the literature. Implications of small variations in stoichiometry of compounds in this study were observed and are discussed.     

Kinetics of HD exchange in the reaction of HBF2 with D2

The rate constant for the unusually rapid HD exchange reaction of D₂ with HBF₂ : D₂(g) + HBF₂(g) → DBF₂(g) + HD(g) has been measured (k₂(298K) = (7.42 ± 2.0) × 10^?23 cm³/molecule s). The activation energy for this reaction has been estimated to be 17.8 ± 1.2 kcal/mole. The mechanism probably involves a multicenter orbital interaction between D₂ and HBF₂.     

Knudsen measurements of the sublimation and the heat of formation of GeSe2 [1]

Knudsen effusion studies of the sublimation of polycrystalline GeSe₂ have been performed employing mass spectrometry in a temperature range of about 610–750 K and vacuum microbalance techniques in the temperature range 614–801 K and at pressures ranging from about 10^?7 ? 10^?4 atm. The results demonstrate that GeSe₂ vaporizes congruently under present experimental conditions according to the predominant reaction (1) GeSe₂(s) = GeSe(g) + 1/2 Se₂(g) and a minor reaction (2) GeSe₂(s) = GeSe₂(g). The mean values for the third law heat and second law entropy of reaction (1) based on direct mass-loss data are ΔH°₂₉₈ = 70.4 ± 2 kcal/mole and ΔS°₂₉₈ = 64.7 ± 2 eu. From these the standard heat of formation and absolute entropy of GeSe₂(s) were calculated to be ?21.7 ± 2 kcal/mole and 24.6 ± 2 eu, respectively.     

Zur thermischen Zersetzung und Sublimation des NiI2

Thermical Decomposition and Sublimation of NiI₂ In a membran manometer the thermical decomposition and the sublimation of NiI₂ was measured and in ampuls the sublimation of NiI₂ studied. From the total pressure and the sublimation pressure the enthalpy of formation ΔH°(f,NiI₂,f,298) = ?20 ± 2 kcal/mole and ΔH°(f,NiI₂,g,298) = +31.2 ± 5 kcal/mole was derived. The entropy dates are: S°(NiI₂,f,298) = 35 ± 2 cl, S°(NiI₂,g,298) = 80 ± 1 cl and S°(Ni₂I₄,g,298) = 128 ± 3 cl respectively. The Ni formed with NiI₂ an eutectical system.     

Quecksilber(II)‐chlorid‐ und ‐iodid‐Komplexe von Dithia‐ und Tetrathiakronenethern

Mercury(II) Chloride and Iodide Complexes of Dithia‐ and Tetrathiacrown Ethers The complexes [(HgCl₂)₂((ch)₂30S₄O₆)] ( 1 ), [HgCl₂(mn21S₂O₅)] ( 2 ), [HgCl₂(ch18S₂O₄)] ( 3 ) and [HgI(meb12S₂O₂)]₂[Hg₂I₆] ( 4 ) have been synthesized, characterized and their crystal structures were determined. In [(HgCl₂)₂((ch)₂30S₄O₆)] two HgCl₂ units are discretely bonded within the ligand cavity of the 30‐membered dichinoxaline‐tetrathia‐30‐crown‐10 ((ch)₂30S₄O₆) forming a binuclear complex. HgCl₂ forms 1 : 1 “in‐cavity” complexes with the 21‐membered maleonitrile‐dithia‐21‐crown‐7 (mn21S₂O₅) ligand and the 18‐membered chinoxaline‐dithia‐18‐crown‐6 (ch18S₂O₄) ligand, respectively. The 12‐membered 4‐methyl‐benzo‐dithia‐12‐crown‐4 (meb12S₂O₂) ligand gave with two equivalents HgI₂ the compound [HgI(meb12S₂O₂)]₂[Hg₂I₆]. In the cation [HgI(meb12S₂O₂)]⁺ meb12S₂O₂ forms with the cation HgI⁺ a half‐sandwich complex.     

Synthesis,Structure and Characterization of Two Novel Mercury(II) Complexes with N‐(2‐aminoethyl)piperazine

Two novel mercury(II) complexes [Hg^II(μ₂‐LH)Cl₂]₂[Hg^II₂(μ₂‐Cl)₂Cl₄]·2H₂O ( 1 ) and [Hg^II₄(μ₂‐L)₂(μ₂‐Cl)₂Cl₆] ( 2 ) have been synthesized by the reaction of N‐(2‐aminoethyl)piperazine (L) with HgCl₂ under different pH conditions. 1 and 2 were characterized by single‐crystal X‐ray diffraction analysis. The results reveal that in 1 there exist discrete mononuclear [Hg^II(μ₂‐LH)Cl₂]⁺ units and binuclear [Hg^II₂(μ₂‐Cl)₂Cl₄]²⁺ unit while in 2 there exist the rarely reported discrete cylic tetranuclear [Hg^II₄(μ₃‐L)₂(μ₂‐Cl)₂Cl₆] cluster units, which are both assembled into 3D supramolecular structures via extensive hydrogen‐bonding interactions. 1 and 2 were also characterized by element analysis, FT‐IR and luminescence spectra.     

The kinetics and equilibrium of the gas-phase reaction CH3CF2Br + I2 = CH3CF2I + IBr the C-Br bond dissociation energy in 1,1-difluorobromoethane

The kinetics and equilibrium of the gas-phase reaction of CH₃CF₂Br with I₂ were studied spectrophotometrically from 581 to 662°K and determined to be consistent with the following mechanism: A least squares analysis of the kinetic data taken in the initial stages of reaction resulted in log k₁ (M^?1 · sec^?1) = (11.0 ± 0.3) - (27.7 ± 0.8)/θ where θ = 2.303 RT kcal/mol. The error represents one standard deviation. The equilibrium data were subjected to a “third-law” analysis using entropies and heat capacities estimated from group additivity to derive ΔH_r° (623°K) = 10.3 ± 0.2 kcal/mol and ΔH_rr (298°K) = 10.2 ± 0.2 kcal/mol. The enthalpy change at 298°K was combined with relevant bond dissociation energies to yield DH°(CH₃CF₂ - Br) = 68.6 ± 1 kcal/mol which is in excellent agreement with the kinetic data assuming that E₂ = 0 ± 1 kcal/mol, namely; DH°(CH₃CF₂ - Br) = 68.6 ± 1.3 kcal/mol. These data also lead to ΔH_f°(CH₃CF₂Br, g, 298°K) = -119.7 ± 1.5 kcal/mol.     

Sättigungsdrucke,Bildungsenthalpien von WOBr4 und WO2Br2, die Reaktionsgleichgewichte 2WO2Br2 = WO3 + WOBr4 und 2WOBr4 + SiO2 = 2WO2Br2 + SiBr4

The saturation vapour pressures of WOBr₄ and WO₂Br₂ and their reaction equilibria have been determined by means of a membrane zero manometer and ampoule quenching experiments, respectively. From the pressuretemperature dependence the following sublimation data were estimated: Δ H° (subl., WOBr₄, 298) = 29.4 (± 1.0) kcal/mole; Δ H° (subl., WO₂Br₂, 298) = 36.6 (±1.5) kcal/mole; Δ S° (subl., WOBr₄, 298) = 50.1 (± 1) cl; Δ S° (subl. WO₂Br₂, 298) = 53.0 (±1.5) cl. For the decomposition reaction of solid WO₂Br₂ were obtained: Δ H° (s, 690) 37.5 (± 0.7) kcal/mole, Δ S° (s, 690) = 49.0 (± 0.5) cl; and for the decomposition of gaseous WO₂Br₂: Δ H° (g, 690) = ?29.6 (± 2.0) kcal/mole, Δ S°. (g, 690) = ?44.5 (± 1.5) cl.     

Structural and Coordinative Variability in Zinc(II), Cadmium(II), and Mercury(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Sodium in dry methanol reduces 2‐cyanopyridine in the presence of 3‐hexamethyleneiminylthiosemicarbazide and produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim ( 1 ). Complexes with zinc(II ), cadmium(II ) and mercury(II ) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of HAmhexim ( 1 ), [Zn(Amhexim)(OAc)]₂μ·μDMSO ( 2 ), [Cd(HAmhexim)Cl₂]μ·μDMSO ( 7 ), [Cd(Amhexim)₂] ( 8 ), [Cd(HAmhexim)Br₂]μ·μDMSO ( 9 ), [Cd(HAmhexim)I₂]μ·μEtOH ( 10 ), [Hg(HAmhexim)Cl₂]μ·μDMSO ( 11 ), [Hg(Amhexim)Br]₂ ( 13 ), [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O ( 14 ) and [Hg(Amhexim)I]₂ ( 15 ) have been determined. Coordination of the anionic and neutral thiosemicarbazone ligand occurs through the pyridine nitrogen atom, imine nitrogen atom, and thiolato or thione sulfur atom. In [Zn(Amhexim)(OAc)]₂ one of the bridging acetato ligands has monodentate coordination and the other bridges in a bidentate manner. [Cd(Amhexim)₂] is a 6‐coordinate species while the other cadmium complexes are 5‐coordinate. In [Hg(Amhexim)Br]₂ and [Hg(Amhexim)I]₂ the thiolato sulfur atoms act as bridges between the Hg atoms to form dimeric compounds and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O is a trinuclear complex with three different centers — two metallic centers have a 5‐coordination and the another one has 4‐coordination. In addition, [Hg(HAmhexim)Cl₂]μ·μDMSO and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O shown a supramolecular one‐dimensional hydrogen‐bonded self‐assembling.     

ab initio calculations and thermochemical analysis on C1 atom abstractions of chlorine from chlorocarbons and the reverse alkyl abstractions: Cl2 + R· ↔ Cl· + RCl

Thermodynamic properties (ΔH°_f(298), S°₍₂₉₈₎ and Cp(T) from 300 to 1500 K) for reactants, adducts, transition states, and products in reactions of CH₃ and C₂H₅ with Cl₂ are calculated using CBSQ//MP2/6‐311G(d,p). Molecular structures and vibration frequencies are determined at the MP2/6‐311G(d,p), with single‐point calculations for energy at QCISD(T)/6‐311 + G(d,p), MP4(SDQ)/CbsB4, and MP2/CBSB3 levels of calculation with scaled vibration frequencies. Contributions of rotational frequencies for S°₍₂₉₈₎ and Cp(T)'s are calculated based on rotational barrier heights and moments of inertia using the method of Pitzer and Gwinn [1]. Thermodynamic parameters, ΔH°_f(298), S°₍₂₉₈₎, and C_P(T), are evaluated for C₁ and C₂ chlorocarbon molecules and radicals. These thermodynamic properties are used in evaluation and comparison of Cl₂ + R· → Cl· + RCl (defined forward direction) reaction rate constants from the kinetics literature for comparison with the calculations. Data from some 20 reactions in the literature show linearity on a plot of Ea_fwd vs. ΔH_rxn,fwd, yielding a slope of (0.38 ± 0.04) and intercept of (10.12 ± 0.81) kcal/mole. A correlation of average Arrhenius preexponential factor for Cl· + RCl → Cl₂ + R· (reverse rxn) of (4.44 ± 1.58) × 10¹³ cm³/mol‐sec on a per‐chlorine basis is obtained with Ea_Rev = (0.64 ± 0.04) × ΔH_rxn,Rev + (9.72 ± 0.83) kcal/mole, where Ea_Rev is 0.0 if ΔH_rxn,Rev is more than 15.2 kcal/mole exothermic. Kinetic evaluations of literature data are also performed for classes of reactions. Ea_fwd = (0.39 ± 0.11) × ΔH_rxn,fwd + (10.49 ± 2.21) kcal/mole and average A_fwd = (5.89 ± 2.48) × 10¹² cm³/mole‐sec for hydrocarbons: Ea_fwd = (0.40 ± 0.07) × ΔH_rxn,fwd + (10.32 ± 1.31) kcal/mole and average A_fwd = (6.89 ± 2.15) × 10¹¹ cm³/mole‐sec for C₁ chlorocarbons: Ea_fwd = (0.33 ± 0.08) × ΔH_rxn,fwd + (9.46 ± 1.35) kcal/mole and average A_fwd = (4.64 ± 2.10) × 10¹¹ cm³/mole‐sec for C₂ chlorocarbons. Calculation results on the methyl and ethyl reactions with Cl₂ show agreement with the experimental data after an adjustment of +2.3 kcal/mole is made in the calculated negative Ea's. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 548–565, 2000