Gas‐phase basicity of 2‐furaldehyde

2‐Furaldehyde (2‐FA), also known as furfural or 2‐furancarboxaldehyde, is an heterocyclic aldehyde that can be obtained from the thermal dehydration of pentose monosaccharides. This molecule can be considered as an important sustainable intermediate for the preparation of a great variety of chemicals, pharmaceuticals and furan‐based polymers. Despite the great importance of this molecule, its gas‐phase basicity (GB) has never been measured. In this work, the GB of 2‐FA was determined by the extended Cooks's kinetic method from electrospray ionization triple quadrupole tandem mass spectrometric experiments along with theoretical calculations. As expected, computational results identify the aldehydic oxygen atom of 2‐FA as the preferred protonation site. The geometries of O‐O‐cis and O‐O‐trans 2‐FA and of their six different protomers were calculated at the B3LYP/aug‐TZV(d,p) level of theory; proton affinity (PA) values were also calculated at the G3(MP2, CCSD(T)) level of theory. The experimental PA was estimated to be 847.9 ± 3.8 kJ mol^?1, the protonation entropy 115.1 ± 5.03 J mol^?1 K^?1 and the GB 813.6 ± 4.08 kJ mol^?1 at 298 K. From the PA value, a ΔH°_f of 533.0 ± 12.4 kJ mol^?1 for protonated 2‐FA was derived. Copyright © 2012 John Wiley & Sons, Ltd.     

Mechanistic Aspects of Ligand Substitution on the Hydroxopentaaquarhodium(III) Ion in Aqueous Solution by Sulfur‐Containing Bioactive Ligands

The kinetics of the interactions between three sulfur‐containing ligands, thioglycolic acid, 2‐thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two‐step process in which the first step is ligand‐dependent and the second step is ligand‐independent chelation. Rate constants (k₁ ～10^?3 s^?1 and k₂ ～10^?5 s^?1) and activation parameters (for thioglycolic acid: ΔH₁^≠ = 22.4 ± 3.0 kJ mol^?1, ΔS₁^≠ = ?220 ± 11 J K^?1 mol^?1, ΔH₂^≠ = 38.5 ± 1.3 kJ mol^?1, ΔS₂^≠ = ?204 ± 4 J K^?1 mol^?1; for 2‐thiouracil: ΔH₁^≠ = 42.2 ± 2.0 kJ mol^?1, ΔS₁^≠ = ?169 ± 6 J K^?1 mol^?1, ΔH₂^≠ = 66.1 ± 0.5 kJ mol^?1, ΔS₂^≠ = ?124 ± 2 J K^?1 mol^?1; for glutathione: ΔH₁^≠ = 47.2 ± 1.7 kJ mol^?1, ΔS₁^≠ = ?155 ± 5 J K^?1mol^?1, ΔH₂^≠ = 73.5 ± 1.1 kJ mol^?1, ΔS₂^≠ = ?105 ± 3 J K^?1 mol^?1) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis. A rate law involving the outer sphere association complex formation has been established as      

Proton affinities by reactant ion monitoring: Triphenyl group Va compounds

Proton affinities of a series of triphenyl Group Va compounds have been determined by bracketing using reactant ion monitoring: (C₆H₅)₃N = 904 ± 8 kJ mol^?1, (C₆H₅)₃P = 968 ± 5 kJ mol^?1, (C₆H₅)₃As = 904 ± 8 kJ mol^?1 and (C₆H₅)₃Sb = 846 ± 8 kJ mol^?1. The large difference in substituent effect of phenyl for hydrogen between As or P and N may result from overlap of the 2p orbitals of N with the sp² orbitals on the ring carbons and lack of overlap for P or As. Proton affinities of phenylalkylphosphine oxides are essentially the same, 904 ± 8 kJ mol^?1, independent of alkyl group.     

Heat of formation for the propanoyl cation by photoionization mass spectrometry

The ionization energies and [C₃H₅O]⁺ appearance energies for a series of oxygenated organic compounds have been measured by dissociative photoionization mass spectrometry. The adiabatic ionization energy for cyclopentanol is observed to be 9.72 eV. A 298 K heat of formation of 591.2±2.3kJ mol^?1, based on the stationary electron convention, is derived for the propanoyl cation in the gas phase. A heat of formation of –86±6 kJ mol^?1 is obtained for methylketene, which leads to an absolute proton affinity of 853±8 kJ mol^?1.     

Equilibrium and Kinetic Studies on Ligand Substitution Reactions of Trans-[COIII(en)2(Me)H2O]2+: A Model for Coenzyme B12

Ligand substitution of trans-[Co^III(en)₂(Me)H₂O]²⁺ was studied for pyrazole, 1,2,4-triazole and N-acetylimidazole as entering nucleophiles. These displace the coordinated H₂O molecule trans to the methyl group to form trans-[Co(en)₂(Me)azole]. Stability constants at 18°C for the substitution of H₂O by pyrazole, 1,2,4-triazole and N-acetylimidazole are 0.7 ± 0.1, 13.8 ± 1.4 and 1.7 ± 0.2 M^?1, respectively. Second order rate constants at the same temperature for the reaction of trans-[Co^III(en)₂(Me)H₂O]²⁺ with pyrazole, 1,2,4-triazole and N-acetylimidazole are 161 ± 12, 212 ± 11 and 12.9 ± 1.6 M^?1 s^?1, respectively. Activation parameters (ΔH^≠, ΔS^≠) are 67 ± 6 kJ mol^?1, + 27 ± 19 J K^?1 mol^?1; 59 ± 2 kJ mol^?1, + 1 ± 6 J K^?1 mol^?1 and 72 ± 4 kJ mol^?1, + 23 ± 14 J K^?1 mol^?1 for reactions with pyrazole, 1,2,4-triazole and N-acetylimidazole, respectively. Substitution of coordinated H₂O by azoles follows an I_d mechanism.     

Experimental and theoretical studies of the basicity and proton affinity of SiF4 and the structure of SiF4H+

A combined experimental and theoretical approach has been employed to establish the basicity and proton affinity of SiF₄ and the structure of SiF₄H⁺. The kinetics and energetics for the transfer of a proton between SiF₄, N₂, and Xe have been explored experimentally in helium at 0.35±0.02 torr and 297±3 K with a selected-ion flow tube apparatus. The results of equilibrium constant measurements are reported that provide a basicity and proton affinity for SiF₄ at 297±3 K of 111.4±1.0 and 117.7±1.2 kcal mol^?1, respectively. These values are more than 2.5 kcal mol^?1 lower than currently recommended values. The basicity order was determined to be GB(Xe)>GB(SiF₄)>GB(N₂), while the proton-affinity order was shown to be PA(Xe)>PA(N₂)>PA (SiF₄). Ab initio molecular orbital computations at MP4SDTQ(fc)/6-311++G(3df,3pd) using geometries from B3LYP/6-31+G(d,p) indicate a value for PA(SiF₄)=118.7 kcal mol^?1 that is in good agreement with experiment. Also, the most stable structure of SiF₄H⁺ is shown to correspond to a core SiF ₃ ⁺ cation solvated by HF with a binding energy of 43. 9 kcal mol^?1. Support for this structure is found in separate SIFT collision induced dissociation (CID) measurements that indicate exclusive loss of HF.     

The standard enthalpies of formation of cyclohexylamine and cyclohexylamine hydrochloride

The standard enthalpy of combustion of cyclohexylamine has been measured in an aneroid rotating-bomb calorimeter. The value ΔH_o^o(c-C₆H₁₁NH₂, 1) = ?(4071.3 ± 1.3) kJ mol^?1 yields the standard enthalpy of formation ΔH_f^o(c-C₆H₁₁NH₂, 1) = ?(147.7 ± 1.3) kJ mol^?1. The corresponding gas-phase standard enthalpy of formation for cyclohexylamine is ΔH_f^o(c-C₆H₁₁NH₂, g) = ?(104.9 ± 1.3) kJ mol^?1. The standard enthalpy of formation of cyclohexylamine hydrochloride, ΔH_f^o(c-C₆H₁₁NH₂·HCl, c) = ?(408.2 ± 1.5) kJ mol^?1, was derived by combining the measured enthalpy of solution of the salt in water, literature data, and the ΔH_c^o measured in this study. Comment is made on the thermochemical bond enthalpy H(CN).     

Two Three‐Dimensional Metal‐Organic Frameworks Constructed from Alkaline Earth Metal Cations (Sr and Ba) and 5‐Nitroisophthalicacid – Synthesis,Charaterization, and Thermochemistry

Two MOFs of [Sr^II(5‐NO₂‐BDC)(H₂O)₆] ( 1 ) and [Ba^II(5‐NO₂‐BDC)(H₂O)₆] ( 2 ) have been synthesized in water using alkaline earth metal salts and the rigid organic ligand 5‐NO₂‐H₂BDC. The compounds were characterized by elemental analysis, infrared spectrum, thermal analysis, and X‐ray crystallography. Crystal structure analyses have shown that the two complexes are isostructural as evidenced by IR spectra and TG‐DTA. Both compounds present three‐dimensional frameworks built up from infinite chains of edge‐sharing twelve‐membered rings through O–H···O hydrogen bonds. The specific heat capacities of the title complexes have been determined by an improved RD496‐III microcalorimeter with the values of (109.29 ± 0.693) J mol⁻¹ K⁻¹ and (81.162 ± 0.858) J mol⁻¹ K⁻¹ at 298.15 K, and the molar enthalpy changes of the formation reactions of complexes at 298.15 K were calculated as (4.897 ± 0.008) kJ mol⁻¹ and (2.617 ± 0.009) kJ mol⁻¹, respectively.     

Experimental and theoretical study of the homogeneous,unimolecular gas‐phase elimination kinetics of 2‐furoic acid

The kinetics of the gas‐phase elimination kinetics of CO₂ from furoic acid was determined in a static system over the temperature range 415–455°C and pressure range 20–50 Torr. The products are furan and carbon dioxide. The reaction, which is carried out in vessels seasoned with allyl bromide and in the presence of the free‐radical suppressor toluene and/or propene, is homogeneous, unimolecular, and follows a first‐order rate law. The observed rate coefficient is expressed by the following Arrhenius equation: log k₁(s^?1) = (13.28 ± 0.16) ? (220.5 ± 2.1) kJ mol^?1 (2.303 RT)^?1. Theoretical studies carried out at the B3LYP/6‐31++G** computational level suggest two possible mechanisms according to the kinetics and thermodynamic parameters calculated compared with experimental values. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 298–306, 2007     

Proton and sodium ion affinities of glycine and its sodium salt in the gas phase. Ab initio calculations

The energies of protonation and Na⁺ cationization of glycine (GLY) and its (GLY ? H + Na) salt in the gas phase were calculated using ab inltio calculations. The proton affinity of GLY, valued at the MP2/6–31G*//3-21G level, is 937 kJ mol^?1. The amino function is confirmed to be the most favourable site of protonation: ‘proton affinities’ of the carbonyl and hydroxyl functions are calculated to be 75 and 180 kJ mol^?1, respectively, lower than that of NH₂ at the MP2/6-31G*//3–21G level. Calculations performed up to the MP2/6–31G*//3–21G level give the Na⁺ affinity of GLY as 189 kJ mol^?1 and the H⁺ and Na⁺ affinities of (GLY – H + Na) as 1079 and 298 kJ mol^?1, respectively. The geometries of all neutral and protonated species optimized with the 3–21G basis set are described. Both H* and Na⁺ cations complex preferably between the nitrogen atom and the carbonyl oxygen atom, leading to pseudo-five-membered ring structures in which Na? O and Na? N bonds lengths are greater than 2 Å.     

Fourier transform-ion cyclotron resonance study of the gas-phase acidities of germane and methylgermane; Bond dissociation energy of germane

An accurate gas-phase acidity for germane (enthalpy scale, equivalent to the proton affinity of GeH₃ ^?), ΔH _acid ^o(GeH₄) = 1502.0 ± 5.1 kJ mol^?1, is obtained by constructing a consistent acidity ladder between GeH₄, and H₂S by using Fourier transform-ion cyclotron resonance spectrometry, and 0 and 298.15 K values for the first bond dissociation energy of GeH₄ are proposed: D₀ ^o(H₃Ge-H) = 352 ± 9 kJ mol^?1; D ^o(H₃Ge-H) = 358 ± 9 kJ mol^?1, respectively. These results are compared with experimental and theoretical data reported in the literature. Methylgermane was found to be a weaker acid than germane by approximately 35 kJ mol^?1: ΔH _acid ^o = 1536.6 kJ mol^?1.     

The elimination kinetics and mechanisms of ethyl piperidine‐3‐carboxylate,ethyl 1‐methylpiperidine‐3‐carboxylate,and ethyl 3‐(piperidin‐1‐yl)propionate in the gas phase

The gas‐phase elimination kinetics of the above‐mentioned compounds were determined in a static reaction system over the temperature range of 369–450.3°C and pressure range of 29–103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3‐(piperidin‐1‐yl) propionate, log k₁(s^?1) = (12.79 ± 0.16) ? (199.7 ± 2.0) kJ mol^?1 (2.303 RT)^?1; ethyl 1‐methylpiperidine‐3‐carboxylate, log k₁(s^?1) = (13.07 ± 0.12)–(212.8 ± 1.6) kJ mol^?1 (2.303 RT)^?1; ethyl piperidine‐3‐carboxylate, log k₁(s^?1) = (13.12 ± 0.13) ? (210.4 ± 1.7) kJ mol^?1 (2.303 RT)^?1; and 3‐piperidine carboxylic acid, log k₁(s^?1) = (14.24 ± 0.17) ? (234.4 ± 2.2) kJ mol^?1 (2.303 RT)^?1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six‐membered cyclic transition state type of mechanism. The intermediate β‐amino acids decarboxylate as the α‐amino acids but in terms of a semipolar six‐membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106–114, 2006     

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

Alkali niobates and tantalates are currently important lead‐free functional oxides. The formation and decomposition energetics of potassium tantalum oxide compounds (K₂O?Ta₂O₅) were measured by high‐temperature oxide melt solution calorimetry. The enthalpies of formation from oxides of KTaO₃ perovskite and defect pyrochlores with K/Ta ratio of less than 1 stoichiometry—K_0.873Ta_2.226O₆, K_1.128Ta_2.175O₆, and K_1.291Ta_2.142O₆—were experimentally determined, and the values are (?203.63±2.92) kJ mol^?1 for KTaO₃ perovskite, and (?339.54±5.03) kJ mol^?1, (?369.71±4.84) kJ mol^?1, and (?364.78±4.24) kJ mol^?1, respectively, for non‐stoichiometric pyrochlores. That of stoichiometric defect K₂Ta₂O₆ pyrochlore, by extrapolation, is (?409.87±6.89) kJ mol^?1. Thus, the enthalpy of the stoichiometric pyrochlore and perovskite at K/Ta=1 stoichiometry are equal in energy within experimental error. By providing data on the thermodynamic stability of each phase, this work supplies knowledge on the phase‐formation process and phase stability within the K₂O?Ta₂O₅ system, thus assisting in the synthesis of materials with reproducible properties based on controlled processing. Additionally, the relation of stoichiometric and non‐stoichiometric pyrochlore with perovskite structure in potassium tantalum oxide system is discussed.     

Low temperature 13C NMR study of 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkyl- aminocyclohexanes

Cyclohexane and piperidine ring reversal in 1-(3-pentyloxyphenylcarbamoyloxy)-2-dialkylaminocyclohexanes was investigated by ¹³C NMR. An unusually low conformational energy ΔG = 0.59 kJ mol^?1 and activation parameters ΔG^≠₂₁₈ = 43.8 ± 0.4 kJ mol^?1, ΔH^≠ = 48.9 ± 2.5 kJ mol^?1 and ΔS^≠ = 23 ± 9 J mol^?1 K^?1 were found for the diequatorial to diaxial transition of the cyclohexane ring in the trans-pyrrolidinyl derivative. In the trans-piperidinyl derivative, ΔG₂₂₂ = 44.7 ± 0.5 KJ mol^?1, ΔH^≠ = 55.7 ± 6.3 kJ mol^?1 and ΔS^≠ = 51 ± 21 J mol^?1 K^?1 was found for the piperidine ring reversal from the non-equivalence of the α-carbons.     

A Phosphorus Bisylide: Exploring a New Class of Superbases with Two Interacting Carbon Atoms as Basicity Centers

Herein we present the first superbase MHPN with two interacting P‐ylide entities. Unlike classical proton sponges, this novel compound class has carbon atoms as basicity centers which are forced into close proximity by a naphthalene scaffold. The bisylide exhibits an experimental pK _BH⁺ value of 33.3±0.2 on the MeCN scale and a calculated gas‐phase proton affinity of 277.9 kcal mol⁻¹ (M062X/6‐311+G**//M062X/6‐31G*+ZPVE method) exceeding that of the corresponding monoylide by nearly 15 kcal mol⁻¹. The origin of the unexpectedly high basicity of the new bisylide was investigated by NMR spectroscopic methods, single‐crystal X‐ray diffraction as well as theoretical calculations and can be partly attributed to the rapid exchange of the “acidic” proton between the two basic carbon atoms after protonation.     

Steric and electronic contributions to barriers of internal rotation in 1,8-dibenzoylnaphthalenes

Restricted rotation about the naphthalenylcarbonyl bonds in the title compounds resulted in mixtures of cis and trans rotamers, the equilibrium and the rotational barriers depending on the substituents. For 2,7-dimethyl-1,8-di-(p-toluoyl)-naphthalene (1) ΔH° = 3.66 ± 0.14 kJ mol^?1, ΔS° = 1.67 ± 0.63 J mol^?1 K^?1, ΔH^≠_ct = 55.5 ± 1.3 kJ mol^?1, ΔH^≠_ct = 51.9 ± 1.3 kJ mol^?1, ΔS^≠_ct = ?41.3±4.1 J mol^?1 K^?1 and ΔS^≠_ct = ?42.9±4.1 J mol^?1 K^?1. The rotation about the phenylcarbonyl bond requires ΔH^≠ = ?56.9±4.4 kJ mol^?1 and ΔS^≠ = ?20.5±15.3 J mol^?1 K^?1 for the cis rotamer, and ΔH^≠ = 43.5Δ0.4 kJ mol^?1 and ΔS^≠ =± ?22.4Δ1.3 J mol^?1 K^?1 for the trans rotamer. The role of electronic factors is likely to be virtually the same for both these rotamers but steric interaction between the two phenyl rings occurs in the cis rotamer only. Hence, the difference of the activation enthalpies obtained for the cis and trans rotamers, ΔΔH^?1 = 13.4 kJ mol^?1, provides a basis for the estimation of the role of steric factors in this rotation. For the tetracarboxylic acid 2 and its tetramethyl ester 3 the equilibrium is even more shifted towards the trans form because of enhanced steric and electrostatic interactions between the substituents in the cis form. The barriers for the rotation around the phenylcarbonyl bond and the cis-trans isomerization are lowered; an explanation for this result is presented.     

MP2, DFT‐D,and PCM study of the HMB–TCNE complex: Thermodynamics,electric properties,and solvent effects

Geometry, thermodynamic, and electric properties of the π‐EDA complex between hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) are investigated at the MP2/6‐31G* and, partly, DFT‐D/6‐31G* levels. Solvent effects on the properties are evaluated using the PCM model. Fully optimized HMB–TCNE geometry in gas phase is a stacking complex with an interplanar distance 2.87 × 10^?10 m and the corresponding BSSE corrected interaction energy is ?51.3 kJ mol^?1. As expected, the interplanar distance is much shorter in comparison with HF and DFT results. However the crystal structures of both (HMB)₂–TCNE and HMB–TCNE complexes have interplanar distances somewhat larger (3.18 and 3.28 × 10^?10 m, respectively) than our MP2 gas phase value. Our estimate of the distance in CCl₄ on the basis of PCM solvent effect study is also larger (3.06–3.16 × 10^?10 m). The calculated enthalpy, entropy, Gibbs energy, and equilibrium constant of HMB–TCNE complex formation in gas phase are: ΔH⁰ = ?61.59 kJ mol^?1, ΔS = ?143 J mol^?1 K^?1, ΔG⁰ = ?18.97 kJ mol^?1, and K = 2,100 dm³ mol^?1. Experimental data, however, measured in CCl₄ are significantly lower: ΔH⁰ = ?34 kJ mol^?1, ΔS = ?70.4 J mol^?1 K^?1, ΔG⁰ = ?13.01 kJ mol^?1, and K = 190 dm³ mol^?1. The differences are caused by solvation effects which stabilize more the isolated components than the complex. The total solvent destabilization of Gibbs energy of the complex relatively to that of components is equal to 5.9 kJ mol^?1 which is very close to our PCM value 6.5 kJ mol^?1. MP2/6‐31G* dipole moment and polarizabilities are in reasonable agreement with experiment (3.56 D versus 2.8 D for dipole moment). The difference here is due to solvent effect which enlarges interplanar distance and thus decreases dipole moment value. The MP2/6‐31G* study supplemented by DFT‐D parameterization for enthalpy calculation, and by the PCM approach to include solvent effect seems to be proper tools to elucidate the properties of π‐EDA complexes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

A kinetic study of the oxidation of L-ascorbic acid by chromium(VI)

The reaction between chromium(VI) and L-ascorbic acid has been studied by spectrophotometry in the presence of aqueous citrate buffers in the pH range 5.69–7.21. The reaction is slowed down by an increase of the ionic strength. At constant ionic strength, manganese(II) ion does not exert any appreciable inhibition effect on the reaction rate. The rate law found is where K_p is the equilibrium constant for protonation of chromate ion and k_r is the rate constant for the redox reaction between the active forms of the oxidant (hydrogenchromate ion) and the reductant (L-hydrogenascorbate ion). The activation parameters associated with rate constant k_r are E_a = 20.4 ± 0.9 kJ mol^?1, ΔH^≠ = 17.9 ± 0.9 kJ mol^?1, and ΔS^≠=?152 ± 3 J K^?1 mol^?1. The reaction thermodynamic magnitudes associated with equilibrium constant K_p are ΔH⁰ = 16.5 ± 1.1 kJ mol^?1 and ΔS⁰ = 167 ± 4 J K^?1 mol^?1. A mechanism in accordance with the experimental data is proposed for the reaction. © 1993 John Wiley & Sons, Inc.     

Enthalpy of formation and bond energies on unsaturated oxygenated hydrocarbons using G3MP2B3 calculation methods

Enthalpies of unsaturated oxygenated hydrocarbons and radicals corresponding to the loss of hydrogen atoms from the parent molecules are intermediates and decomposition products in the oxidation and combustion of aromatic and polyaromatic species. Enthalpies (Δ_fH⁰₂₉₈) are calculated for a set of 27 oxygenated and nonoxygenated, unsaturated hydrocarbons and 12 radicals at the G3MP2B3 level of theory and with the commonly used B3LYP/6‐311g(d,p) density functional theory (DFT) method. Standard enthalpies of formation (Δ_fH⁰₂₉₈) are determined from the calculated enthalpy of reaction (ΔH⁰_rxn,298) using isodesmic work reactions with reference species that have accurately known Δ_fH⁰₂₉₈ values. The deviation between G3MP2B3 and B3LYP methods is under ±0.5 kcal mol^?1 for 9 species, 18 other species differs by less than ±1 kcal mol^?1 , and 11 species differ by about 1.5 kcal mol^?1. Under them are 11 radicals derived from the above‐oxygenated hydrocarbons that show good agreement between G3MP2B3 and B3LYP methods. G3 calculations have been performed to further validate enthalpy values, where a discrepancy of more than 2.5 kcal mol^?1 exists between the G3MP3B3 and density functional results. Surprisingly the G3 calculations support the density functional calculations in these several nonagreement cases. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 633–648, 2005     

The platinumcarbon bond strength in Pt(PPh3)2(CH3)I

The enthalpies of reaction 1–3 have been determined

as ΔH(1) = ?176.6 ± 5.4, ΔH(2) = ?107.8 ± 6.0, and ΔH(3) = ?78.9 ± 2.0 kJ mol^?1. The bond dissociation energy difference D₁(PtCH₃) ? D₁(PtI) = +6 ± 5 kJ mol^?1 is calculated, which indicates that the two bonds have very similar strengths.