F:Flammable;
74-88-4Relevant articles and documents
Estimate of the iodine-iodine two-center three-electron bond energy in [CH3-I-I-CH3]+
Livant, Peter,Illies, Andreas
, p. 1510 - 1513 (1991)
The gas-phase ion-molecule association reaction CH3I+ + CH3I ? [CH3-I-I-CH3]+ in various bath gases was studied at 503 K. The iodine-iodine bond in the association product is an example of a two-center three-electron (2c-3e) or a 2σ/1σ* bond. The bond energy was estimated from ΔG° of reaction, which was in turn determined from equilibrium experiments. Assuming a value for ΔS° of reaction of -20 to -25 cal/(mol K), a bond strength of 23-26 kcal/mol is estimated. This is the first experimental gas-phase binding energy estimate for a 2c-3e bond in an organic molecule involving an iodine-iodine interaction and one of only a few experimental studies of well-characterized gas-phase 2c-3e bonding interactions between heteroatoms in organic molecules. A study of the ion-molecule reactions occurring at low ionizing energies leading to (CH3)2I+, [C2H3I2]+, and [CH3-I-I-CH3]+ is discussed.
Characterization and oxidative addition reactions for iridium cod complexes
Purcell,Conradie,Kumar,Venter
, p. 10 - 24 (2017)
Three different [Ir(LL′)(cod)] complexes (LL′?=?N-aryl-N-nitrosohydroxylaminato) (cupf), trifluoroacetylacetonato (tfaa), and (methyl 2-(methylamino)-1-cyclopentene-1-dithiocarboxylato-κN,κS) (macsm)) were synthesized, characterized, and their rates of oxidative addition with methyl iodide were determined. Formation of an isosbestic point during the oxidative addition of methyl iodide with the complexes containing tfaa and cupf as bidentate ligands indicated formation of only one product, while an increase in absorbance maximum observed for macsm confirms that the same reaction between the complex and methyl iodide occurs. Kinetic results for all complexes, except [Ir(tfaa)(cod)], showed simple second-order kinetics with a zero intercept (within experimental error). Rates of oxidative addition for bidentate ligands in acetonitrile showed an increase of an order of magnitude with a change in the type of bidentate ligands. Computational chemistry using density functional theory calculations showed that the oxidative addition reaction proceeds through a “linear” transition state with the methyl iodide unit tilted towards the LL′-bidentate ligand.
Purification and characterization of a monohalomethane-producing enzyme S-adenosyl-L-methionine: Halide ion methyltransferase from a marine microalga, Pavlova pinguis
Ohsawa, Noboru,Tsujita, Mika,Morikawa, Satoru,Itoh, Nobuya
, p. 2397 - 2404 (2001)
A monohalomethane-producing enzyme, S-adenosyl-L-methionine-dependent halide ion methyltransferase (EC 2.1.1.-) was purified from the marine microalga Pavlova pinguis by two anion exchange, hydroxyapatite and gel filtration chromatographies. The methyltransferase was a monomeric molecule having a molecular weight of 29,000. The enzyme had an isoelectric point at 5.3, and was optimally active at pH 8.0. The Km, for iodide and SAM were 12 mM and 12 μM, respectively, which were measured using a partially purified enzyme. Various metal ions had no significant effect on methyl iodide production, suggesting that the enzyme does not require metal ions. The enzyme reaction strictly depended on SAM as a methyl donor, and the enzyme catalyzed methylation of the I , Br , and Cl- to corresponding monohalomethanes and of bisulfide to methyl mercaptan.
Rate Constants for Oxidation Reactions by Radical Cations from Methyl Iodide
Mohan, Hari,Asmus, Klaus-Dieter
, p. 118 - 122 (1988)
Radical cations from methyl iodide, CH3I.+, and are shown to be excellent oxidants with a one-electron redox potential presumably >/= +2 V.Absolute rate constants in the order of 1E9 M-1s-1 have been determined for their reactions with various organic sulfides, disulfides thiols, phenothiazines, and inorganic metal and halide ions.A similarly high reactivity has also been found for the hydroxyl radical adduct to methyl iodide, CH3I(OH)..The results are discussed in view of electronic and steric structure of these oxidizing radical species and the substrates to be oxidized.
The Decomposition of Acidic Karl Fischer Reagent in Methanol
Fischer, Wolfgang,Beckenkamp, Konrad
, p. 58 - 62 (1998)
The reaction between sulfur dioxide and iodine in methanol is started by traces of water in the solvent. Hydrogen iodide is formed and reacts with methanol to produce more water until all iodine is used up. An addition compound between iodine and hydrogen sulfite was found as an intermediate and characterized by Raman spectroscopy. Elementary sulfur is formed in a second reaction.
Thermal behaviour of a modified encapsulation agent: Heptakis-6-iodo-6-deoxy-beta-cyclodextrin
Fulia, Adriana,Vlase, Gabriela,oica, Codrua,Bercean, Vasile,Vlase, Titus,Ledei, Ionu
, p. 961 - 966 (2014)
Thermal behaviour of heptakis-6-iodo-6-deoxy-beta-cyclodextrin (HIDBCD) under inert and oxidative conditions was investigated by TG/DTG/DTA, FTIR, and using the hyphenate technique TG-FTIR. Due to the fact that thermal behaviour of HIDBCD was not studied before, we set our goal in the investigation of thermal degradation process in a dynamic air atmosphere vs. nitrogen atmosphere at a heating rate of 10 °C min-1, up to 500 °C, respectively, 600 °C. It was found that the degradation process in air occurs in a single step, with a total mass loss of 99.9 %. The results of TG/DTG/DTA-FTIR indicated that the thermal behaviour of this cyclodextrin can be divided into three stages and more information was provided about the reaction sequences and the relevant products of reaction.
Kinetics of the R + HBr → RH + Br (R = CH2I or CH3) reaction. An ab initio study of the enthalpy of formation of the CH2I, CHI2 and CI3 radicals
Seetula, Jorma A.
, p. 455 - 460 (2002)
The kinetics of the reaction of the CH2I and CH3 radicals, R, with HBr have been investigated separately in a heatable tubular reactor coupled to a photoionization mass spectrometer. The CH2I (or CH3) radical was produced homogeneously in the reactor by a pulsed 248 or 351 nm exciplex laser photolysis of CH2I2 (or CH3I). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately over a wide ranges of temperatures and the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1σ + Student's t values, units in cm3 molecule-1 s-1): k(CH2I + HBr) = (3.8 ± 0.7) × 10-13 exp[+ (1.4 ± 0.6) kJ mol-1/RT] and k(CH3 + HBr) = (2.3 ± 0.5) × 10-12 exp[+ (0.60 ± 0.17) kJ mol-1/RT]. The threshold energies of the reverse reactions, Br + R′H → R′ + HBr (R′ = CH2I, CHI2 or CI3), were calculated by ab initio methods at the MP2(fc)/6-311G(df)//MP2(fc)/6-311G(df) level of theory. These were combined with the experimentally determined activation energies of the forward reactions in a second-law method to determine the enthalpies of the reactions. The enthalpy of formation values at 298 K are (in kJ mol-1): 228.0 ± 2.8 (CH2I), 314.4 ± 3.3 (CHI2) and 424.9 ± 2.8 (CI3). The C-H bond strengths of analogous iodomethanes are (in kJ mol-1): 431.6 ± 2.8 (CH3I), 412.9 ± 3.3 (CH2I2) and 391.9 ± 3.1 (CHI3). The Arrhenius expression of the reverse reactions as determined by the thermodynamic transition state theory. The entropies of activation of the reactions were obtained by ab initio calculations.
Methyl sulfates as methoxy isotopic reference materials for δ13C and δ2H measurements
Greule, Markus,Keppler, Frank,Moossen, Heiko,Geilmann, Heike,Brand, Willi A.
, p. 343 - 350 (2019)
Rationale: Stable hydrogen and carbon isotope ratios of methoxy groups (OCH3) of plant organic matter have many potential applications in biogeochemical, atmospheric and food research. So far, most of the analyses of plant methoxy groups by isotope ratio mass spectrometry have employed liquid iodomethane (CH3I) as the reference material to normalise stable isotope measurements of these moieties to isotope–δ scales. However, comparisons of measurements of stable hydrogen and carbon isotopes of plant methoxy groups are still hindered by the lack of suitable reference materials. Methods: We have investigated two methyl sulfate salts (HUBG1 and HUBG2), which exclusively contain carbon and hydrogen from one methoxy group, for their suitability as methoxy reference materials. Firstly, the stable hydrogen and carbon isotope values of the bulk compounds were calibrated against international reference substances by high-temperature conversion- and elemental analyser isotope ratio mass spectrometry (HTC- and EA-IRMS). In a second step these values were compared with values obtained by measurements using gas chromatography/isotope ratio mass spectrometry (GC/IRMS) where prior to analysis the methoxy groups were converted into gaseous iodomethane. Results: The 2H- and 13C isotopic abundances of HUBG1 measured by HTC- and EA-IRMS and expressed as δ-values on the usual international scales are ?144.5 ± 1.2 mUr (n = 30) and ?50.31 ± 0.16 mUr (n = 14), respectively. For HUBG2 we obtained ?102.0 ± 1.3 mUr (n = 32) and +1.60 ± 0.12 mUr (n = 16). Furthermore, the values obtained by GC/IRMS were in good agreement with the HTC- and EA-IRMS values. Conclusions: We suggest that both methyl sulfates are suitable reference materials for normalisation of isotope measurements of carbon of plant methoxy groups to isotope–δ scales and for inter-laboratory calibration. For stable hydrogen isotope measurements, we suggest that in addition to HUBG1 and HUBG2 additional reference materials are required to cover the full range of plant methoxy groups reported so far.
Electronically Excited States of the CH3I2+ Ion
Griffiths, William J.,Harris, Frank M.,Parry, David E.
, p. 2801 - 2804 (1990)
A double-charge-transfer spectroscopy study has provided evidence for the existence of four low-lying electronic states of the CH3I2+ ion, the double-ionization energies to which are 27.0 +/- 0.3, 29.6 +/- 0.3, 31.3 +/- 0.5 and 36.5 +/- 0.5 eV.Three of these energies agree, within experimental error, with those determined previously in a dissociative double photoionization study of CH3I.The present investigation reveals for the first time the state at 29.6 eV.The value of the double-ionization energy to the ground triplet state, calculated in the present investigation using the single-determinant Hartree-Fock approximation to the many-electron wavefunction with corrections of second-order Moeller-Plesset perturbation theory for correlation effects, is 25.80 eV, somewhat lower than the measured value of 27.0 eV.
Diiodosilane. 1. A Novel Reagent for Deoxygenation of Alcohols and Ethers
Keinan, Ehud,Perez, Daniel
, p. 4846 - 4851 (1987)
Diiodosilane (DIS), which has never been used previously in organic synthesis, has been shown to exhibit properties and reactivities that are complementary to those of iodotrimethylsilane.This new reagent was used to cleave and deoxygenate ethers and alcohols with high selectivity for secondary oxygen functions.Synthesis of DIS is easily and rapidly carried out by reacting phenylsilane with iodine.
