Carbon Iodine Research Articles

Measuring the rate constant of the reaction between carbon monoxide and iodine oxide at 298–363 K by the resonance fluorescence method

The rate constant of the reaction between the IO radical and carbon monoxide has been measured by the iodine atom resonance fluorescence method in the temperature range from 298 to 363 K. The reaction mainly takes place on the wall of the reactor.

Design of Benign Initiator for Living Cationic Polymerization of Vinyl Ethers: Facile in Situ Generation of Vinyl Ether–Hydrogen Halide Adducts and Subsequent Controlled Polymerization without a Lewis Acid Catalyst

A Lewis acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis acid catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...

Structural dynamics effects on the ultrafast chemical bond cleavage of a photodissociation reaction

The correlation between chemical structure and dynamics has been explored in a series of molecules with increasing structural complexity in order to investigate its influence on bond cleavage reaction times in a photodissociation event. Femtosecond time-resolved velocity map imaging spectroscopy reveals specificity of the ultrafast carbon-iodine (C-I) bond breakage for a series of linear (unbranched) and branched alkyl iodides, due to the interplay between the pure reaction coordinate and the rest of the degrees of freedom associated with the molecular structure details. Full-dimension time-resolved dynamics calculations support the experimental evidence and provide insight into the structure-dynamics relationship to understand structural control on time-resolved reactivity.

ChemInform Abstract: Lithiation of Prochiral 2,2′‐Dichloro‐5,5′‐dibromo‐4,4′‐bipyridine as a Tool for the Synthesis of Chiral Polyhalogenated 4,4′‐Bipyridines.

Lithiation of the achiral tetrahalogenated 4,4′-bipyridine 1 with alkyllithiums was investigated. n-BuLi was found to induce either the chlorine-directed deprotolithiation reaction alone or with a concomitant halogen–lithium exchange furnishing after iodine trapping chiral 4,4′-bipyridines 2 and 6, respectively. The role of n-BuLi in the deprotolithiation process of 1 was elucidated on the basis of isolated secondary derivatives. After deprotolithiation, the lithiated species could be trapped by different electrophiles such as MeI, TMSCl, MeSSMe, R3SnCl (R = Me or n-Bu), and PPh2Cl. Moreover, 4,4′-bipyridine 2 was submitted to cross-coupling reactions (Suzuki and Sonogashira) which occurred selectively at the carbon–iodine bond. All compounds of this new family of atropisomeric 4,4′-bipyridines were separated by chiral HPLC (high-performance liquid chromatography), and the absolute configurations of obtained enantiomers were mainly assigned by XRD (X-ray diffraction) using anomalous dispersion.

Electro-catalytic scission of carbon–iodine bonds. Building of SAMs at gold surfaces through long chain primary radical adsorption

Primary alkyl iodides (RI) are reduced at smooth gold electrodes in polar organic solvents such as N,N-dimethylformamide (DMF) in the presence of tetraalkylammonium salts (TAAX). Beside a main two-electron step currently observed at potential>−2.0V vs. Ag/AgCl, a bell-shaped step appears with all organic iodides within a potential range between −0.6V and −1.2V. This peak does not depend on the organic substrate concentration, its current is proportional to the scan rate in voltammetry; it disappears at the second scan. These features arise from slow adsorption of the RI at gold, followed by an electro-catalytic reduction induced by the metal. It is expected that this (simple) process allows the formation of alkyl radicals readily adsorbed at the metal surface and thus produced layer strongly inhibits the main cathodic step at more negative potentials. With linear chains in C10, C12, C16 and C18, the coverage of gold leads to self-assembled monolayers (SAMs). The compactness of this coverage was found to be about 10−10molcm−2.

The origin of diffuse scattering in crystalline carbon tetraiodide

Total scattering neutron powder diffraction measurements were performed on the tetragonal phase (a=6.4202(5) Å, c=9.5762(12) Å) of CI4. The experiments were followed by reverse Monte Carlo (for powder diffraction) modelling. Detailed analyses of the resulting particle configurations revealed that the observed diffuse scattering originates from the libration of the molecules. By examining the partial radial distribution functions a distinct carbon–iodine peak at 4.5 Å is found, which appears as a consequence of corner-to-face mutual alignment of two molecules. The occurrence of edge-to-edge alignments is also significant within the first carbon–carbon coordination shell.

Poly(arylene ether)s with Pendent 3-Iodophenyl Sulfonyl Groups: Synthesis, Characterization, and Modification

A series of poly(arylene ether)s carrying truly pendent functional groups were prepared by the meta activated nucleophilic aromatic substitution (NAS) polycondensation reaction of a new aryl difluoride monomer, 3,5-difluoro-1-((3-iodophenyl)sulfonyl)benzene, followed by Suzuki–Miyaura and Heck cross-coupling reactions. The synthesis of 3,5-difluoro-1-((3-iodophenyl)sulfonyl)benzene was achieved via the one-step reaction of 3,5-difluorodiphenyl sulfone with N-iodosuccinimide. Model reactions and NMR data indicated that the carbon–iodine functionality was stable to NAS conditions, thus allowing the synthesis of the desired iodo functional poly(arylene ether sulfone), I-PAES. The iodo moiety was then subjected to palladium-catalyzed cross-coupling reactions with phenyl, naphthyl, and 4-acetylphenyl boronic acids as well as styrene in order to prepare the corresponding phenyl, naphthyl, 4-acetyl phenyl, and 2-phenylvinyl analogues. The polymers were characterized via NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. The polymers exhibited moderate thermal stability in air, with 5% weight loss temperatures ranging from 404 to 482 °C, while the glass transition temperatures ranged from 131 to 165 °C.

ChemInform Abstract: Functionalized Chromans and Isochromans via a Diastereoselective Pd(0)‐Catalyzed Carboiodination.

A diastereoselective approach to isochromans and chromans via Pd(0)-catalyzed carboiodination is reported. The transformations using this methodology display excellent yields and diastereoselectivities as well as broad functional group compatibility. The selectivity observed in these cyclizations, forming isochroman or chroman targets, is postulated to originate from the minimization of A1,2 strain and axial–axial interactions, respectively. This method has also been used to highlight the concept of reversible oxidative addition to carbon–iodine bonds in polyiodinated substrates.

Use of Silver Cathodes to Promote the Direct Reduction and Intramolecular Cyclization of ω-Halo-1-phenyl-1-alkynes in Dimethylformamide

Electrochemical reduction of 6-bromo- and 6-iodo-1-phenyl-1-hexyne and of 7-bromo- and 7-iodo-1-phenyl-1-heptyne at a silver cathode in dimethylformamide (DMF) containing 0.050 M tetramethylammonium perchlorate (TMAP) has been investigated with the aid of cyclic voltammetry and controlled-potential (bulk) electrolysis. Cyclic voltammograms for each bromo compound show a single irreversible cathodic peak for scission of the carbon–bromine bond, whereas two irreversible cathodic peaks are associated with reduction of the carbon–iodine bond of each iodo species. Radical intermediates arising from one-electron reduction of these ω-halo-1-phenyl-1-alkynes at silver undergo intramolecular cyclization to afford benzylidenecycloalkanes; other products include alkynes, enynes, and dimeric species. Electrolyses of 6-iodo-1-phenyl-1-hexyne and 7-iodo-1-phenyl-1-heptyne afford the desired benzylidenecycloalkane in higher yield than do electrolyses of the corresponding brominated compounds. Benzylidenecyclopentane is obtained in up to 85% yield when 6-iodo-1-phenyl-1-hexyne is reduced at a silver electrode held at a potential that corresponds to the first cathodic peak for this substrate; moreover, if the solvent–electrolyte is dried with activated alumina, one can achieve 99% conversion of 6-iodo-1-phenyl-1-hexyne to benzylidenecyclopentane. Studies involving the use of a deuterium atom donor (DMF-d7) or a deuterium ion donor (D2O) offer evidence that radicals and carbanions are both involved as intermediates in the formation of products.

Correlation between 13C chemical shifts and the halogen bonding environment in a series of solid para-diiodotetrafluorobenzene complexes

The co-crystallization of para-diiodotetrafluorobenzene (p-DITFB) with ammonium and phosphonium halide (Cl− and Br−) salts afforded four new compounds, [(n-Bu4PCl)(p-DITFB)] (2), [(n-Bu4NBr)(p-DITFB)] (3), [(n-Bu4PBr)(p-DITFB)] (4), and [(EtPh3PBr)2(p-DITFB)] (5), that exhibit moderately strong halogen bonding interactions. They have been characterized by single-crystal X-ray diffraction and 13C solid-state nuclear magnetic resonance (SSNMR) spectroscopy in magnetic fields of 9.4 and 21.1 T. The X-ray crystallography shows that in 2, 3, and 4, the halide is ditopic and forms long polymeric zigzag chains, whereas the bromide in 5 forms a dianionic species when involved in halogen bonding interactions. The NMR data, when combined with zeroth-order regular approximation density functional theory (ZORA–DFT) calculations, provide insight into the relationship between the strength of the halogen bond and the 13C isotropic chemical shift. When the carbon–iodine bond length increases, the 13C chemical shift also increases. Further insights into the relationship between halogen bonding and the 13C chemical shifts are obtained through additional systematic ZORA–DFT calculations as a function of the halogen bonding environment.

Quantitative structure—plasma protein binding relationships of acidic drugs

One of the most important factors, affecting significantly the overall pharmacokinetic and pharmacodynamic profile of a drug, is its binding to plasma protein (PPB). In the present study, we focus on a set of 132 diverse acidic drugs binding to plasma proteins to different extent and develop quantitative structure-plasma protein binding relationships (QSPPBR) to predict their unbound fraction in plasma (f(u)) using 178 molecular descriptors. QSPPBR models were derived after variable selection by genetic algorithm followed by stepwise regression and tested by cross- and external validation. The final model has r(2) value of 0.771, q(2) value of 0.737, and four outliers. It predicts 57% of the f(u) values with less than twofold error. According to the molecular descriptors selected as the most predictive for PPB, the lipophilicity of the drugs, the presence of aromatic rings, cyano groups, and H-bond donor-acceptor pairs increase the PPB, whereas the presence of tertiary carbon atoms, four-member rings, and iodine atoms decrease PPB. These descriptors were summarized into a short seven-item checklist of criteria responsible for PPB. The checklist could be used as a guide for evaluation of PPB of acidic drug candidates, similarly to the Lipinski's rule of five used for evaluation of oral permeability of drugs.

Base-Promoted Aryl Carbon–Iodine and Carbon–Bromine Bond Cleavage with Rhodium Porphyrin Complexes: Scope and Mechanism

Base-promoted aryl carbon–iodine and carbon–bromine bond (Ar–X, X = I, Br) cleavage by rhodium porphyrin complexes was achieved to give the rhodium(III) porphyrin aryls Rh(ttp)Ar (ttp = tetra-p-tolylporphyrinato dianion). Mechanistic studies showed that RhII2(ttp)2 is the intermediate for Ar–X (X = I, Br) cleavage. The Ar–X cleavage process goes through a rhodium(II) porphyrin radical mediated ipso-substitution mechanism.

Preparation of highly carbonized material from nanoparticle impregnated biomass

In this study, we impregnated nanometal samples having various concentrations 0, 1000, 3000, and 5000ppm in biomass in order to make carbonized biomass. We analyzed the properties of the impregnated samples through thermogravimetry/differential thermal analysis (TG–DTA), iodine adsorptivity, fixed carbon ratio, pore distribution, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The best results were observed for a nanometal concentration of 5000ppm. After the first heat treatment, carbonization, and activation processes, the fixed carbon ratio and iodine adsorptivity were increased by 11.07% and 42mg/g, 11.07% and 198mg/g, and 46.7% and 1185mg/g, respectively. Through repeated experiments, we established the most effective process for impregnating a nanometal in biomass.

Evidence for formation of ion pair stabilized diiodomethane radical anion in 1-butyl-3-methylimidazolium tetrafluoroborate room temperature ionic liquid

Voltammetric investigations on diiodomethane (CH2I2) in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) are reported. Presented investigations show that, electroreduction of CH2I2 follows a typical irreversible redox behavior, where in initial electron transfer is the rate determining step. Electroreductive cleavage of carboniodine (CI) bond in CH2I2 is discussed in light of Marcus–Hush quadratic activation-driving force theory. The experimental findings establish that the dissociative electron transfer of CI bond in [BMIM][BF4] follows a stepwise pathway, which is a direct experimental evidence for formation of ion pair stabilized radical anion in RTIL. The reported results establish the role of RTILs in stabilization of electrogenerated intermediate and their subsequent chemistry in an electro-synthetic pathway.

Prepared Activated Carbon from Rice Husk Cracking by Medium Optimization Using a Statistical Experimental Design

Response surface methodology was used to optimize the activated carbon iodine absorption value screened by Placket-Burman design. Six effective factors such as NaOH concentrations, boiling time, liquid ratio, calcined ways, calcined time and calcined temperature were tested by using Placket-Burman design criterion and three effective factors NaOH concentrations, liquid ratio and calcined time showed significant effect(P<0.05) on iodine absorption value. By applying Box-Behnken design, the optimized condition obtained NaOH concentrations of 2.5mol/l, liquid ratio of 1/1.125 and calcined time of 37.5min. Three runs of additional confirmation experiments were conducted. The average relative error was 0.58%.

Base-Promoted Selective Aryl C–Br and C–I Bond Cleavage by Iridium(III) Porphyrin: Reduction of IrIII–OH to IrII for Metalloradical Ipso Substitution of Aryl–Halogen Bonds

Base-promoted selective aryl carbon–bromine and carbon–iodine bond (Ar–X, X = Br, I) cleavage by iridium(III) porphyrin carbonyl chloride (IrIII(ttp)(CO)Cl) was achieved in the presence of base (K2CO3, NaOH) to give iridium(III) porphyrin aryls (IrIII(ttp)Ar). Mechanistic studies revealed that the base undergoes ligand substitution with Ir(ttp)(CO)Cl to yield an iridium(III) hydroxo species (IrIII(ttp)OH). The hydroxo ligand most likely reduces the Ir(III) center to give iridium(II) porphyrin dimer ([IrII(ttp)]2) and H2O2. In a competitive pathway, [IrII(ttp)]2 disproportionates in the presence of base and residual water to give an iridium(III) hydride (IrIII(ttp)H) and Ir(ttp)OH. In a productive process, [Ir(ttp)]2 undergoes IrII(ttp) metalloradical-mediated ipso substitution of Ar–X via an addition–elimination pathway to form Ir(ttp)Ar and Ir(ttp)X. Ir(ttp)X is recycled by reacting with base to regenerate [Ir(ttp)]2 for subsequent Ar–X cleavage.

Technology Optimization Study on Preparation of Activated Carbon from Rice Husk Cracking

Response surface methodology (RSM) was adopted to study the key parameters such as activation temperature, activation time, and active agent amount in order to increase activated carbon iodine adsorption value from rice husk. A second order quadratic equation was established and the applicability of model and interaction involved factors on predicting the iodine adsorption value was verified. The results indicated that the effect on the iodine adsorption value was as follows: activation temperature, activation ratio, activation time. The optimal levels for achieving the highest iodine adsorption value were obtained, including activation temperature of 550°C, activation time of 48min and activation ratio of 1.25. The iodine adsorption value reached 1464.793mg/g under optimized conditions. Iodine adsorption value was conducted under the optimum condition and the results showed the average relative error 0.58%, it proved that the models fitted well, the experimental data and the model were feasible.

Synthesis and characterization of aromatic polyamides derived from various derivatives of 4,4’-oxydianiline

Three aromatic diamines, 2,2′-diiodo-4,4′-oxydianiline (DI-ODA 2), 2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′-oxydianiline (BTFP-ODA 3) and 2,8-diaminodibenzofuran (DADBF 5) were synthesized by using 4,4-oxydianiline (4,4′-ODA) as the starting material. New aromatic polyamides 6, 7 and 8 were prepared from these three diamines and six commercially available aromatic diacids by direct polycondensation, respectively. Polyamides 6 and 7 contained bulky iodide and p-trifluoromethylphenyl substitutents that would hinder the chain packing and increase the free volume. They exhibited good optical transparency in visible light region and showed excellent solubility in organic solvents such as DMSO, DMAc, DMF and NMP. Polyamides 8 containing planar dibenzofuran moieties had the highest glass transition temperatures and decomposition temperatures among these polyamides. Polyamides 6 had the lowest decomposition temperatures due to the presence of weak carbon–iodine bond. All of these polyamides showed amorphous nature evidenced by wide angle X-ray diffraction. No endothermic peaks were observed from DSC thermograms up to their decomposition temperatures. High optical transparency and excellent solubility combined with good thermal stability make these polyamides attractive for potential soft electronics applications.

Facile Synthesis of Coumarinyl Isothiocyanate from Amino Coumarin

One-pot conversion of amino coumarin to corresponding coumarinyl isothiocyanate using carbon disulfide, iodine, and pyridine is described. In this reaction, pyridine acts as a solvent as well as a catalyst to give coumarinyl isothiocyanate. Excellent yield, short reaction time, and mild reaction conditions make this method a useful synthetic procedure for one-pot preparation of coumarinyl isothiocyanate.

Conceptual design of a bioregenerative life support system containing crops and silkworms

This article summarizes a conceptual design of a bioregenerative life support system for permanent lunar base or planetary exploration. The system consists of seven compartments – higher plants cultivation, animal rearing, human habitation, water recovery, waste treatment, atmosphere management, and storages. Fifteen kinds of crops, such as wheat, rice, soybean, lettuce, and mulberry, were selected as main life support contributors to provide the crew with air, water, and vegetable food. Silkworms fed by crop leaves were designated to produce partial animal nutrition for the crew. Various physical-chemical and biological methods were combined to reclaim wastewater and solid waste. Condensate collected from atmosphere was recycled into potable water through granular activated carbon adsorption, iodine sterilization, and trace element supplementation. All grey water was also purified though multifiltration and ultraviolet sterilization. Plant residue, human excrement, silkworm feces, etc. were decomposed into inorganic substances which were finally absorbed by higher plants. Some meat, ingredients, as well as nitrogen fertilizer were prestored and resupplied periodically. Meanwhile, the same amount and chemical composition of organic waste was dumped to maintain the steady state of the system. A nutritional balanced diet was developed by means of the linear programming method. It could provide 2721 kcal of energy, 375.5 g of carbohydrate, 99.47 g of protein, and 91.19 g of fat per capita per day. Silkworm powder covered 12.54% of total animal protein intakes. The balance of material flows between compartments was described by the system of stoichiometric equations. Basic life support requirements for crews including oxygen, food, potable and hygiene water summed up to 29.68 kg per capita per day. The coefficient of system material closure reached 99.40%.