Iodine Monobromide Research Articles

ChemInform Abstract: Polycyclic Quinolones. Part 2. Synthesis of Novel 4‐Oxo‐1,4‐dihydrobenzo[h][1,3]thiazeto[3,2‐a]quinoline Carboxylic Acids via Oxidative Cyclization of the Corresponding 2‐Mercaptoquinoline Precursors.

AbstractSticking point in the formation of the 1,3‐thiazeto[3,2‐a]quinoline skeleton is a cyclization step using the system vicinal dihaloalkane / potassium iodide as a controlled source of iodine monobromide which halogenates the carbon α to the thiol.

The interaction of halogen molecules with SWNTs and graphene

The interaction of halogen molecules of varying electron affinity, such as iodine monochloride (ICl), bromine (Br2), iodine monobromide (IBr) and iodine (I2) with single-walled carbon nanotubes (SWNTs) and graphene has been investigated in detail. Halogen doping of the two nanocarbons has been examined using Raman spectroscopy in conjunction with electronic absorption spectroscopy and extensive theoretical calculations. The halogen molecules, being electron withdrawing in nature, induce distinct changes in the electronic states of both the SWNTs and graphene, which manifests with a change in the spectroscopic signatures. Stiffening of the Raman G-bands of the nanocarbons upon treatment with the different halogen molecules and the emergence of new bands in the electronic absorption spectra, both point to the fact that the halogen molecules are involved in molecular charge-transfer with the nanocarbons. The experimental findings have been explained through density functional theory (DFT) calculations, which suggest that the extent of charge-transfer depends on the electron affinities of the different halogens, which determines the overall spectroscopic properties. The magnitude of the molecular charge-transfer between the halogens and the nanocarbons generally varies in the order ICl > Br2 > IBr > I2, which is consistent with the expected order of electron affinities.

Bi- and trilayer graphene solutions

Bilayer and trilayer graphene with controlled stacking is emerging as one of the most promising candidates for post-silicon nanoelectronics. However, it is not yet possible to produce large quantities of bilayer or trilayer graphene with controlled stacking, as is required for many applications. Here, we demonstrate a solution-phase technique for the production of large-area, bilayer or trilayer graphene from graphite, with controlled stacking. The ionic compounds iodine chloride (ICl) or iodine bromide (IBr) intercalate the graphite starting material at every second or third layer, creating second- or third-stage controlled graphite intercolation compounds, respectively. The resulting solution dispersions are specifically enriched with bilayer or trilayer graphene, respectively. Because the process requires only mild sonication, it produces graphene flakes with areas as large as 50 µm(2). Moreover, the electronic properties of the flakes are superior to those achieved with other solution-based methods; for example, unannealed samples have resistivities as low as ∼1 kΩ and hole mobilities as high as ∼400 cm(2) V(-1) s(-1). The solution-based process is expected to allow high-throughput production, functionalization, and the transfer of samples to arbitrary substrates.

Freeze-Induced Reactions: Formation of Iodine−Bromine Interhalogen Species from Aqueous Halide Ion Solutions

Interhalide ion formation resulting from the freezing of dilute solutions containing components found in natural sea salt are investigated as a potential mechanism for the release of interhalogens to the polar atmosphere. Acidified solutions containing iodide, bromide, and nitrite ions have been frozen and then thawed, with changes in speciation analyzed using UV-visible spectrophotometry. The freezing process is shown to induce the formation of the important interhalide ion, IBr(2)(-). This species has previously been predicted to be a precursor of iodine monobromide, IBr, and represents a potentially important source of halogen atoms in the polar marine boundary layer. The reaction mechanisms that lead to the formation of IBr(2)(-) under freezing conditions are explored using both experimental and computational methodologies. The chemistry involved was subsequently modified in order to mimic naturally occurring conditions more closely and also incorporated the use of hydrogen peroxide as an oxidant. In contrast to previous studies, the freeze-induced production of IBr(2)(-) was thereby observed to occur up to pH <5.1, where the acidity levels are comparable to those found in the polar snowpack.

Modern methods to determine vitamin E in foods and feeds

Highly specific and sensitive, the proposed fluorometric method for determining α-tocopherol is robust and fairly fast. Ithas been tested in parallel with a conventional thin layer chromatographic method on foods and feeds. The only necessarycleanup is the usual saponification. The unsaponificable fraction can be extracted with ethyl ether or, preferably, withExtrelut columns. Reagents and their solvents are added to the isooctane solution before each successive reaction and arethen eliminated by partition with water. The α-tocopherol (α-T) derivative always remains in isooctane. The first step isnitrosation and elimination of tocopherols and tocotrienols other than α-isomers. α-T is then oxidized to α-tocored (α-TR)with a mixture of sulfuric acid, ferric chloride, and iodine bromide. Α-TR is then condensed to a new reagent: 4,5-dimethylo-phenylenediamine. The phenazine formed is strongly fluorescent. Iodine and bromine add to the double bonds of α-tocotrienol present and quench the fluorescence of its phenazine.

On the unimolecular elimination of gas-phase iodine monobromide following excitation in the visible wavelength region

Dissociation dynamics of iodine monobromide has been theoretically investigated at numerous excitation wavelengths in the visible wavelength region (450–540 nm) by an accurate time-dependent dynamical simulation technique. The interatomic potential energy curves are derived from ab initio methods which are then employed in a Landau–Zener treatment to calculate the spin-orbit branching ratios in the two halogen products. The extinction coefficients, in arbitrary units, for the discrete electron transition are obtained through a numerical algorithm. Based on these elastic scattering calculations, the results of Br*: Br branching ratios are determined at several simulation wavelengths. Also the electronic properties are evaluated to elucidate the mechanism of chemical dynamics of the system. It is found that the branching dynamics can be clarified via the Landau–Zener model, which treats an avoided crossing between two states of a given nature and evaluates a nonadiabatic effect relevant to the dissociation of IBr molecule.

A Mild, Highly Efficient, and Chemoselective Deprotection of Trityl Ethers of Carbohydrates and Nucleosides Using Iodine Monobromide¹

Iodine monobromide in dichloromethane-methanol or acetonitrile constitutes an effective reagent for the deprotection of O-trityl and O-dimethoxytrityl ethers of carbohydrates and nucleosides. Acid-labile functionalities (acetals, O-p-methoxybenzyl ethers, etc.) as well as base-labile groups (esters and amides) are stable under these conditions; and the method has been found to be superior to the hitherto known literature methods.

A denuder–impinger system with in situ derivatization followed by gas chromatography–mass spectrometry for the determination of gaseous iodine-containing halogen species

Reactive iodine species have been suggested to play an important role in the atmosphere (e.g. tropospheric ozone depletion, coastal new particle formation). However, there still exist major uncertainties about their atmospheric chemistry, mostly due to the lack of analytical approaches for the accurate speciation of certain key compounds. In this study, 1,3,5-trimethoxybenzene (1,3,5-TMB)-coated denuder proved to be suitable for the differentiation between gaseous interhalogens (iodine monochloride (ICl), iodine monobromide (IBr)) and molecular iodine (I 2) based on a selective collection/derivatization method. The results of the denuder sampling were compared with the results of impinger sampling in water, methanol and carbon tetrachloride solutions of 1,3,5-TMB. ICl and IBr are converted into 1-iodo-2,4,6-trimethoxybenzene (1-iodo-2,4,6-TMB) and 1-bromo-2,4,6-trimethoxybenzene (1-bromo-2,4,6-TMB), respectively, in the denuder systems. The respective collection efficiency is 99.2% for ICl and 92.6% for IBr, at 500 mL min −1 gas flow rate. The collection efficiency for I 2 is lower than 1% in the same denuder system, but significantly increases to about 90% in the aqueous 1,3,5-TMB loaded impinger. The denuder–impinger coupled system was then used to differentiate and to collect the ICl, IBr and I 2 gas mixtures, followed by gas chromatography–ion trap mass spectrometry (GC–MS) determination. The precision of the method is in general better than 9.1%. The parameters affecting denuder operation including sampling flow rate, sampling duration, and relative humidity have been evaluated. The presented method provides an attractive protocol for iodine species analysis for atmospheric chemistry research.

Time- and frequency-resolved coherent anti-Stokes Raman scattering spectroscopy with sub-25fs laser pulses

In general, many different diagrams can contribute to the signal measured in broadband four-wave mixing experiments. Care must therefore be taken when designing an experiment to be sensitive to only the desired diagram by taking advantage of phase matching, pulse timing, sequence, and the wavelengths employed. We use sub-25 fs pulses to create and monitor vibrational wavepackets in gaseous iodine, bromine, and iodine bromide through time- and frequency-resolved femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy. We experimentally illustrate this using iodine, where the broad bandwidths of our pulses, and Boltzmann population in the lower three vibrational levels conspire to make a single diagram dominant in one spectral region of the signal spectrum. In another spectral region, however, the signal is the sum of two almost equally contributing diagrams, making it difficult to directly extract information about the molecular dynamics. We derive simple analytical expressions for the time- and frequency-resolved CARS signal to study the interplay of different diagrams. Expressions are given for all five diagrams which can contribute to the CARS signal in our case.

Two Contrasting Asymmetric Approaches to Muscarine Based on 5‐endo‐trig Cyclisations

Abstract5‐endo‐trig cyclisation of the (Z)‐hydroxyalkenoate 17 using iodine as the electrophile gave a good yield of the β‐hydroxytetrahydrofuran 18, probably via the corresponding iodohydrin. A variety of one‐carbon degradation methods were then used to generate precursors to (−)‐muscarine (25d). An alternative strategy featured control of a 5‐endo‐trig iodocyclisation by an allylic hydroxyl group, which can be used for the highly stereocontrolled synthesis of hydroxy‐iodotetrahydrofurans 28. Application of this strategy to the (Z)‐alkenediol derivative 38 led to an excellent yield of the tetrahydrofuran 39 when iodine monobromide was used as the electrophile. Two simple and efficient transformations then gave the (+)‐muscarine precursor 40b. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)

Influence of iodine-bromide baths on some risk factors of ischemic heart disease

Influence of iodine-bromide baths on some risk factors of ischemic heart disease

1,3-Migration of Trimethylsilyl Group from Carbon to Oxygen in Highly Sterically Hindered Silanol of the Type (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH and Reaction of the Related Iodide with Iodine Monochloride and Iodine Monobromide

The silanol (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH has been shown to isomerize to (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) when it was kept at room temperature for 10 h in 0.2 M NaOMe/MeOH. Corresponding isomerizations of the above silanol (to give (Me 3 Si) 2 CHSi(C 6 H 4 Me- p ) (Me)(OSiMe 3 )) are complete after 26 h under reflux in pyridine. The reaction involve 1,3-migration from carbon to oxygen within a silanolate ion to give a carbanion, which rapidly acquires a proton from the solvent. Treatment of (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeOH with MeLi in Et 2 O/THF give, by the same rearrangement, the organolithium reagent (Me 3 Si) 2 CLiSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) which on treatment with Me 2 SiHCl gives (Me 3 Si) 2 C(SiMe 2 H)Si(C 6 H 4 Me- p )(Me)(OSiMe 3 ) and (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). When the experiment was repeated, but with Me 3 SiCl in place of Me 2 SiHCl, it gives exclusively (Me 3 Si) 2 CHSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). Treatment of the organolithium reagent (Me 3 Si) 2 CLiSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ) with Mel gives exclusively (Me 3 Si) 2 CMeSi(C 6 H 4 Me- p )(Me)(OSiMe 3 ). The related iodide (Me 3 Si) 3 CSi(C 6 H 4 Me- p )Mel reacts with ICI and IBr to give rearranged (Me 3 Si) 2 C(SiMe 2 X)Si(C 6 H 4 Me- p )Me 2 and unrearranged products (Me 3 Si) 3 CSi(C 6 H 4 Me- p )MeX, (X = Cl, Br) respectively. The rearranged bromide (Me 3 Si) 2 C(SiMe 2 Br)Si(C 6 H 4 Me- p )Me 2 reacts with a range of silver [I] salts AgY (Y = OOCCH 3 , SO 4 2 m ) and Mercury [II] salt HgY 2 (Y = OOCCH 3 , SO 4 2 m ) in glacial CH 3 COOH to give the corresponding species (Me 3 Si) 2 C(SiMe 2 OOCCH 3 )Si(C 6 H 4 Me- p )Me 2 . The reaction of the bromide with AgBF 4 in MeOH or i -PrOH give the corresponding rearranged products (Me 3 Si) 2 C(SiMe 2 Y)Si(C 6 H 4 Me- p )Me 2 (Y = --OMe, --OPr i ).

New powerful reagents based on dihalogen/N,N′-dimethylperhydrodiazepine-2,3-dithione adducts for gold dissolution: the IBr case

The synthesis, X-ray structure [monoclinic, P21/n, a = 12.1690(1), b = 7.8360(1), c = 14.4250(1) A, β = 113.808(2)°], spectroscopic and electrochemical characterization of a new powerful reagent based on the iodine monobromide adduct of the N,N′-dimethylperhydrodiazepine-2,3-dithione (Me2dazdt) ligand, able to oxidize gold metal in a one-step reaction under mild conditions, is reported. The gold metal dissolution has been performed on gold powder, wires and Au/Ti thin layers. The oxidation product has been isolated and structurally characterised as [Au(Me2dazdt)Br2]IBr2 [monoclinic, C2/c, a = 26.523(8), b = 10.191(6), c = 14.549(7) A, β = 111.57(2)°]. The metal is essentially within a square planar geometry, Me2dazdt acts as an S,S chelating ligand and two bromide ligands complete the geometry around the metal. The IBr2− counteranion is essentially linear and shows I–Br bond lengths slightly asymmetric [Br(4)–I(1) 2.742(3), Br(3)–I(1) 2.682(2) A]. A comparison with the gold removal from Si/SiO2/Au/Ti thin layers of comparable thickness to that found in microelectronic devices, by using THF solutions of IBr and I2 adducts of the Me2dazdt donor, as well as the currently used I2/I− aqueous solutions, shows that these dihalogens-adducts produce a quantitative gold removal in shorter times and leaving the underlying layer perfectly clean, and are thus highly desirable as new etching agents in the gold-based technology of semiconductor devices.

Synthesis of Cyclic Enol Ethers from Alkenyl‐β‐dicarbonyl Compounds.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Products of the determination of the iodine value with iodine monobromide.

The iodine value (iodine number) is an important analytical characteristic of fats and oils. Leading pharmacopeias determine it using iodine monobromide (Hanus method). We used methyl oleate as a simple analog of unsaturated triacylglycerols to identify the products. After performing the reaction in deuterated solvents under pharmacopeial conditions, NMR spectroscopy revealed the presence of the 9, 10-diiodo, 9, 10-dibromo, and 9, 10-bromoiodo adducts, leaving no educt olefin. The prescribed subsequent addition of potassium iodide led to the formation of methyl 9, 10-diiodo and bromoiodo stearate in equal amounts.

Dissociative multiple photoionization of Br 2, IBr, and I 2 in the VUV and X-ray regions: a comparative study of the inner-shell processes involving Br(3d,3p,3s) and I(4d,4p,4s,3d,3p)

Dissociative multiple photoionization of the bromine, the iodine monobromide, and the iodine molecules in the Br(3d,3p,3s) and I(4d,4p,4s,3d,3p) inner-shell regions has been studied by using time-of-flight (TOF) mass spectrometry coupled to synchrotron radiation in the ranges of 90∼978 eV for Br 2, 60∼133 eV for IBr, and 86∼998 eV for I 2. Total photoion and photoion–photoion coincidence (PIPICO) yields have been recorded as functions of the photon energy. Here, giant shape resonances have been observed beyond the thresholds of the inner-shells owing to the Br(3d 10)→Br(3d 9 ϵf), I(4d 10)→I(4d 9 ϵf), and I(3d 10)→I(3d 9 ϵf) transitions. The dissociation processes of the multiply charged parent ions have also been evaluated from variations of photoelectron–photoion coincidence (PEPICO) and PIPICO spectra with the photon energy. From each Br(3p 3/2) (189.9 eV) and I(4p 3/2) threshold (129.9 eV), quintuple ionization of the molecules begins to play important roles in the photoionization, subsequently yielding ion pairs of X 3+–X 2+ (X=Br, I). From the I(3d 5/2) threshold (627.3 eV), loss of six electrons from iodine molecule additionally begins to play a minor role in the multiple photoionization, giving rise to the formation of ion pairs of either I 3+–I 3+ or I 4+–I 2+. A direct comparison of the strengths and the ranges of the I(4d) and Br(3d) giant resonances was successfully made from dissociative photoionization of IBr. Over the entire energy range examined, 60< E<133 eV, biased charge spread relevant to the specific core-hole states of IBr is observed, presumably reflecting the fact that charge localizes mostly in the excited atoms, which can be accounted for mainly by a two step decay via a fast dissociation followed by autoionization upon the VUV absorption.

Determination of iodine values according to Hanuš using 1,3-dibromo-5,5-dimethylhydantoin (DBH): Analytical methods of pharmacopeias with DBH: part 7

USP/NF 2000 [The United States Pharmacopeia, Rockville USA, 24th ed., 2000, p. 1868, The National Formulary, 19th ed. 2000] and PH. EUR. 1997 [European Pharmacopoeia, third ed., Council of Europe, Strasbourg, 1997, pp. 63–64] determine the iodine values according to Hanuš with iodine monobromide in glacial acetic acid. This reagent can be replaced by a solution of 1,3-dibromo-5,5-dimethylhydantoin (DBH) and potassium iodide or iodine in the same solvent. Both reagents yield equivalent results by means of method comparison according to Passing and Bablok [J. Clin. Chem. Clin. Biochem. 21 (1983) 709; 22, (1984) 431] in relation to the official method of PH. EUR.

Preparation and crystal structure of tetraphenylphosphonium triiodotetrabromide [PPh4][I3Br4

Tetraphenylphosphonium triiodotetrabromide [PPh4][I3Br4] is obtained by the reaction of tetraphenylphosphonium bromide with iodine monobromide. It is the first example of an iodine rich, seven-membered polybromide. [PPh4][I3Br4] crystallizes triclinic in the space group P1 with a = 10.947(1) A, b = 11.945(1) A, c = 12.896(1) A, alpha = 66.80(1) degrees, beta = 77.21(1) degrees, gamma = 85.73(1) degrees, and two formula units per unit cell. The final R indices [I > 4 sigma(I)] are R1 = 0.0362 and wR2 = 0.0944.

The Distribution Constant of Iodine between Aqueous and Organic Phases

The distribution equilibrium constant of iodine between water and the water-insoluble organic solvent octamethylcyclotetrasiloxane was determined by a titrimetric method. Octamethylcyclotetrasiloxane is an alternative to the more commonly used carbon tetrachloride, which is suspected of causing cancer. The stability equilibrium constants for the iodine-chloride (I2Cl-) and iodine bromide (I2Br-) complex trihalide ions was also estimated from a linear least-squares graphical plot.

Thermoelectric Power of Stage-2 IRr-GIC

c-axis thermoelectric power (TEP) S c of stage-2 graphite intercalation compound with iodine monobromide (IBr-GIC) was measured below the room temperature, and the calculation was carried out by our theory. The major part of S c comes from the diffusion TEP S c-d. However, a slight deviation exists between S c-d and the experimental result S c and it can be removed in consideration of phonon drag TEP S c-p. This situation was different from the case of graphite intercalation compound with iodine monochrolide (ICI-GICs). Above the room temperature, we attempted to measure the TEP of stage-2 IBr-GIC. It shows the phase transition similar to the case in ICI-GICs.