CS2 Solution Research Articles

Recovery of acrylonitrile from charcoal tubes at low levels.

Data are presented for the recovery of acrylonitrile from charcoal tubes at levels lower than those tested in NIOSH Method S156. A 2% by volume acetone in CS2 solution is used as desorbing solvent. An injection volume of 2 muL and a 3-m long by 3.2-mm o.d. (10-ft x 1/8-in) stainless steel column filled with 20% SP-1000 on 80/100 Supelcoport gives adequate resolution of the acrylonitrile. Results indicate that recoveries are adequate for sample sizes which correspond to a 15-liter sample at 0.5 and 0.25 ppm, and that acrylonitrile collected on carbon in the absence of inhibitor is stable for at least a week.

Collection of Gas Chromatographic Fractions on Activated Charcoal and Identification by Infrared Spectroscopy

A novel method for collecting gas chromatographic fractions in commercially available tubes of activated charcoal has been developed and tested on a number of organic mixtures. The trapped fractions were desorbed with CS2 and infrared spectra of the CS2 solutions measured to provide positive identification of the eluents. The collection efficiency was found to be >68% in all but one case, and the resolution of the separation and collection method was adequate for making positive identifications. The advantages of using computerized subtraction of infrared spectra in identifying the eluents is also demonstrated.

Preparation, ligand-exchange reactions, and alkylation reactions of some carbon disulphide derivatives of iron

A number of [Fe(CO)2L2(η2-CS2)] complexes have been prepared from [Fe2(CO)9] and L in CS2 solution [L = PR3, P(OR)3, or CNR]. When L = P(OMe)3 a second unstable product is isolated which may be polynuclear. When L = CNMe or CNBut further reaction occurs to give [Fe(CO)L3(CS2)] and then a carbonyl-free complex. Ligand-exchange reactions of the complexes where L = PPh3 or P(OPh)3 with the phosphorus(III) ligands L′ gives [Fe(CO)2L(L′)(CS2)] rapidly and then [Fe(CO)2L′2(CS2)] much more slowly. The extent of this reaction depends on ligand size and is more complete for the less bulky L′. However, ligand basicity is also very important so that L′= AsBun3 displaces only one L = P(OPh)3 whilst with L′= SbEt3 even this reaction is incomplete. On the other hand the very bulky but basic L′= PPri3 will displace completely the less bulky but less basic L = P(OPh)3. Where L′= CNMe the reaction takes a different course with the formation of [Fe(CO)2L(CNMe)(CS2)] and then [Fe(CO)L(CNMe)2(CS2)]. Reagents such as L′= CO, SO2, [N2Ph]+, and X2(halogen) will displace CS2 to give [Fe(CO)2L2(L′)]. The η2-CS2 complexes are alkylated readily at the unco-ordinated sulphur atom, Su, forming [Fe(CO)2L2(CS2R)]+ salts which are relatively inert to exchange of L. Carbon disulphide is a powerful electron-withdrawing ligand. It is suggested that this is because it may accept electrons into (a) its C–SCπ* orbital as in olefin–metal bonding, (b) the vacant 3d orbitals on the co-ordinated sulphur atom Sc as in thioether–metal bonding, and (c) the C–Suπ* orbitals as in M–CS bonding with this last being particularly important. Also, it is suggested that, as a consequence of the importance of the metal-to-CS2 backbonding, η2-CS2 complexes are only stable if the metal centre is relatively electron-rich. Thus phosphorus ligands which are very basic but bulky, e.g. PPri3, will replace those which are less basic even if they are less bulky, e.g. P(OPh)3.

Notizen: Convenient Preparation and Vibrational Spectra of Cyclodecasulfur, S10, and of the Adduct S6 · S10 [1

Abstract Thermal decomposition of S6O2 and S7O, respectively, in CH2Cl2 or CS2 solution at temperatures between 20 and 5 °C yields SO2, polymeric sulfur and S10 which was obtained as pure single crystals in yields of 7-11% with regard to the starting materials S6 and S7, respectively. Infrared and Raman spectra of S10 as well as of the new molecular addition compound S6 · S10 are reported.

Proton magnetic resonance spectra of 3-fluorotoluene and 2-chloro-5-fluorotoluene. The sign and coupling mechanism of

A full analysis of the proton magnetic resonance spectra of 3-fluorotoluene and of 2-chloro-5-fluorotoluene, as 10 mol% solutions in CS2, demonstrates that the long-range spin–spin coupling constant over five bonds between methyl protons and fluorine-19 is negative. The coupling mechanism consists of a large positive σ electron component and a negative π electron component. The negative sign of the π electron contribution arises from a spin density in the 2pz orbital at carbon-3, which is opposite in sign to that of the spin densities at C-2 and C-4. Combined with positive hyperfine interaction constants, QCCH and QCF, the consequence is a negative π electron component.

Growth of Trigonal Selenium from CS2 Solution

Growth of Trigonal Selenium from CS2 Solution

Quasielastic scattering of neutrons from freely jointed polymer chains in dilute solutions

AbstractStarting with Kirkwood's Fokker–Planck equation for the polymer configuration‐space distribution function and using the Zwanzig–Mori projection operator technique we have calculated the scattering law S(q,w) for a freely jointed model polymer chain in a dilute solution. When memory effects are neglected, the theory predicts a Lorentzian for S(q,w) with a halfwidth Ω(q), which we have determined as a function of the momentum transfer q for all values of q. The results are compared with recent neutron scattering experiments on deuterated polytetrahydrofuran and polystyrene in dilute solution in CS2. It is found that the observed q dependence of Ω(q) is represented satisfactorily by the present theory with a bond length b of about 6.3 Å for polystyrene and 3.8 Å for polytetrahydrofuran, and a friction coefficient ζ = 4πη0b where η0 is the viscosity of the solvent.

Raman spectroscopic studies of chloroprene polymers

AbstractThe Raman spectra of predominantly trans ‐ 1,4‐polychloroprenes are presented. Spectra were recorded of polymers prepared by free radical emulsion techniques in the temperature range −20 to +40°C in both the solid state and in CS2 solution. Spectral changes characteristic of the crystalline and amorphous regions of the polymers have been identified. Measurements of the relative broadness of the 1007 cm−1 Raman line, which is associated with the C‐C stretching frequency in the main chain, have been made and correlated with the amorphous content of the polymer. Extrapolations of these results indicates that polymers prepared in the range 50–60°C should be completely amorphous elastomeric materials.

Vibrational and high pressure conformational studies of 1,1,2-trichloroethane

The infrared spectra of 1,1,2-trichloroethane were recorded from 4000 to 50 cm−1 in the vapour and liquid states. Additional spectra above 200 cm−1 of the low temperature crystal and of two crystalline solids, prepared by compressing the sample in a diamond anvil cell, were obtained. Also, infrared spectra of the liquid and of the compound dissolved in CS2 were recorded at increased pressures. Raman spectral data of the liquid (including polarization measurements) and of the low temperature crystal were obtained.The fundamental frequencies for each of the two conformers, C1 and Cs, were assigned and the results checked by normal coordinate analysis. The same diagonal and off-diagonal force constants were employed for the two conformers and the force fields were derived by means of a least squares refinement, including data for chloroethane, 1,1-dichloroethane and various deuterated species. A standard deviation of 3 % was obtained in the final fit.From the changes in relative intensities for infrared bands belonging to the C1 and Cs conformers with increasing pressure, the volume differences (ΔV¯between the conformers were determined in CS2 solution and in the pure liquid.

Pressure effects on conformational equilibria. Difference in volume between conformers of 1,1,2-trichloroethane

The effect of pressure on the equilibrium between conformers of 1,1,2-trichlorocyclohexane has been studied using infrared spectra obtained with the diamond anvil cell. Changes in relative intensities of infrared bands show that the population of the more polar conformer (Cs symmetry) increases relative to that of the less polar conformer (C1 symmetry) with increasing pressure. Volume differences for converting the less polar to the more polar conformer are −3.8 cm3/mol in pure liquid and −1.8 cm3/mol in CS2 solution. These results are in agreement with values calculated by K. R. Crook and E. Wyn-Jones [J. Chem. Phys. 50, 3445 (1969)].

Resonance Raman spectra of Cu‐porphin‐d4(meso) and Ni‐porphin, and the infrared spectrum of Cu‐porphin‐d4

AbstractThe resonance Raman spectra are presented for Ni‐porphin and Cu‐porphin‐d4(meso) as dilute solutions in CS2 and C2Cl4 using an Ar+ laser and a tunable Rhodamine 6G dye laser. The Raman features are assigned to the different vibrational species on the basis of their depolarization data. The assignment of 14 features in the spectrum of Cu‐porphin‐d4 and 13 features in the spectrum of Cu‐porphin and Ni‐porphin is discussed by comparing the spectra of the three molecules. Also the infrared spectrum of Cu‐porphin‐d4 as a solid dispersed in CsI matrix is reported for the 200–2000 cm−1 region.

The infrared and Raman spectra of perchloro‐[4] ‐ radialene

AbstractInfrared and Raman spectra are reported for polycrystalline perchloro‐[4]‐radialene and for solutions in CCl4 and CS2. An earlier X‐ray structure determination by van Remoortere and Boer has shown that in the crystal the molecular symmetry is almost D2d (puckered ring), but is slightly distorted to C2. This distortion was attributed to crystal packing forces. The vibrational spectrum does not show the distortion. The spectra are essentially the same for polycrystalline solid as for solution, and are completely compatible with D2d in both states. Assignments are made for a few of the modes where evidence warrants it. Some observations are also made about the mass spectrum, which has a rich structure because of the many isotopic species.

Conformational equilibrium of 2-hydro-2-oxo-5,5-dimethyl-1,3,2-dioxaphosphorinane

A study was made of the conformational equilibrium of 2-hydro-2-oxo-5,5-dimethyl-l,3,2-dioxaphosphorinane in CCl4, CS2, C6H6, and C6H5Cl solutions, and the conformation energy of the oxygen of the phosphoryl group was determined.

Resonance Raman spectra of Cu-1:3:5:7-tetramethyl porphin and Cu-1:2:3:4:5:6:7:8-octamethyl porphin

Resonance Raman spectra of Cu-1:3:5:7-tetramethyl porphin and Cu-1:2:3:4:5:6:7:8-octamethyl porphin have been obtained both in dilute CS2 solution and as solids dispersed in KBr matrices using the Ar+ and tunable Rhodamine 6G dye lasers. The solution data for Cu-octamethyl porphin show that its rigorous molecular symmetry in solution is D4h, while the spectral data for Cu-tetramethyl porphin are consistent with C4h molecular symmetry. Assignments for some of the stronger bands are discussed by comparing the spectra of these two molecules with other planar metalloporphins and porphyrins.

Resonance Raman studies of 1,2,3,4,5,6,7,8‐octamethylporphin, 1,3,5,7‐tetramethylporphin, and mesotetraphenylporphin and its Ni‐, Cu‐, and Pd‐chelates

AbstractResonance Raman spectra are reported for 1,2,3,4,5,6,7,8‐octamethylporphin, 1,3,5,7‐tetramethylporphin and mesotetraphenylporphin and its Ni‐, Cu‐, and Pd‐chelates. Comparison of infrared and Raman data for the non‐metallo compounds provides evidence that mesotetraphenylporphin loses its centre of symmetry in the solid state while the other two molecules retain theirs.Depolarization ratio measurements for Ni‐tetraphenylporhin in CS2 solution reveal the presence of several anomalously polarized vibrations (ϱ > ¾). Evidence is presented to show that the symmetry of the molecule in solution has been reduced from D4h.

Studies of heterocyclic compounds. Part XVII. Synthesis of 1,6-Dioxa-6a-thia- and 1,6-dioxa-6a-selena-pentalenes

1,6-Dioxa-6a-thia- and 1,6-dioxa-6a-selena-pentalenes, two new classes of hypervalent heterocyclic compound, have been synthesised by the reaction of pyran-4-thiones and -4-selones, respectively, with thallium(III) trifluoroacetate, and treatment of the resulting labile thallium-containing pyrylium trifluoroacetates with water 1,6-Dioxa-6a-thiapentalene was also formed in low yield by ring-opening of pyran-4-thione with sodium hydroxide in aqueous dimethyl sulphoxide, and intramolecular oxidative coupling of the resulting anion with potassium ferricyanide. 1H N.m.r. spectra of symmetrically substituted 1,6-dioxa-6a-thia- and 1,6-dioxa-6a-selena-pentalenes show real or time averaged C2v symmetry. The pattern of the spectrum of 1,6-dioxa-6a-thiapentalene was unaffected by change of solvent (CDCl3, CS2, or CD3CN) or by lowering the temperature of a solution in CDCl3(to –50°) or CS2(to –90°). The i.r. spectra of 1,6-dioxa-6a-thiapentalene, 1,6-dioxa-6a-selenapentalene, and their 2,5-dimethyl derivatives show no absorption in the double bond region above 1515 cm–1. The significance of the 1H n.m.r. and i.r. spectra of 1,6-dioxa-6a-thia- and 1,6-dioxa-6a-selena-pentalenes is discussed in relation to structure. Thionation of 1,6-dioxa-6a-thiapentalene with phosphorus pentasulphide gave 6a-thiathiophthen. 1,6-Dioxa-6a-thiapentalene underwent sulphur–oxygen exchange in boiling thioacetic acid to give a mixture of 6a-thiathiophthen and 1-oxa-6,6a-dithiapentalene. Thionation of 1,6-dioxa-6a-selenapentalene with phosphorus pentasulphide afforded 6a-selenathiophthen.

Proton Magnetic Resonance Study of Conformational Equilibria of the Pyridinealdehydes in Solution. Comparison with Other Methods

A p.m.r. study of the pyridinealdehydes shows that accurate spectral analysis yields long-range spin–spin coupling constants which are a precise measure of the conformational equilibria in solution. Thus, in CS2 solution the ON-trans form of 2-pyridinealdehyde is more stable than the ON-cis form by at least 2.3 kcal/mol, while in acetone solution it is 1.6 kcal/mol more stable than the cis form. Classical solvation theory allows the conclusion that in the gas phase the trans form is more stable than the cis form by about 7 kcal/mol, in contradiction to the predictions of approximate MO theory at the INDO level. The trans form of 3-pyridinealdehyde is also more stable than the cis form in polar and in nonpolar solvents. The results are compared with those of other experiments on these equilibria.

Studies of heterocyclic compounds. Part XV. Synthesis and structure of 6a-thia-1,6-diazapentalenes (isothiazolo[5,1-e]isothiazoles)

Methylation of 6-methyl-1,6a-dithia-6-azapentalenes with methyl iodide occurs exclusively at sulphur (S-1). The resulting 2-methyl-5-(2-methylthiovinyl)isothiazolium iodides react with methylamine to give symmetrical 6a-thia-1,6-diazapentalenes, a new class of hypervalent heterocyclic compound. 4,5-Dihydro-1,7-dimethyl-3H-benzo[cd]-6a-thia-1,6-diazapentalene and 1,2,5,6-tetramethyl-6a-thia-1,6-diazapentalene were accompanied by small quantities of thiones which result from reductive cleavage of the S–N bond in the 2-methyl-5-(2-methylthiovinyl)isothiazolium cations. 1,6-Dimethyl- and 1,3,4,6-tetramethyl-6a-thia-1,6-diazapentalene were accompanied by the corresponding 6-methyl-1,6a-dithia-6-azapentalenes fromed by S-demethylation of the 2-methyl-5-(2-methylthiovinyl)isothiazolium cations. 1H N.m.r. spectral studies show that symmetrically substituted 6a-thia-1,6-diazapentalenes in solution possess real or time-averaged C2v symmetry. The pattern of the spectrum of 1,3,4,6-tetramethyl-6a-thia-1,6-diazapentalene was unaffected by change of solvent [CDCl3, CS2, or (CD3)2SO] or by lowering the temperature of a solution in CS2 to –70°. The significance of the 1H n.m.r. spectra of 6a-thia-1,6-diazapentalenes and analogues of 6a-thiathiophthens is discussed in relation to structure. 6a-Thia-1,6-diazapentalenes form stable charge-transfer complexes with 1,3,5-trinitrobenzene.

The vibrational spectra of 1,4-telluroxan

The i.r. spectra of 1,4-telluroxan were recorded in the vapour, liquid, amorphous and crystalline states between 4000 and 200 cm −1 whereas a far infrared spectrum of a CS 2-solution was extended to 50 cm −1. Raman spectra of the liquid, amorphous and crystalline states were obtained and semiquantitative polarization measurements were calculated. A force field calculation was made, and the fundamental frequencies were assigned in terms of C s molecular symmetry. The vibrational spectra of 1,4-thioxan, 1,4-selenoxan, 1,4-telluroxan, 1,4-thioselenan, 1,4-dioxan, 1,4-dithian and 1,4-diselenan are closely related and various correlations have been pointed out.

Étude de la répartition des dislocations dans un monocristal de soufre alpha par topographies aux rayons x

Large single crystals of orthorhombic sulphur have been grown from a CS2 solution. Most of the dislocations form bundles originating at the seed and lie roughly normal to the major growth faces. The remaining parts of the crystal are practically dislocation-free. Most common Burgers vectors are 12[110] and 12[1ovbar|10] which can be easily interpreted from the atomic structure.