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Sulfur branched

Channels in crystals of thiourea [62-56-6] (87) are comparable but, as a consequence of the larger size of the sulfur atom, have larger cross-sectional areas (0.7 nm) and can trap branched-chain, aUcychc, and other molecules of similar dimensions including polychlorinated hydrocarbons. But they do not include the straight-chain hydrocarbons that work so well with urea. [Pg.69]

Thiuram Sulfides. These compounds, (8) and (9), are an important class of accelerator. Thiurams are produced by the oxidation of sodium dithiocarbamates. The di- and polysulfides can donate one or more atoms of sulfur from their molecular stmcture for vulcanization. The use of these compounds at relatively high levels with litde or no elemental sulfur provides articles with improved heat resistance. The short-chain (methyl and ethyl) thiurams and dithiocarbamates ate priced 2/kg. Producers have introduced ultra-accelerators based on longer-chain and branched-chain amines that are less volatile and less toxic. This development is also motivated by a desire to rninirnize airborne nitrosamines. [Pg.222]

For increased solubiHty to prevent bloom, shorter-chain carboxyHc acids or zinc carboxylates can be substituted. The use of chain-branched carboxyHc acids reduces the tendency for the formulations to lose sulfur cross-links or revert upon prolonged heating (7). Translucent articles such as crepe soles can use a zinc carboxylate or employ zinc carbonate as a transparent zinc oxide. [Pg.225]

Fig. 1. Sulfonated and sulfated acid products viscosities after 98% conversions at varying temperatures where the vertical line indicates the maximum temperature for batch sulfonation using SO to minimi2e color deterioration lines A—C represent branched C 2 alkyl ben2ene (BAB) sulfonic acid from SO, oleum (settied), and oleum (whole mixture), respectively lines D and E, lauryl alcohol 3-ethoxylate sulfuric ester (SO ) and lauryl alcohol sulfuric ester... Fig. 1. Sulfonated and sulfated acid products viscosities after 98% conversions at varying temperatures where the vertical line indicates the maximum temperature for batch sulfonation using SO to minimi2e color deterioration lines A—C represent branched C 2 alkyl ben2ene (BAB) sulfonic acid from SO, oleum (settied), and oleum (whole mixture), respectively lines D and E, lauryl alcohol 3-ethoxylate sulfuric ester (SO ) and lauryl alcohol sulfuric ester...
Investigation of Immedial Orange C, Cl Sulfur Orange 1 [1326-49 ] (Cl 53050), produced from 2,4-diaminotoluene (MTD) revealed ca 6—8 mols of MTD linked by thiazole rings. Whether the linkage is linear (5) or branched (6) was not ascertained with certainty but again showed that the thiazole chromophore is present. [Pg.163]

Alkylate. Alkylation means the chemical combination of isobutane with any one or a combination of propylene, butylenes, and amylenes to produce a mixture of highly branched paraffins that have high antiknock properties with good stabiUty. These reactions are cataly2ed by strong acids such as sulfuric or hydrofluoric acid and have been studied extensively (98—103). In the United States mostly butylenes and propylene are used as the olefins. [Pg.370]

Feedstocks. Feedstocks are viscous aromatic hydrocarbons consisting of branched polynuclear aromatics with smaller quantities of paraffins and unsaturates. Preferred feedstocks are high in aromaticity, free of coke and other gritty materials, and contain low concentrations of asphaltenes, sulfur, and alkah metals. Other limitations are the quantities available on a long-term basis, uniformity, ease of transportation, and cost. The abiUty to handle such oils in tanks, pumps, transfer lines, and spray nozzles are also primary requirements. [Pg.544]

Highly Branched Acids. These acids, called neoacids, are produced from highly branched olefins, carbon monoxide, and an acid catalyst such as sulfuric acid, hydrogen fluoride, or boron trifluoride. 2,2,2-Trimethylacetic acid (pivaUc acid) is made from isobutylene and neodecanoic acid is produced from propylene trimer (see Carboxylic Acids, trialkylacetic acids). [Pg.92]

Carbonylation, or the Koch reaction, can be represented by the same equation as for hydrocarboxylation. The catalyst is H2SO4. A mixture of C-19 dicarboxyhc acids results due to extensive isomerization of the double bond. Methyl-branched isomers are formed by rearrangement of the intermediate carbonium ions. Reaction of oleic acid with carbon monoxide at 4.6 MPa (45 atm) using 97% sulfuric acid gives an 83% yield of the C-19 dicarboxyhc acid (82). Further optimization of the reaction has been reported along with physical data of the various C-19 dibasic acids produced. The mixture of C-19 acids was found to contain approximately 25% secondary carboxyl and 75% tertiary carboxyl groups. As expected, the tertiary carboxyl was found to be very difficult to esterify (80,83). [Pg.63]

Impurities can sometimes be removed by conversion to derivatives under conditions where the major component does not react or reacts much more slowly. For example, normal (straight-chain) paraffins can be freed from unsaturated and branched-chain components by taking advantage of the greater reactivity of the latter with chlorosulfonic acid or bromine. Similarly, the preferential nitration of aromatic hydrocarbons can be used to remove e.g. benzene or toluene from cyclohexane by shaking for several hours with a mixture of concentrated nitric acid (25%), sulfuric acid (58%), and water (17%). [Pg.60]

There are notable differences in both structures and stabilities for binary N-O and S-N anions (Section 5.4). The most common oxo-anions of nitrogen are the nitrite [N02] and the nitrate anion [NOs] the latter has a branched chain structure 1.1. The sulfur analogue of nitrite is... [Pg.2]

Although the structure of [SsN] has not been established by X-ray crystallography, the vibrational spectra of 30% N-enriched [SsN] suggest an unbranched [SNSS] (5.22) arrangement of atoms in contrast to the branched structure (Dsh) of the isoelectronic [CSs] and the isovalent [NOs] ion (Section 1.2). Mass spectrometric experiments also support the SNSS connectivity in the gas phase.Many metal complexes are known in which the [SsN] ion is chelated to the metal by two sulfur atoms (Section 7.3.3). Indeed the first such complex, Ni(S3N)2, was reported more than twenty years before the discovery of the anion. It was isolated as a very minor product from the reaction of NiCl2 and S4N4 in methanol. However, some of these complexes, e.g., Cu and Ag complexes, may be obtained by metathetical reactions between the [S3N] ion and metal halides. [Pg.100]

Using the first-principles molecular-dynamics simulation, Munejiri, Shimojo and Hoshino studied the structure of liquid sulfur at 400 K, below the polymerization temperature [79]. They found that some of the Ss ring molecules homolytically open up on excitation of one electron from the HOMO to the LUMO. The chain-like diradicals S " thus generated partly recombine intramolecularly with formation of a branched Sy=S species rather than cyclo-Ss- Furthermore, the authors showed that photo-induced polymerization occurs in liquid sulfur when the Ss chains or Sy=S species are close to each other at their end. The mechanism of polymerization of sulfur remains a challenging problem for further theoretical work. [Pg.15]

At all temperatures liquid sulfur consists of a complex mixture of all homocycles from Ss to at least S35 and of larger polymeric molecules of cyclic and chain-like structure (collectively termed as Sqo) [34]. At temperatures above 250 °C smaller molecules such as S5, S4, S3, and S2 are also likely components of the liquid as the composition of the equilibrium vapor demonstrates [9] (see above). In addition, branched rings and chains are probably minor components at temperatures near the boiling point of 445 °C [35] (see below). [Pg.36]

In addition to the chain-like and cyclic species discussed so far the presence of branched rings and chains in sulfur vapor and in liquid sulfur has been discussed [46] but no conclusive experimental evidence for such iso-... [Pg.37]

The concentration of this species in liquid sulfur was estimated from the calculated Gibbs energy of formation as ca. 1% of all Ss species at the boihng point [35]. In this context it is interesting to note that the structurally related homocyclic sulfur oxide Sy=0 is known as a pure compound and has been characterized by X-ray crystallography and vibrational spectroscopy [48, 49]. Similarly, branched long chains of the type -S-S-S(=S)-S-S- must be components of the polymeric S o present in liquid sulfur at higher temperatures since the model compound H-S-S-S(=S)-S-S-H was calculated to be by only 53 kJ mol less stable at the G3X(MP2) level than the unbranched helical isomer of HySs [35]. [Pg.38]

In addition to the branched rings and chains, cyclic Ss conformations of lower symmetry than Did are also likely components of liquid sulfur. For example, the following exo-endo isomer of Ss (Cs symmetry) is by just 28 kJ mor (AG°29s) less stable than the ground state conformation and therefore its relative concentration in liquid sulfur and sulfur vapor at the boiling point will also be 1% of all Ss species [35]. [Pg.38]

The HOMO/LUMO gaps of these isomeric sulfur molecules of branched rings and chains are considerably smaller than that of the crown-shaped Ss ring [35]. Therefore, the UV-Vis spectra of these species are expected to exhibit absorption bands at longer wavelengths than the ground state structure... [Pg.38]

Only the structures of di- and trisulfane have been determined experimentally. For a number of other sulfanes structural information is available from theoretical calculations using either density functional theory or ab initio molecular orbital theory. In all cases the unbranched chain has been confirmed as the most stable structure but these chains can exist as different ro-tamers and, in some cases, as enantiomers. However, by theoretical methods information about the structures and stabilities of additional isomeric sul-fane molecules with branched sulfur chains and cluster-like structures was obtained which were identified as local minima on the potential energy hypersurface (see later). [Pg.108]

By ab initio MO and density functional theoretical (DPT) calculations it has been shown that the branched isomers of the sulfanes are local minima on the particular potential energy hypersurface. In the case of disulfane the thiosulfoxide isomer H2S=S of Cg symmetry is by 138 kj mol less stable than the chain-like molecule of C2 symmetry at the QCISD(T)/6-31+G // MP2/6-31G level of theory at 0 K [49]. At the MP2/6-311G //MP2/6-3110 level the energy difference is 143 kJ mol" and the activation energy for the isomerization is 210 kJ mol at 0 K [50]. Somewhat smaller values (117/195 kJ mor ) have been calculated with the more elaborate CCSD(T)/ ANO-L method [50]. The high barrier of ca. 80 kJ mol" for the isomerization of the pyramidal H2S=S back to the screw-like disulfane structure means that the thiosulfoxide, once it has been formed, will not decompose in an unimolecular reaction at low temperature, e.g., in a matrix-isolation experiment. The transition state structure is characterized by a hydrogen atom bridging the two sulfur atoms. [Pg.111]

Smith DK, Diederich F (2000) Supramolecular Dendrimer Chemistry - A Journey Through the Branched Architecture. 210 183-227 Stec WJ, see Guga P (2002) 220 169-200 Steudel R (2003) Aqueous Sulfur Sols. 230 153-166 Steudel R (2003) Liquid Sulfur. 230 80-116... [Pg.238]


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See also in sourсe #XX -- [ Pg.128 ]




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Sulfur chain branched

Sulfur ring branched

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