Aromatic hydrocarbons indenes

The first resins to be produced on a commercial scale were the coumarone—indene or coal-tar resins (1) production in the United States was started before 1920. These resins were dominant until the development of petroleum resins, which were estabHshed as important raw materials by the mid-1940s. Continued development of petroleum-based resins has led to a wide variety of aHphatic, cyclodiene, and aromatic hydrocarbon-based resins. The principal components of petroleum resins are based on piperylenes, dicyclopentadiene (DCPD), styrene, indene, and their respective alkylated derivatives. 

The polymerization process of coal tar and petroleum fraction (from which aromatic hydrocarbon resins are obtained) are similar. The process is extensively described in the book by Mildenberg et al. [25]. There are three basic steps in the polymerization of coumarone-indene and hydrocarbon resins. 

Aromatic hydrocarbon resins. The polymerization procedure and variables in the reactions of the aromatic hydrocarbon resins are similar to those for the coumarone-indene resins. However, the Cg feedstreams used in the polymerization of the aromatic hydrocarbon resins do not contain significant amounts of phenols or pyridine bases, so they are submitted directly to fractional distillation. Distillation produced more byproducts than light coal-tar oils. The aromatic hydrocarbon resins obtained have softening points between liquid and 125°C and Gardner colour of 6 to 11. By changing distillation conditions, aromatic hydrocarbon resins with softening points between 65 and 170°C and Gardner colour of 5 to 10 can also be obtained. 

Tackifiers. SBRs have poor tack, so addition of tackifiers is necessary. The tackifier increases the wetting of the adhesive and also increases the glass transition temperature of the adhesive. Typical tackifiers for SBR adhesives are rosins, aromatic hydrocarbon resins, alpha-pinene, coumarone-indene and phenolic resins. 

The highly aromatic resins are often used as coumarone/indene resin substitutes. A range of soft aromatic resins is available, produced from the alkylation of xylene and other aromatic hydrocarbons with dicyclopentadiene. These are excellent softeners for a wide range of rubbers. In common with other aromatic materials derived from petroleum sources, some of the resins used within the rubber industry are deemed to be carcinogenic. 

Not much is known about the opening of dihalocyclopropanes by Lewis acids beyond reports on the reaction of dibromo- and dichloro-cyclopropanes with aromatic hydrocarbons under the influence of AlCb or FeCb leading to indenes.229"231... 

The efficiency of nucleophilic addition of methanol to the radical cation of arylalkenes can be improved by use of a redox sensitizer system, and also by utilizing solvent and additive effects. Pac and his coworkers found that the aromatic hydrocarbon-electron acceptor sensitizer system, such as phenan-threne-p-dicyanobenzene system, acts as an excellent redox sensitizer for the anti-Markownikoff addition of methanol to 1,1-diphenylethene and indene (Scheme 7) [29]. 

Majima, T., Pac, C., Nakasone, A., Sakurai, H., Redox photosensitized Reactions. 7. Aromatic Hydrocarbon photosensitized Electron transfer Reactions of Furan, Methylated Furans,l,l Diphenylethylene, and Indene with p Dicyanobenzene J. Am. Chem. Soc. 1981, 103, 4499 4508. 

Polycyclic Aromatics. Extensive replacement of hydrogen by lithium in polycyclic aromatic hydrocarbons has been demonstrated by Halasa (15). Anthracene, biphenyl, fluorene, indene, and ferrocene (16) undergo polymetalation by n-butyllithium—TMEDA in hexane at 70°C for 24 hours. The products are insoluble mixtures of polylithio compounds containing up to 10 lithium atoms per molecule. Derivatization was accomplished using both D20 and trimethylchlorosilane and by analyzing the mixture of deuterated or silylated products by mass spectrometry. The results for anthracene, which are typical, appear in Table I. 

Badger, G.M. and R.W.L. Kimber The formation of aromatic hydrocarbons at high temperatures. Part Vt. The pyrolysis of tetralin J. Chem. Soc. (1960) 266-270. Badger, G.M. and R.W.L. Kimber The formation of aromatic hydrocarbons at high temperatures. Part Vll. The pyrolysis of indene J. Chem. Soc. (1960) 2746-2749. Badger, G.M., R.W.L. Kimber, and J. Novomy The formation of aromatic hydrocarbons at high temperatures. 

OTHER COMMENTS coal tar naphtha is a mixture of aromatic hydrocarbons, mainly toluene, xylene, and cumene however, those coal tar naphthas with low boiling points contain appreciable amounts of benzene used as a diluent in coatings, inks, paints, resins, and cements used in the preparation of coumarone and indene utilized as a solvent in the rubber industry utilized in formulations of nitrocellulose and ethyl cellulose. 

The structural element of a coumarone-indene resin is relatively similar to that for aromatic hydrocarbon resins, as they differ only in the proportion of indene-type structures which are present in higher concentration in the coumarone-indene resins. The main monomers in the aromatic resins are styrene and indene. Styrene produces the atactic conformation of the resins, whereas indene introduces rigidity into the polymer chain. A typical structural element of an aromatic resin is given in Fig. 11. 

The sorption efficiency of light aromatic hydrocarbon tars has been found to depend on whether they are hydrophilic or hydrophobic. On scrubbing with pure water, it has been observed that only phenol is removed - phenol being polar, for example hydrophilic. Whereas the other light aromatic hydrocarbon tars - benzene, toluene, xylene, styrene and indene - are non-polar hydrophobic compounds. 

In flames of alaphatic hydrocarbons (also oxygen-containing compounds such as ethanol) unsaturated (usually alaphatic) hydrocarbons of higher molecular weight than the initial fuel molecule are found. With benzene (and presumably other aromatic hydrocarbon flames) derivatives such as napthalene, indene, etc., are formed. All of these intermediates disappear by the end of the primary reaction zone with the exception of the polyacetylenes (C2 H2). They (the polyacetylenes) are formed relatively late in the primary reaction zone and in the case of alaphatic hydrocarbons acetylene is their precursor. The concentration measurements indicated that in this region the polyacetylenes were in equilibrium with one another, hydrogen, and acetylene, e.g.. 

There are difficulties in linking these measurements to pK scales in aqueous solution, and the absolute values obtained are therefore subject to uncertainty, but there is no doubt that aromatic hydrocarbons containing extensive Ti-electron systems are much stronger acids than the paraffins. Typical values are pX(triphenylmethane) = 27-33, pK(fluo-rene) = 20-23, pX(indene) = 18-23. In these and similar cases we may consider that the anion is stabilized by a distribution of the negative charge over a number of atoms, which can be formally represented by writing a number of resonance structures. Thus for the anion of triphenylmethane we can write... 

Knox et al. [108] studied the retention characteristics of 54 aromatic hydrocarbons (benzene— hexamethylbenzene and selected isomers, toluene—decyl-benzene and selected isomers, indane, indene, tetrahydronaphthalene, and naphthalene—fluorene and terphenyls) on three Cjg columns using 70/30, 80/20, and 90/10 (w/w) methanol/water mobile phases, (Note that the v/v ratios are q)proxi-mately 74/26, 83/17 and 92/8, respectively.) Capacity factors were tabulated for each column and each mobile phase composition when the analytes eluted with a k = 40. The t values ranged from 1 (benzene) to 39 (1,2,3-triisopropylbenzene) for 70/30 and 0.2 (benzene) to 20 ( -tridecylbenzene) for 90/10 methanol/ water. 

Lu, M. 2001. Aromatic hydrocarbon growth from indene. Chemosphere 42(6) 625-633. 

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