O-Vinyltoluene

The Pd-catalyzed coupling reaction of an aryl halide and olefin is a very efficient and practical method for making C—C bonds. The Heck alkenylation of aryl bromides with ethylene was used by Dow Chemical to make high-purity 2- and 4-vinyltoluenes, which are of interest as co-monomers in styrene polymers [159]. The monomer, o-vinyltoluene (99), has a low toxicity and an attractive co-monomer for styrene polymers. o-Vinyltoluene improved heat distortion properties of styrene and polymerization rate. It also minimized color formation or cross-linking and it was difficult to make by other routes [159]. Catalyst turnover, rate, and lifetime were significantly improved. 

Ethyltoluene is manufactured by aluminum chloride-cataly2ed alkylation similar to that used for ethylbenzene production. All three isomers are formed. A typical analysis of the reactor effluent is shown in Table 9. After the unconverted toluene and light by-products are removed, the mixture of ethyltoluene isomers and polyethyltoluenes is fractionated to recover the meta and para isomers (bp 161.3 and 162.0°C, respectively) as the overhead product, which typically contains 0.2% or less ortho isomer (bp 165.1°C). This isomer separation is difficult but essential because (9-ethyltoluene undergoes ring closure to form indan and indene in the subsequent dehydrogenation process. These compounds are even more difficult to remove from vinyltoluene, and their presence in the monomer results in inferior polymers. The o-ethyltoluene and polyethyltoluenes are recovered and recycled to the reactor for isomerization and transalkylation to produce more ethyltoluenes. Fina uses a zeoHte-catalyzed vapor-phase alkylation process to produce ethyltoluenes. 

Note Normally inhibited with 8-12 ppm 4-7er7-butylcatechol to prevent polymerization. According to Chevron Phillips Company (March 2002), 99.93% styrene contains the following components (ppm) benzene (<1), toluene (<1), ethylbenzene (50), a-meth ylstyrene (175), m + p-xylene (120), o-xylene (125), isopropylbenzene (100), / -propylbenzene (60), m + p-ethyltoluene (20), vinyltoluene (10), phenylacetylene (50), m + p-divinylbenzene (<10), o-divinylbenzene (<5), aldehydes as benzaldehyde (15), and peroxides as benzoyl-peroxides (5). 

Despite the fact that aryl bromides are generally less reactive, o- and p-bromotoluenes could be efficiently vinylated with ethene in DMF/H2O with [Pd(OAc)2] + P(o-tolyl)3 as catalyst and Et3N as base [16]. With careful choice of reaction parameters (90 °C and 6 bar of ethene) all bromotoluene was converted to high purity ortho- or para-vinyltoluene. Under the conditions used, the reaction mixture forms two phases. In this case the main role of water is probably the dissolution of triethylamine hydrobromide which otherwise precipitates from a purely organic reaction medium and causes mechanical problems with stirring. 

The application of ethylene in Heck reactions often shows different activities from other alkenes, because of Wacker-type side reactions. It was found, however, that iodo- and acceptor-substituted bromoarenes are cleanly converted in aqueous media to the corresponding styrenes utilizing a palladium-TPPMS complex [13], Furthermore, high purity o- and p-vinyltoluenes were prepared on a large scale (in... 

Fig. 6.1. Gas chromatogram of a mixture of hydrocarbons. Stationary phase (A) 15% water on Chromosorb P (B) 25% aqueous solution of 3.5 Af AgNO, and 0.05 Af HgfNO,), onChromosorb P (C) 50% aqueous solution of 5.0Af AgNO, and 0.05 Af Hg(NOj)2 on Chromosorb P. Compounds (A) 1 = methane 2 = methylcyclohexene 3 = nonane 4 = benzene 5 = toluene 6 = decane 7 = p-xylene 8 = o-xylene 9 = undecane 10 = vinyltoluene (B) 1 = methane 2 = nonane 3 = decane 4 = benzene 5 = toluene 6 = p-xylene 7 = undecane 8 = o-xylene (C) 1 = methane 2 = decane 3 = undecane 4 = dodecane 5 = benzene. Reprinted with permission from ref. 45.

Fig. 8. Thermogravimetric analysis of polymers and copolymers of styrene in nitrogen at 10°C/min A represents PS B, poly(vinyltoluene) C, poly(a-methylstyrene) D, p oly (s tyrene- co- acryl o nit rile), with 71.5% styrene E, poly(styrene- o-butadiene), with 80% styrene and F,...

Methyl and stearyl dimethylaminoethyl methacrylate quatemized with dimethyl sulfate. See Polyquatemium-8 Methyi-Steriiine. See Methylparaben Methylstyrene. See Vinyltoluene monomer a-Methylstyrene. See o-Methylstyrene monomer... 

Polyethylene, linear low density film, food-contact Polyvinyl alcohol film, food-contact polyolefin o-Methylstyrene/vinyltoluene copolymer, hydrogenated film, food-contact PP Terpene resin film, food-packaging Ethylene/ethyl acrylate copolymer Ethylene/methyl acrylate copolymer 1,2-Polybutadiene Polystyrene Silica, fumed Vinylidene chloride/methyl acrylate copolymer film, food-packaging pressure-sensitive adhesives... 

The demand for vinyltoluene is considerably higher than that for divinylbenzene, reaching around 30,000 to 35,000 tpa. Ethyltoluene is used as a raw material. It is produced by Friedel-Crafts alkylation of toluene with ethylene in the presence of AICI3 at 80 °C in the liquid phase, or in the gas phase, using zeolite catalysts. During the refining operation, care must be taken to ensure that the o-ethyl-... 

The reaction data are summarized in Table 4.4. With unmodified H — ZSM-5 zeolite catalyst, near equilibrium ratio of the meta and para isomers was observed. However, lower than equUibrium amounts of o-ethyltoluene were produced. A dramatic increase in selectivity compared with unmodified catalysts was obtained for the para isomer (up to 98%). A corresponding decrease in meta isomer and virtual elimination of 0-ethyltoluene was also observed. Thus, a completely different isomeric mixture ofethyltoluenes was obtained with modified ZSM-5 zeolites compared with HCl/AlCb catalyst presently used for commercial vinyltoluene production. 

This test method will detect the following impurities non-aromatic hydrocarbons containing ten carbons or less, ethylbenzene, p- and m-xylene, cumene, o-xylene, n-propylbenzene, m- and p-ethyltoluene, alpha-methyl-styrene, m- and p-vinyltoluene and others where specific impurity standards are available. Absolute purity cannot be determined if unknown impurities are present. 

---