Of cresol isomers

A simulated moving bed system has been proposed for the production of p-cresol from mixtures of cresol isomers even derived from coal tar [52]. Neuzil et al. give details of the development of the adsorbent and desorbent system reviewing balancing mass transfer issues with selechvity [53]. The desorbent for the cresol system is 1-pentanol. For these Hquid adsorptive systems where highly polar molecules are adsorbed and desorbed with polar desorbents, the tolerance of the system for trace polar contaminants is higher because the feed and desorbent can more easily exchange with them on the surface of the zeolites. 

Since before World War II, multimillion pound quantities of cresols have been produced annually in the United States (O Brochta 1949), and domestic production and sales of cresols have steadily increased in recent years. Approximately 57.3 (USITC 1986), 73.3 (USITC 1988), and 82.3 (USITC 1989) million pounds of cresols were produced annually in the United States in 1986, 1987, and 1988, respectively. Respective sales were 56.6 (USITC 1986), 66.8 (USITC 1988), and 72.1 (USITC 1989) million pounds. These production totals include data on the manufacture of cresylic acid and exclude information on cresol production by coke and gas-retort ovens. The commercial mixture of cresol isomers, in which the m-isomer predominates and contains less than 5% phenol, is sometimes referred to as cresylic acid (Windholz et al. 1983). However, cresylic acids generally are composed of cresols, phenols, and xylenols they are defined as those mixtures in which over 50% will boil at temperatures above 204 C (Sax and Lewis 1987). In 1987, the national capacity for producing cresylics was 208 million pounds per year (CMR 1987). Information regarding the production levels of individual isomers and specific mixtures was unavailable. 

Smolenski WJ, Suflita JM. 1987. Biodegradation of cresol isomers in anoxic aquifers. Appl Environ Microbiol 58 710-716. 

Tembreull R, Lubman DM. 1984. Use of resonant two-photon ionization with supersonic beam mass spectrometry in the discrimination of cresol isomers. Anal Chem 56(11) 1962-1967. 

Research has also been aimed at the development of more-transparent base-soluble matrix resins. For example, novolacs prepared from pure p-cresol absorb less strongly at 250 nm than do typical photoresist novolacs containing a mixture of cresol isomers. Unfortunately, p-cresol novolac is only sparingly soluble in aqueous base and has limited usefulness (28, 57). Other examples of more-transparent matrix resins include poly(dimethyl glutarimide) (PMGI) (58) and copolymers of methyl methacrylate (MMA) and methacrylic acid (MAA) [P(MMA-MAA)]. 

Cresol consists of a mixture of cresol isomers, predominantly m-cresol, and other phenols obtained from coal tar or petroleum. It is a colorless, yellowish to pale brownish-yellow, or pink-colored liquid, with a characteristic odor similar to phenol but more tarlike. An aqueous solution has a pungent taste. 

Atmospheric fate Cresols are not expected to persist in the atmosphere because (1) cresols have low estimated half-lives (less than 1 day) (2) they are sensitive to photolysis and (3) the water solubility of cresols may cause transport of cresols from the atmosphere to the soil or aqueous environment. The photodegradation half-life of cresol isomers during the daytime is 8-10 h while at night it is 2 min. Daytime half-lives would be reduced under smog conditions. Cresols are highly soluble compounds, and gas scavenging will be an efficient removal process as is reflected by high concentrations in rain. 

The addition of OH to toluene can be thought to occur at the position of ipso (carbon atom bonded to the methyl group), ortho (carbon atom adjacent to the methyl group), meta (one carbon apart from the methyl group), and para (opposite carbon to the methyl group). Actually, the OH addition reaction occurs predominantly to the ortho position followed by to the para position (ortho-para orientation), which has been confirmed by the yields of cresol isomers (Smith et al. 1998 Klotz et al. 1998), and also by supported by theoretical calculations (Bartolotti and Edney 1995 Suh et al. 2002). The reaction of cyclohexadienyl radicals with O2 in the atmosphere will be described in Sect. (7.2.8). 

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