Phenol limit values

Phenol. Phenol monomer is highly toxic and absorption by the skin can cause severe blistering. Large quantities can cause paralysis of the central nervous system and death. Ingestion of minor amounts may damage kidneys, Hver, and pancreas. Inhalation can cause headaches, dizziness, vomiting, and heart failure. The threshold limit value (TLV) for phenol is 5 ppm. The health and environmental risks of phenol and alkylated phenols, such as cresols and butylphenols, have been reviewed (66). 

The actual limit value of rr, below which the time constraint is met for a given transducer, is somewhat ambiguous. For a 0.5 MHz transducer (response time 2 xs), Mulder et al. [297] set this limit at 60 ns, based on the observation of a maximum of amplitude of the photoacoustic wave with the concentration of phenol and calculating rr from the rate constant of reaction 13.24, k = 3.3 x 108 mol-1 dm3 s-1 [298]. Later, Wayner et al. [293] empirically choose 100 ns as that limit and used laser flash photolysis results to adjust the phenol concentration until the lifetime of reaction 13.24 was less than that limit. In any case, the safest way of ensuring that the time constraint is being met is to verify it experimentally by varying the concentration of substrate until the observed waveform reaches a maximum (or, equivalently, until the final A0bs77 value reaches a maximum). 

The 2003 ACGIH threshold limit value-time-weighted average (TLV-TWA) for phenol is 5 ppm (19mg/m ) with a notation for skin absorption. 

The American Conference of Governmental Industrial Hygienists (ACGIH) (1997) has recommended 19 mg/m as the threshold limit value for occupational exposures to phenol in workplace air. Similar values have been used as standards or guidelines in many countries (International Labour Office, 1991). 

For the stronger proton acceptors (ammonia, monoethylamine, and piperidine) a relation between the B proton affinities and the spectral shifts of the S3 <- S0 states of phenol(B) or naphthol(B) shows a linear dependence for proton affinities lower than a limit value situated around 10.4 eV (s240 kcal mol-1) for both phenol or naphthol molecules. Above this limit, the spectral shift is much larger and is different for phenol and 1-naphthol (see Figure 4-17). Nevetheless, this limit seems to correspond with the energetical limit of the proton transfer reaction. 

The hindered phenolics are primary antioxidants and are normally used in conjunction with the thiodipropionate esters. These combinations are synergistic. They are of only limited value as heat stabilizers when used alone the thiodipropionate esters are secondary antioxidants, also of only limited value when used alone. 

Similar Bronsted exponents, 0.94 0.02 for phenolate ions and 0.98 0.08 for secondary amines, were observed but the Bronsted plots for these two types of catalyst were separated by about half a unit in log 0 k. The values of the Bronsted exponents are close to the limiting values of unity expected for normal proton transfer. Reaction (78) is thermodynamically favourable in the reverse direction and for fully normal proton transfer the rate coefficients for recombination of the carbanions with phenols and ammonium ions should be around 101 0 1 mole"1 sec"1. Calculations using the approximate pif 21 for this acid measured [69] in dimethyl... 

Paper chromatography was another popular method of studying organic water constituents (Shapiro, 1957 Packham, 1964 Midwood and Felbeck, 1968) and also was of limited value in characterizing humic substances and colored organic acids, because the complex mixtures often produced broad diffuse bands and streaks. Some of the spot-tests and chromatograms of Shapiro (1957) demonstrated the presence of colorless acids and suggested the presence of phenols and enols. 

However, the overall phenol conversion values were lower (as compared to TS-1) which may be mainly due to small pore size of NU-1 zeolite and the larger reactants have limited access to the inner channels. Furthermore, the catalytic activity may be due to sonje surface active species formed after calcination as an impurity anatase phase The data on IR, UV-vis, TG/DTA and XRD are found to compliment these results. 

The Pfeiffer effect, the outer-sphere interaction of a chiral substrate with a rapidly interconverting racemic solution of a chiral lanthanide complex, can be investigated by measurement of the luminescence dissymmetry factor (the ratio of circularly polarized luminescence to total luminescence) for Eu or Tb " complexes. Thus the racemic D chiral complexes [M(dpa)3], where M = Eu or Tb, interact in an outer-sphere manner with the following optically active spiecies cationic chiral transition metal complexes, ascorbic acid, aminocarboxylates, tartrates, amines and phenols. Association constants can be obtained from limiting values of the dissymmetry factors. In some cases, inner-sphere complexation can be demonstrated, as judged by changes in the general nature of the circularly polarized luminescence spectrum and pH irreversibility of the complexation. 

Phenol and (thiophenol)FeCp complexes were prepared by substitution for Cl by OH- and SH- nucleophiles. Alcohols are initially converted to alkoxides using a base such as KOt-Bu or NaH and then give smooth substitution [63,64]. Both aryl and alkyl thiols react smoothly using K2CO3 as a base [65]. Substitution with selenium nucleophiles is also known [66]. Primary and secondary amines are sufficiently reactive without added base if used in excess, although a base (e.g., Et3N, pyridine or K2CO3) can be used to drive the reaction [67-69]. Mild reaction conditions allow arylation of amino acids with (PhF)FeCp (Eq. 17) [69]. The process is of limited value, however, since decomplexation of the arene led to decomposition. 

ACGIH. 1986. Documentation of the Threshold Limit Values and Biological Exposure Indices, 5th ed. Cincinnati, OH American Conference of Governmental Industrial Hygienists. Agrawal, H. P. 1987. Evaluation of the toxicity of phenol and sodium pentachlorophenate to the snail Indoplanorbis (Deshayes). J. 

In phenolic compound analysis FIA is the preferred method rather than conventional chromatographic and spectrometric methods because it offers lower detection limit values, greater sensitivity, short time requirement, lower sample requirement, an easy technique, user-friendliness, and high linearity, recovery, and precision. This system represents a new contribution in the field of automation of analytical methods. 

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