Chlorinated phenols obtained

Dichlorophenols. Among all the dichlorophenols, C H Cl O, it is 2,4-dichlorophenol that is produced in greatest quantity. 2,4-Dichlorophenol is used in manufacturing 2,4-dichlorophenoxyacetic acid [94-75-7] (2,4-D) and 2-(2,4-dichlorophenoxy)propionic acid [720-36-5] (2,4-DP). Industrially, 2,4-dichlorophenol can be obtained by chlorinating phenol, -chlorophenol, o-chlorophenol, or a mixture of these compounds in cast-iron reactors. The chlorinating agent may be chlorine or sulfuryl chloride in combination with a Lewis acid. For example ... 

The chlorinated phenol and chlorinated biphenyls were not measured in the humic portion of the experiment because of losses from the base extraction procedure. b Caffeine data are from Experiment 2. c Insufficient data were obtained for ANOV procedure. 

On further photolysis, aldehydes, acids, and CO2 could be obtained. Selectivity was attained within a series of chlorinated phenols [122], and the rate of phenol oxidation depended on the coadsorption of Fe + or Ag+ onto the surface of the photocatalyst [123]. 

Chlorinated phenolic compounds in air-dried sediments collected downstream of chlorine-bleaching mills were treated with acetic anhydride in the presence of triethylamine. The acetylated derivatives were removed from the matrix by supercritical fluid extraction (SEE) using carbon dioxide. The best overall recovery for the phenolics was obtained at 110°C and 37 MPa pressure. Two SEE steps had to be carried out on the same sample for quantitative recovery of the phenolics in weathered sediments. The SEE unit was coupled downstream with a GC for end analysis . Off-line SEE followed by capillary GC was applied in the determination of phenol in polymeric matrices . The sonication method recommended by EPA for extraction of pollutants from soil is inferior to both MAP and SEE techniques in the case of phenol, o-cresol, m-cresol and p-cresol spiked on soil containing various proportions of activated charcoal. MAP afforded the highest recoveries (>80%), except for o-cresol in a soil containing more than 5% of activated carbon. The SEE method was inefficient for the four phenols tested however, in situ derivatization of the analytes significantly improved the performance . 

A study was carried out for LEE by the Soxhlet method and microwave-assisted extraction for the determination of the priority phenols in soil samples. Recoveries varied from 67 to 97% with RSD between 8 and 14% for LEE, and >70% for the MAP, except for nitrophenols that underwent degradation when the latter method was applied. LOD was from 20 ngg for 2,4-dimethylphenol to 100 ngg for pentachlorophenol. The best detection method for EC was atmospheric pressnre chemical ionization MS (APCI-MS). The most abnndant ions obtained by this detection method were [M — H] for the lowly chlorinated phenols and [M — H — HCl] for tri-, tetra- and pentachlorophenols . 

Other types of hypercrosslinked sorbents, namely commercial Lewatit EP63, laboratory samples obtained by post-crosslinking styrene-DVB copolymer with CCI4 [55], by self-crosslinking macroporous copolymer of vinylbenzyl chloride with 20% DVB via Friedel-Crafts reaction [56], or by bridging preliminary chloromethylated macroporous styrene-DVB copolymer [57, 58], are all superior to XAD-2, XAD-4, and activated carbon Ambersorb XE340 with respect to phenol and nitrophenol removal. Material [20%-VBC(F.C.)] retains 2,4-dichlorophenol much stronger than unsubstituted phenol, and, therefore, the presence of phenol in the solution does not impact the retention of the chlorinated phenol. On the contrary, the sorption of phenol from the binary solution depends heavily on the concentration of 2,4-dichlorophenol. 

Chlorinated phenols are commonly used as intermediates for the manufacture of agricultural chemicals and wood preservatives. o-Chlorophenol is obtained as the main product from chlorinating of phenol with NaOCl/HCl it is used to manufacture pentachlorophenol and the insecticide profenofos. 

With electrochemistry The advantages of using ultrasound in conjunction with electrochemistry have already been referred to above (Table 10.6). This combination has been particularly beneficial in the destruction of phenols by electrochemical oxidation. Ultrasound (25 kHz, lO" W m" ) when applied to a solution containing phenol (100 g 1 ) and NaCl (2 g 1 ) achieves better than 80% oxidation to maleic acid [55]. In the absence of ultrasound only 50% decomposition was obtained under the same conditions. In a more recent study Berlan et al. have achieved almost complete sonochemical destruction of phenol in saline solution at pH 6 in 10 min at a current density of 170 A m [56]. The reaction was shown to proceed via intermediate chlorinated phenols. 

A new TLC spray reagent, tetiaalkylbenzidine, was introduced for their detection (48) (Table 2). Chloidane and 14 other OC insecticides were analyzed in water samples by TLC using a hexane-ethyl acetate mobile phase. The detection limit was 1-2 pg/spot obtained with o-tolidine (49) (Table 2). The degradation products of OC insecticides are chlorinated phenol derivatives. A procedure was developed for their determinatitni on silufol (silica gel) plates eluted with hexane-benzene-ethyl acetate (6 4 1) (SO) (Table 2). The results of TLC were further confirmed by mass spectrometry (MS) and GLC. 

Production Mono-, di-, and trichlorophenols with no chlorine in a meta position are obtained by direct chlorination of melted phenol with gaseous chlorine. Tetra- and pentachlorophenol are produced batchwise by the chlorination of less chlorinated phenols in the presence of a catalyst (AlCI, FeCl j). Mono-, di-, and trichlorophenols with chlorine in a meta position cannot be obtained by the chlorination of phenol, but must be prepared by other types of reactions, such as hydrolysis, sulfonation, hydrodechlorination, hydro)qrlation, and alkylation. 

Synthesis. Titanium alkoxy halides are intermediates in the preparation of alkoxides from a titanium tetrahaUde (except the fluoride) and an alcohol or phenol. If TiCl is heated with excess primary alcohol, only two chlorine atoms can be replaced and the product is dialkoxydichlorotitanium alcoholate, (RO)2TiCl2 ROH. The yields are poor, and some alcohols, such as aHyl, ben2yl, and /-butyl alcohols, are converted to chlorides (46). Using excess TiCl at 0°C, the trichloride ROTiCl is obtained nearly quantitatively, even from sec- and / f/-alcohols (47,48). 

Commercially, hydrogen chloride is obtained either as a by-product in the manufacture of salt cake from sodium chloride, or by allowing chlorine produced as a by-product in electrolytic processes to react with hydrogen in the presence of activated charcoal. It is also formed as a byproduct in the manufacture of phenol. 

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