Bromophenol reaction + amines

The mechanism of the orf/to-dibromination of phenol with NBS in the presence of amines is considered as follows. The hydrogen bonding between phenol and N-bromoamine which are generated from the reaction of NBS and amines (ref. 14), is the driving force, and causes the bromination at one o/t/io-position of phenol and regeneration of the amines. A catalytic amount of the amines is enough because of the regeneration of the amines. The repetition of the above process causes one more substitution at the other orf/io-position of 2-bromophenol. In the cases of 2-substituted phenols the orf/io-bromination can occur only once (Scheme 5). 

A method suitable for quantification of the functional class of bis(ethanol)amine antistatics, which lack UV chromophores, consists of reaction with methyl orange [53]. Atmer 163 (alkyl-diethanol amine) has been determined as a yellow complex at 415 nm after interaction with a bromophenol/cresole mixture [64]. Hilton [65] coupled extracted phenolic antioxidants with diazotised p-nitroaniline in strongly acidic medium and carried out identification on the basis of the visible absorption spectrum in alkaline solution. The antioxidant Nonox Cl in... 

Colored reagents to follow the appearance or the disappearance of a functional group have been widely used to monitor reactions in classical organic chemistry, particularly in TLC analysis. This technique has been successfully adapted to SPS for example, ninhydrin (118), bromophenol blue (119), nitrophenyl isothiocyanate-O-trityl (120), picric acid (121), and malachite green isothiocyanate (122) have all been used to show the presence or the absence of free resin-bound amines. The presence of free resin-bound thiol groups can also be detected (123). 

Bromophenol Blue is a dibasic acid, and reacts quantitatively with one mole of aliphatic amine to give species IV, which is the acidic species referred to in Table 20. The reaction referred to in Table 18 is the formation of the second complex, V, viz. 

Kinetics of a quite different type are observed for the reactions of Bromophenol Blue with aromatic amines. Aromatic amines are such weak bases that only the first acidic function of Bromophenol Blue is involved, and the product of the reaction is of type IV. The overall rate of formation of the ion-pair from the acid and the base is found to be many orders of magnitude less than the diffusion-controlled rate, and, for several amines, has a negative enthalpy of activation [97], These data, listed in Table 21, can be interpreted in terms of the rate-limiting step being the intramolecular conversion of the hydrogen-bonded species ROH—B to the ion-pair RO —HB+. Although the reaction consists of the... 

Rate coefficients for the reaction of Bromophenol Blue with aromatic amines at 25 °C in chlorobenzene... 

The formation of the imines and their subsequent reduction was monitored by the disappearance of the starting amine (ninhydrin staining, TLC). Simple quenching with water and drying of the organic solutions with MgS04 constituted the reaction work-up. The condensation of the amines with isothiocyanates and TEA was monitored by TLC (blue bromophenol staining, disappearance of... 

The one-pot synthesis of 2-substituted-3-carboxychromones is readily attained by the reaction of 3-oxo-3-(2,6-di luorophenyl)propanoates and acyl chlorides (13CC5313) and of 3-[2-(methoxymethoxy)phenyl]propio-lates and aldehydes followed by DDQ oxidation of the formed chroma-nones (13T647), via transition metal-free approaches. Palladium(II) -catalyzed cascade carbonylative cyclization of 2-bromophenols and terminal alkenes gives chromones 44 in moderate to good yields. Variation on the amine used in the catalytic system led to aurones 45 as major products (Scheme 74) (13TL1802). 

The thermodynamic and analytical aspects of acid-base reactions in aprotic solvents are surveyed in reviews by Davis [1, 2]. The correlation of acid-base strength in water and aprotic solvents is of major importance. Early kinetic work by Bell and co-workers on the acid catalysis of (i) the ethyldiazoacetate-phenol interaction [3] (ii) the rearrangement of N-bromoacetanilide [4] and (iii) the inversion of /-menthone [5] established an order of acid strengths in aprotic media and the importance of intra-molecular hydrogen bonds e.g in picric acid). A thermodynamic method using reference acids and bases is more direct, and Bell and Bayles [6] employed the indicator acid Bromophenol Blue to obtain a basicity order for weak amine bases. Kinetic measurements on these systems have recently been made, and are considered in detail in Section 7. 

Arynes combine with all kinds of polar compounds such as lithium halide, alcohols, primary, secondary or tertiary amines, phosphines, and boranes. Of practical, even technical, importance are their reactions with metal hydroxides and alkoxides. The conversion of chlorobenzene by sodium hydroxide at 350 °C into sodium phenolate, an industrial process, obeys the elimination/addition mechanism. Again arynes can be postulated as plausible intermediates. Regardless of which isomer of bromophenol or of bromophenyl benzenesulfonate is heated with sodium hydroxide, resorcinol is always isolated as the main or sole product after neutralization. 

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