Aminophenols structure

A number of azacrown compounds were reported by Lockhart and coworkers in 1973. In a typical case, 2-aminophenol was heated at reflux with an equivalent of tet-raethylene dichloride for 48 h. A mixture of the monoaza-15-crown-5 (5) and the mono-aza-12-crown-4 (4) shown in Eq. (4.4) were obtained. Structural assignments were based on H-NMR, IR and mass spectral data. 

The formation of enamines from carbonyl compounds and secondary amines usually entails as only questionable structural feature, the possible isomeric position of double bonds in the product. Molecular rearrangements have not presented synthetic limitations. A notable exception is the generation of o-aminophenols on distillation of enamines derived from 2-acylfurans 620,621). 

Therapeutic Function Analgesic, antipyretic Chemical Name N-(4-hydroxyphenyl)acetamlde Common Name Paracetamol, Acetylfl-Aminophenol, APAP Structural Formula ... 

Phenacetin, a substance formerly used in over-the-counter headache remedies, has the formula CloH1 N02. Phenacetin is neutral and does not dissolve in either acid or base. When warmed with aqueous NaOH, phenacetin yields an amine, CgHjjNO, whose lH NMR spectrum is shown. When heated with HI, the amine is cleaved to an aminophenol, C5IT7NO. What is the structure of phenacetin, and what are the structures of the amine and die aminophenol ... 

For many decades intramolecular O-coupling was considered not to take place in the diazotization products of 2-aminophenol and its derivatives (for a contrary opinion see, however, Kazitsyna and Klyueva, 1972). The compounds were assumed to be present as one structure only, which can be represented as a mesomer of a phenoxide diazonium zwitterion 6.63 b and a diazocyclohexadienone 6.63 a (see reviews by Kazitsyna et al., 1966 Meier and Zeller, 1977 Ershov et al., 1981). In IUPAC nomenclature 6.63 is called 1,2-quinone diazide, in Chemical Abstracts 6-diazo-2,4-cyclohexadien-one (see Sec. 1.3). More recently, however, Schulz and Schweig (1979, 1984) were able to identify the intramolecular product of O-coupling, i.e., 1,2,3-benzooxadiazole (6.64) after condensation of 6.63 in vacuo at 15 K in the presence of argon (see Sec. 4.2). 

The properties of the diazotization product of 2-aminothiophenol are completely different from those of 2-aminophenol. In the reaction shown in Scheme 6-44 the diazo-thiophenolate (6.66) is not detected at all. The benzo-l-thia-2,3-diazole (6.67) is the stable product. A comparison of spectral data for diazophenoxide (6.63), benzo-l-oxa-2,3-diazole (6.64), and benzo-l-thia-2,3-diazole (6.67) is given in Section 4.2. The l-thia-2,3-diazole structure was first postulated by Le Fevre et al. (1954) on the basis of infrared spectra. 

Benzoxazine, an heterocycle present as structural subunit in many naturally occurring and synthetic bioactive compounds, was prepared under microwave irradiation from a mixture of 2-aminophenol 218 and an a-bromoester 219 (Scheme 80). The reaction proceeded through an initial base-catalyzed alkylation of the phenoUc OH followed by spontaneous amidation. Yields from 44 to 78% were reported for 17 different benzoxazines 220 [ 141]. 

A tridentate N02 donor set complex was formed from 2-pyridinecarboxaldehyde N-oxide and 2-aminophenol and gave mononuclear and trinuclear compounds. The trinuclear zinc complex was structurally characterized and revealed bridging acetate groups, [ZnLZn(OAc)4ZnL].865... 

Those polyester FBAs containing a benzoxazole group are usually prepared from the appropriate o-aminophenol and carboxylic acid (11.45 Y = OH) or one of its derivatives, as shown in Scheme 11.10. The reaction proceeds via an intermediate amide and it can be advantageous to start from an acid derivative such as the acid chloride (11.45 Y = Cl) or ester (11.45 Y = OEt), which are both more effective acylating agents. The preparation of compound 11.36, shown in Scheme 11.11, illustrates this process, but the optimum conditions for ring closure vary considerably from one structure to another. The article by Gold contains a valuable and detailed summary [4]. 

Substrate and intermediate species adsorb on an electrode surface and orient themselves so that their least hindered sides face the electrode, unless there is another effect such as a polar one. An electrode interface has a layered structure in which a nonuniform electric field (some slope of potential) is generated by polarization of the electrode. An extremely strong electric field of approximately 10 V cm i in the innermost layer might cause a variety of polar effects. For instance, electrochemical one-electron oxidation of o-aminophenol derivatives proceeds adiabatically. On the contrary, the homogeneous reaction is nonadiabatic. This difference in behavior is related to... 

The figure represents the chemical structure for paracetamol, which includes the N-(4-hydroxyphenyl) acetamide, derived from the interaction of p-aminophenol and an aqueous solution of acetic anhydride. The structure has two activating groups that make the benzene ring highly reactive toward electrophilic aromatic substitution. 

Glowiak studied the stability of the four diazophenols (59-62), which he prepared from the diazotization of the corresponding aminophenols. It was noted that (61) and (62) show higher chemical stability than (59) and (60) the latter compounds were postulated to have a quinonoid structure rather than a zwitterionic diazophenol structure. 

There are many fluorescent indicators for detection of [Mg +] [319] and fluori-nated NMR reporters have been proposed. The simplest is fluorocitrate [313], which shows a change in chemical shift upon binding Mg +. However, it is critical that the reporter molecule be used as the + isomer only, which has relatively little toxicity [320], Levy et al. [8,321] developed the o-aminophenol-A/,A/,0-triacetic acid (APTRA) structure both for fluorescent application and by incorporation of fluorine atoms for F NMR, which have been used in the perfused rat heart [322]. 

It is now apparent that nitrenium ions occur in a variety of contexts including the so-called Bamberger rearrangement (i.e., acid-catalyzed isomerization of N-hydroxyaniline 14 to 4-aminophenol 15, Fig. 13.9), and the aforementioned catabolism of arylamines. The earlier workers, however, for the most part did not explicitly consider the possibility of such a species. Heller et al. were the first to present kinetic evidence for such an intermediate. Interestingly, they chose to represent it as the iminocyclohexadienyl cation (16), With the customary ellipsis of allowing a single valency structure to represent mesomeric systems. ... 

Sulfur Bake. The yellow, orange, and brown sulfur dyes belong to this group. The dyes are usually made from aromatic amines, diamines, and their acyl and nuclear alkyl derivatives. These may be used in admixture with nitroanilines and nitrophenols or aminophenols to give the desired shade. The color formed is said to be the result of the formation of the thiazole chromophore, evident in dye structure (1). 

A few other PAEH have been reported. One disclosure concerned PAE containing pendent benzoxazole and benzothiazole units [49]. The activated difluoro benzazole monomers, 2-(2,6-difluorophenyl)benzoxazole or benzothiazole, were prepared from the reaction of 2,6-difluorobenzoyl chloride with 2-aminophenol or 2-aminothiophenol in polyphosphoric acid. By H NMR, the benzazole unit was shown to have a greater electron-withdrawing effect on the 2-phenyl group than on the benzo ring [49]. Only a few polymers were reported. As an example, the polymer of structure 12 had an intrinsic viscosity of 0.45 (NMP at 30 °C) and Tg of 170°C [49],... 

The Michael addition reaction has attracted many researchers as a route to convert high melting BMI building blocks into resins with improved processability as compared with the BMI building blocks. Heat resistant resin compositions have been prepared from para- or meta-aminophenol (52). The idealized structure of such a BMI/m-aminophenol adduct is shown in Fig. 19. 

For example, the molecular formula for 4-aminophenol (1,1) is C(iH7NO. The formula of the fully saturated, acyclic parent structure [C H 2,j+2+vNvO ., where H is the total number of hydrogens and halogens] would therefore be C6H(i2+2+i)NO, i.e. C6H15NO. The difference in the number of hydrogens is therefore 15-7 = 8, so there are 4 DBEs. 

Looking at the structure of 4-aminophenoL we can see that formally it has 3 double bonds, and the ring itself makes up the total of 4 DBEs. 

Note Its structure as 2,6-dinitro-3-amino-isomer was established by Borsche Feske (Ref 3). Prior to this, some investigators considered it as 2, 4-dinitro-3-aminophenol [See Beii i3,(137)]. The correct formula is given in Beil 13,[216]... 

In an early publication, Zelentsov reported the preparation of a complex with subnormal magnetic properties 44 = 0.87 BM) with the SB (101).777 The compound was prepared from dibenzoylmethane and o-aminophenol. The V02+ complex with (102) has also been shown to be involved in antiferromagnetic exchange with J = —139 cm-1. Revenko and Gerbeleu prepared several V02+ complexes of (103) derived from Hsal and thiosemicarbazide which were reported to involve ONS coordination.778 The measured were 1.27, 1.21 and 1.33 BM for R = H, Cl and Br, respectively. The complexes are not anhydrous and a dimeric structure (104) was proposed. 

A proposal made about 70 years ago (13MI11400) to use p-phenylenediamines and p-aminophenols as developers which give dyes with a variety of couplers is the basis of present day practice. Since the original idea was formulated numerous developers and couplers have been synthesized. Many subtle effects within the photographic systems can be achieved as a result of the specific structure of the developers and couplers. 

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