Phenanthrene, halogenation

The fusion of a second aromatic ring results in subtle changes in reactivity. Halogenation of naphtho[l,2-c]-l,2,5-thiadiazole (42) occurs either by 4,5-addition of chlorine (43a) or by 5,6-substitution (44) by bromine. This heterocyclic analog of phenanthrene behaves like phenanthrene in that it gave the 4,5-addition product (43b) when treated with Br2 in glacial acetic acid (Scheme... 

The FEED technology effectively treats hydrocarbons (e.g., gasoline and fuel oils), non-halogenated aliphatic hydrocarbons, and polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene, and benzo(a)pyrene. 

Anthracene is even more reactive than phenanthrene and has a greater tendency to add at the 9,10 positions than to substitute. However, the addition products of nitration and halogenation readily undergo elimination to form the 9-substitution products ... 

Data for the substitution reactions of fluorene, Table 8, are more restricted. In the chlorination of fluorene (Beaven et al., 1962) merely 69% of the chlorine is consumed with the formation of 4-chlorofluorene. Appreciable quantities of the halogen are diverted to addition products as with biphenyl and phenanthrene. 

Carbon-halogen bond cleavage in aryl halides is believed to involve initial excitation into an upper singlet state that is stable with respect to cleavage, followed by intersystem crossing to an upper triplet state that is either dissociative itself or can cross to an upper dissociative (a, a ) triplet [65-67]. The two-color approach has been used to demonstrate directly that excitation to an upper triplet state results in carbon-halogen cleavage. For example, in 2-bromonaphthalene (81) and 9-bromo-phenanthrene (82) [68], promotion of Tj to an upper triplet by dye laser excitation... 

For the preparation of chlorides or bromides, the diazonium salt is decomposed with a solution of cuprous chloride or bromide in the corresponding halogen acid (Sandmeyer reaction). It is possible to prepare the aryl bromide from the diazonium chloride or sulfate. A variation Involves the use of copper powder and a mineral acid for the decomposition step (Gattermann reaction). Both procedures are illustrated by the syntheses of the isomeric bromotoluenes and chlorotoluenes. The usual conditions of the Sandmeyer reaction fail in the preparation of the chloro- and bromo-phenanthrenes. However, these compounds can be successfully obtained by the interaction of the diazonium compound with mercuric and potassium halides (Schwechten procedure). Another procedure for formation of aryl bromides involves treatment of the amine hydrobromide with nitrogen trioxide in the presence of excess 40% hydro-bromic acid. The Intermediate diazonium perbromide is then decomposed by heat. ... 

This area of aromatic photochemistry continues to expand and is now attracting very wide interest, ptossibly because of the successful application of the various processes as synthetic steps for both naturally occurring compounds and those of more academic interest. Research continues into the established areas of cyclizations involving stilbene-phenanthrene systems, enamides, ethenyl-aryl ethers, and closure by loss of halogen acid, but other processes of different types are now being reported which have interesting synthetic potential. The topic of photocyclization of aromatic compounds has also been the... 

Although a stable dibromide cannot be isolated for a similar study of the bromination of benzene, the kinetics of the iodine catalyzed bromina-tion of benzene is identical with that of phenanthrene.26 Consequently it is very probable that the mechanism of the halogenation of benzene is the same as that proposed for phenanthrene. The kinetics of chlorination,27 bromination,28 and iodination by iodine chloride29 are also in agreement with this interpretation. The halogenation of phenols, however, appears to be a different, more complex process. 0... 

With these generalizations the Ea of other compounds can be estimated and used to optimize the CURES-EC results. The Ea of phenanthraldehyde should be about 0.6 eV greater than that for phenanthrene or 0.3 + 0.6 = 0.9 eV. The experimental value is 0.9 eV. The values for the chloroanthracenes should be approximately 0.2 eV greater than that of anthracene or 0.2 + 0.68 = 0.88 eV. The experimental values are 0.8 to 0.9 eV. Multiple substitutions for the NO2 and CN groups in benzene level off with three groups. The substitution of halogens in benzoquinone level off with three substitutions. 

The coupling has to be performed in this way because McMurry coupling of dibromodiacylbiphenyl 83 proceeds with dehalogenation. Halogenation of the resulting 9,10-dialkyl(diaryl)phenanthrenes 84 occurs at the 3 and 6 positions so providing a route to the poly(3,6-phenanthrylene)s 85 (Scheme 37). 

Addition Reactions.- The photoelectron transfer process of the iminium salt (38) with the 3-butenoate anion results in the formation of the allylated product (39). The reaction involves decarboxylation of the 3-butenoate followed by a radical coupling reaction. The photoaddition of halogenated alkenes to the tetraraza phenanthrene (40) yields products (41) of (2+2)-addition. The Eu(III)/Eu(II) photoredox system has been studied with regards to its reactivity toweu ds a-methylstyrene. Irradiation of the system at > 280 nm in methanol yielded the products (42) and(43). ... 

Trimethyl phosphate containing phosphorus pentoxide is a useful medium for the halogenation of aromatic substances which are sensitive to hydrogen halides, and also for the nitration of phenanthrene. ... 

To date, the organic substances studied via ONP have typically been planar, aromatic molecules in pure or mixed crystalline form. While ONP was first demonstrated in pure anthracene, the most commonly-studied systems for ONP (and related OEP) experiments over the years have been fluorene doped with acridine," " phenanthrene, ° phenazine, ° and anthracene," ° as well as naphthalene and p-terphenyl doped with pentacene. ° ° Other investigations of ONP have included studies of anthracene doped withphenazine, tetracyanobenzene," and tetracene, as well as acridine, ° dibromodiphenylether with benzophenone" and dichlorobenzophenone, and various halogenated benzenes. ... 

Compounds of the type R2AIX (X = H, halogen, OR, SR, NR2) are usually strongly associated, the bond between two aluminum atoms being formed only by the substituents. The degree of association of such compounds depends on the nature of the substituents on the aluminum, and steric factors often play an important part. Dialkyl alanes, R2A1H, in benzene solution are trimeric, irrespective of the alkyl groups bonded to aluminum 103, 247). Some, such as di-l-alkyl aluminum hydrides, are also trimeric in phenanthrene at 100°C (307) ... 

The electrical conductivity of molten sulphur at temperatures up to 200 C has been studied on samples which were specially purified, as well as doped with impurities (paraffin, phenanthrene, benzidine, bromine, and iodine). The current flow below 160 C results from electrophoretically migrating impurities and, by interaction with the impurities, ionized molecules, whereas at higher temperatures conduction is caused by electrons. At the minimum of viscosity of the molten sulphur (154.5 °C) the conductivity shows a maximum, which is shifted by impurities (especially halogens) as much as 10 °C towards lower temperatures, llie effect on the mechanical properties of sulphur by the presence of has been studied. The preparation (3 methods), identification, and testing of are reported. Specimens with an content of more than 16% may be prepared by pouring hot sulphur into cold CSg. An analysis of the results of the study indicates that acts as a typical low-modulus material,... 

Both phenanthrene and anthracene have a tendency to undergo addition reactions under the conditions involved in certain electrophilic substitutions. Halogenation and nitration may proceed in part via addition intermediates ... 

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