Phenanthrenes protonation

The H-NMR spectra of diazocines 91 (R = Ph, R = R = H) and 93 (R = H) confirm twisted conformations of the eight-membered ring in these compounds. The twist in 93 is evidently so great that protons H4 and Hj, expected to be coplanar and therefore deshielded, do not resonate at the chemical shift expected of normal phenanthrene protons (73JCS(P2)2131). The conformation of diazocine 147 was determined by X-ray diffraction. 

Consider the two structures shown for kekulene, one suggesting inner and outer annulenes, and the other a series of phenanthrene-like units. Indicate properties that you would expect to be associated with each structure. Proton NMR and bond-length data are given. How do they compare with your expectations ... 

Reduction of stilbene [18] or dipheny-lacetylene [214] in DME yields 1,2,3,4-tetraphenylbutane, whereas phenanthrene [214] provides 9,9, 10,10 -tetra-hydro-9.9 -biphenanthrene. Hydrodimerization was also observed with benzalfluo-rene [225]. If DME is replaced by acetonitrile, protonation completely dominates hydrodimerization [18]. In carefully dried ethers, using alkali or alkaline earth metals salts as supporting electrolyte, 1,1-diphenylethylene can be reduced ca-thodicaUy to give stable solutions of 1,1,4,4-tetraphenylbutane dianions [226]. These dianions can be cleaved by flash... 

Aromatic 7c-systems bearing two positive charges can accept one electron to form a delocalised radical-cation, which is isoelectronic with the radical-anion from the corresponding aromatic hydrocarbon. The phenanthrene analogue 4 is one such example [30]. Pyrazine is bis-protonated and reduced in acid solution to the... 

Subsequently, a series of regioisomeric a-phenanthrene-substituted carbocations were generated from their alcohols by ionization with FS03H/S02C1F. Model carboxonium ions were also generated by O-protonation of the isomeric acetyl- and... 

The proton NMR spectrum of 1,10-phenanthroline has been obtained and analyzed by several authors in nonaqueous solvents 04-109 and in water at various pH values.28,110 Examples of studies of the NMR spectra of substituted 1,10-phenanthrolines that have been investigated in some detail are also worthy of mention.47,104,106,11° The NMR spectra of all ten phenanthrolines have been determined in deuterochloroform, and the spectra were interpreted12 (Table IV). The spectra of the 1,7-, 1,10-, and 4,7-isomers have also been compared with that of phenanthrene.111 Shifts in the NMR spectrum of 1,10-phenanthroline induced by a europium shift reagent have been discussed,112 and 13C chemical shifts of free and protonated 1,10-phenanthroline were measured.113... 

The details of protonation of several alkyl-substituted phenanthrenes by superacids have been reported.73 The observed mono- and di-cations are usually in agreement with those predicted by AMI MO calculations. Molecular modelling studies have suggested a multi-step pathway for the sulfonation of toluene widi sulfur trioxide.74 Intermediate 71-complcx. Wheland intermediate and pyrosulfonate species (34) are suggested, the product (p-toluenesulfonic acid) arising from an exothermic reaction between toluene and the acid (35) fonned by a facile prototropic rearrangement of (34). The sulfur trioxide monosulfonation of isopyrene and some derivatives leads usually to sulfonated... 

For benzene, it has not been possible to measure directly the rate constant kv for deprotonation of the benzenonium ion in order to complete the determination of Ka (— kp/kg). However, this has been possible for 1-protonated naphthalene,106 9-protonated phenanthrene,25 9-protonated anthracene, and 2-protonated benzofuran.75 In the case of the naphthalene, Thibblin and Pirinccioglu showed that the naphthalene hydrate is sufficiently reactive to form the naphthalenonium ion in aqueous azide buffers (pH 4-5).106 Formation of this ion leads to competition between loss of a proton and trapping by azide ion to form the 2-azido-l,2-dihydronaphthalene. From the trapping ratio kp is determined as 1.6xlOlos 1 by the usual clock method. 

The hydrates of phenanthrene (13), anthracene, and benzofuran are not sufficiently reactive to form carbocations at the mild pH of azide buffers. However, the cation may be generated by solvolysis of their acetate or chlor-oacetate esters. Trapping of the cation by azide ions then occurs in the normal way.25,75 Moreover, the solvolytically generated cations react in these cases not only through loss of a proton to form the aromatic product but by nucleophilic... 

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