Naphthalene diprotonated

Lammertsma412 has also obtained dication 198 by the protonation of hexahydro-pyrene in Magic Acid solution. This is the first example of a p,p -diprotonated naphthalene derivative. Koptyug and co-workers270,413 have studied a,a -diproto-nated hexa- and octamethylnaphthalenes 199 under superacidic conditions. 

Shudo and coworkers have reported that 0,0-diprotonated nitroalkenes (16) behave as novel electrophilic species which can efficiently alkylate aromatics such as benzene, anisole, chlorobenzene, naphthalene, etc. under extremely mild conditions (equation 28). The reaction enables the synthesis of a-arylated ketones (17) which are difficult to synthesize by conventional Friedel-Crafts reactions. 

In these strong acid systems one can often ob rve diprotonation of aromatic compounds. Thus, bimesityl and decamethylbiphenyl in HSO3F—SbFj attach the protons at 3- and 3 -positions while 1,2,3,5,6,7-hexamethyl- and octamethyl-naphthalenes, at the 1- and 5-positions from octamethylnaphthalene two isomeric ions are formed corresponding to cis- and trans-diprotonation ... 

Diprotonation was observed, for instance, for polymethylated derivatives of biphenyl and naphthalene in the HSO3F—SbFj and HF—SbFj systems... 

Hexahydropyrene is shown to be protonated in HSOjF at the p-position of the naphthalene ring diprotonation is achieved in the system HSO3F—SbFj... 

A glimpse on the chemical formulas is sufficient to tell, that the monocation of the pyrazine has the same symmetry as H2O that corresponds to the symmetry group C2v (see Table C.4), while the pyrazine and its diprotonated derivative have the symmetry identical with that of the naphthalene i.e., D2h- Let us focus first on the last case. 

Carbocations can be generated by protonation of unsaturated hydrocarbons such as alkenes and cycloalkenes, cyclopenta-dlenes, benzenes and naphthalenes (eq 4), pyrenes and cyclophanes, unsaturated heterocycles,and their derivatives with carbon-heteroatom multiple bonds, Including carbonyl and nitrile compounds and diazoalkanes (eq 5). Compounds with two sites for protonation may undergo diprotonation to give dicatlons In Magic Acid (eq 6). ... 

In order to accommodate the later kinetic data, 77-complex formation from the diprotonated substrate had to be introduced , despite a previous theoretical demonstration that this was improbable. As the earlier versions of the theory also could not account for the kinetic order of the reaction of hydrazo-naphthalene and of semidine- and diphenyline-forming rearrangements , or for the products and kinetics for compounds with bulky para substituents , and furthermore, led to incorrect general rules for products, there seems little justification for its continued advocacy. The latest version of the theory has been stripped of its quantitative content, and is little more than a statement that the reaction is intramolecular and has some kind of (unspecified) interaction between the different potential fragments, as they readjust their relative positions. 

---