Cationic derivatives

Comparison of the rate of nitration of the base with that of a necessarily cationic derivative. 

The electrophile in a Friedel-Crafts acylation reaction is an acyl cation (also referred to as an acylium ion) Acyl cations are stabilized by resonance The acyl cation derived from propanoyl chloride is represented by the two resonance forms... 

Nitrosation (Section 22 15) Nitrosation of amines occurs when sodium nitrite is added to a solution containing an amine and an acid Primary amines y e d alkyl diazonium salts Alkyl diazonium salts are very unstable and yield carbo cation derived products Aryl diazonium salts are exceedingly useful synthetic in termediates Their reactions are de scribed in Table 22 7... 

Polyatomic Cations. Polyatomic cations derived by addition of more protons than required to give a neutral unit to polyatomic anions are named by adding the ending -onium to the root of the name of the anion element for example, PH4, phosphonium ion HjU, iodonium ion H3O+, oxonium ion CH3OHJ, methyl oxonium ion. 

Given stringent requirements for effective sensitizers and the desire to use wavelengths further to the red for therapeutic appHcations, definition of newer sensitizers has been a principal area of research since about 1987. Expanded theoretical and experimental understanding of photophysics has been a key element in identifying new classes of potential sensitizers (93—98). Research has focused on cationic derivatives of Nile Blue (93), metaHo-phthalocyanines (94), naphthalocyanines (95), chlorin-type compounds (96), expanded ring porphyrinoids (97), as well as porphyrins other than hematoporphyrin and its derivatives (98). This work has also been reviewed (10,91). Instmmentation for photodynamic therapy has been reviewed (99). 

It is of interest to compare the stability of the protonated forms of benzo[u], benzo[Z>] and benzo[c] fused pyrroles, i.e. the cations derived from indolizines, indoles and isoindoles. Indolizine gives a stable pyridinium ion and does not polymerize in the presence of acid. 

Alkylthio groups are replaced in nucleophilic substitutions. Such reactions are easy in cationic derivatives for example, in the 1,2-dithiolylium series (539), substituted cydopen-tadienyl ion gives fulvene derivatives (540) (66AHC(7)39). 2-Methylthio groups in... 

The Hiickel rule predicts aromaticity for the six-7c-electron cation derived from cycloheptatriene by hydride abstraction and antiaromaticity for the planar eight-rc-electron anion that would be formed by deprotonation. The cation is indeed very stable, with a P Cr+ of -1-4.7. ° Salts containing the cation can be isolated as a product of a variety of preparative procedures. On the other hand, the pK of cycloheptatriene has been estimated at 36. ° This value is similar to those of normal 1,4-dienes and does not indicate strong destabilization. Thus, the seven-membered eight-rc-electron anion is probably nonplanar. This would be similar to the situation in the nonplanar eight-rc-electron hydrocarbon, cyclooctatetraene. 

The orbital coefficients for the MO of energy a for the phenalenyl system described in Fig. 9.7 are as shown below. Predict the general appearance of the NMR spectra of the anion and cation derived from phenalene. 

Radical cations can be derived from aromatic hydrocarbons or alkenes by one-electron oxidation. Antimony trichloride and pentachloride are among the chemical oxidants that have been used. Photodissociation or y-radiation can generate radical cations from aromatic hydrocarbons. Most radical cations derived from hydrocarbons have limited stability, but EPR spectral parameters have permitted structural characterization. The radical cations can be generated electrochemically, and some oxidation potentials are included in Table 12.1. The potentials correlate with the HOMO levels of the hydrocarbons. The higher the HOMO, the more easily oxidized is the hydrocarbon. 

All the rearranged products derived from (12) and (15) have been rationalized as arising by proton loss or reaction with fluoride ion of the respective homoallylic C-19 cations. The structures of the cations derived from (15) are represented by structures (20) to (24)." ... 

Julid investigated the behavior of terfuran 22 and bis(thienyl)furan 23 by cyclic voltammetry as well as the EPR spectra of the radical cations derived from these two compounds. Condensation of the diketone 20 with sulfuric acid furnished furan 22 in 18% yield, while reaction of diketone 21 with hydrochloric acid produced 23 in 84% yield.In a related report, Luo prepared oligomeric bis(thienyl)furans via similar methodology. ... 

Searching for donoracceptor-substituted anions as well as related cations derived from cyclopentadiene, the azafulvalene 32 was synthesized by condensation of the potassium salt of the pushpull-substituted cyclopentadiene with 3-methyl-2-methylsulfanyl-benzothiazolium tetrafluoroborate (85AG996) (Scheme 9). 

For the results reported in both Table 7.2-3 and Table 7.2-4, the only reported detail concerning the ionic liquid was that it was [EMIM][C1-A1C13]. No details of the aluminium(III) chloride content were forthcoming. As with most of the work presented in this chapter, data are taken from the patent literature and not from peer reviewed journals, and so many experimental details are not available. This lack of clear reporting complicates issues for the synthetic polymer chemist. Simpler and cheaper chloroaluminate(III) ionic liquids prepared by using cations derived from the reaction between a simple amine and hydrochloric acid (e.g., Me3N-E3Cl and... 

If we say that to classify an ion as acidic or basic in water solution, it must change die pH by more than 0.5 unit in 0.1 M solution, then the cations derived from strong bases ... 

Tricarbonyl[t/M-(ethoxycarbonyl)-l//-azepine]iron(0) (30) with the 2-oxyallyl cation derived from 2,4-dibromo-2,4-dimethylpentan-3-one and nonacarbonyldiiron(O) yields a mixture of adducts which, after oxidative decomplexation with tetrachloro-l,2-benzoquinone (o-chloranil), affords the tetrahydrofuro[2,3-A)azcpine derivative 33 and the 3-substituted 1H-azepine-l-carboxylate 34.227... 

PMe3)2H] + (12) with NaH (Eq. 5) [37]. The conformation for these complexes as deduced from 31P NMR spectroscopic data are depicted above. Interestingly the cationic derivative [Co(Bu2Cp)(PMe3)2Me]+ (13) possesses a molecular plane of symmetry. 

Nevertheless, there is evidence from C NMR spectra that some % participation is present, even in the cation derived from 31 Olah, G.A. Berrier, A.L. Arvanaghi, M. Prakash,... 

Interestingly, the sulfanes H2S are both proton acceptors and donors. In the first case sulfonium ions H3S are formed, in the second case hydrogen polysulfide anions HS are the result. While the latter have never been isolated in salts, several salts with sulfonium cations derived from the sulfanes with n = 1, 2, and 4 have been published. However, none of these salts has been structurally characterized by a diffraction technique. Therefore, the structures of the HsSn cations and HS anions are known from theoretical calculations only. 

In addition it is probable that each absorbance has a shoulder on the short wavelength side of the maximum. Application of Sorenson s data would associate the peaks at 590, 660, 730 and 790 nm with ions derived from pentaenes, hexaenes, heptaenes and octaenes respectively and interconversion of A qq to A660 A,q t0 A730 so on corresPonds to an increase In the length of tne ions by one unit in each case. Wasseiman (41) has also studied polyenic cations derived by protonation oF various polyenes but the reliability of his spectral data has been questioned (40) due to the high reactivity of the species concerned. 

Noteworthy NMR studies involving nuclei other than phosphorus have been carried out for some P-chloro-NHPs where the possible occurrence of spontaneous P-Cl bond dissociation was probed by II NMR titrations and 35C1 NMR [20], and for P-cyclopentadienyl derivatives where measurement of solid-state 13C CP-MAS NMR spectra allowed one to substantiate the preservation of the circumambulatory ring migration of cyclopentadienyl groups in the solid state [47], Several neutral and cationic derivatives have also been studied by 15N NMR [20, 53],... 

The diimine palladium compounds are less active than their nickel analogs, producing highly branched (e.g., 100 branches per 1,000 carbons) PE. However, they may be used for the copolymerization of Q-olefins with polar co-monomers such as methyl acrylate.318,319 Cationic derivatives, such as (121), have been reported to initiate the living polymerization of ethylene at 5°C and 100-400 psi.320 The catalyst is long-lived under these conditions and monodisperse PE (Mw/Mn= 1.05-1.08) may be prepared with a linear increase in Mn vs. time. 

The silicon(IV) phthalocyanine (12) is also effective in the photoinactivation of the parasite Plasmodium falciparum384 and various enveloped viruses in red blood cell concentrates.385-387 Other silicon (and aluminum) phthalocyanines have been evaluated for the photoinactivation of viruses cationic derivatives appear to be most effective.388... 

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