Mononuclear reactions

Even if AE > 0, the question of the probability of a radioactive decay process is still open. It can only be answered if the energy barrier is known. The energetics of radioactive decay are plotted schematically in Fig. 4.1. The energies of the mother nuclide and the products of the mononuclear reaction differ by AE. But the nuclide A has to surmount an energy barrier with the threshold energy Es. The nuclide may occupy discrete energy levels above ground level. However, only if its excitation... 

Whereas the probability of a mononuclear reaction (i.e. for radioactive transmutation) is given by the decay constant 2, two probabilities are decisive in the compound nucleus model the probability that the projectile x will react with the nuclide A (the first step of reaction (8.5)) and the probability that the nuclide B is produced (the second step of reaction (8.5)). 

Yields of nuclear reactions can also be calculated, if binuclear reactions and mononuclear reactions (decay) occur simultaneously, A simple case is the decay of the nuclide produced by a binuclear reaction ... 

Mononuclear reactions. Adsorption producing mononuclear surface complexes, accompanied by deprotonation or hydrolysis of AlOH and/or Co(II), is represented by the generic reaction ... 

This is a mononuclear reaction. In nuclear science, however, binuclear reactions are generally understood by the term nuclear reaction. They are described by the general... 

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high labihty, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds... 

Benzisothiazole is lithiated at the 3-position, which corresponds to the 5-position in the mononuclear series (75JHC877). 4-Methylisothiazole forms the 5-lithio derivative, but the presence of by-products produced in subsequent reactions suggests the possibility of lithi-ation at the 3-position also (72AHC(14)l). 3-Substituted 1,2-benzisothiazoles suffer attack at sulfur and cleavage of the N—S bond (72AHC(14)43, 73SST(2)556). 

Isothiazole itself is best prepared by the reaction between propynal, ammonia and sodium thiosulfate (see Section 4.17.9.3). A wide range of substituted mononuclear isothiazoles can be obtained by oxidative cyclization of y-iminothiols and related compounds (see Section 4.17.9.1.1). Substituents at the 3-position need to be in place before cyclization, but 4-substituents are readily introduced by electrophilic reagents (see Section 4.17.6.3), and 5-substituents via lithiation (see Section 4.17.6.4). 

Pt(PPh3)4] reaction also occurs with elimination of PPh3 but the product is the yellow, planar, mononuclear complex lPi( j -02)(PPh3)2] (Fig. 14.6b).t >... 

Reactions of the metallocene derivatives of molybdenum with pyrazole lead to the mononuclear complexes of the type 22. Structure 22 shows that it cannot be used as a ligand for the preparation of dinuclear complexes owing to geometric constraints [80JOM( 197)291 83JOM(253)53]. In acetone, an unusual complex 23 is formed [83JOM(253)53]. The bidentate ligand is the product of the reaction of pyrazole and acetone. 

Sodium pyrazolate and 3,5-dimethylpyrazolate, [( " -cod)Rh(/A-Cl)]2, carbon monoxide, 3-(diphenylphosphino)benzoic acid, or (2-formylphenyl)diphenyl-phosphine give rise to complexes 120 (R = H, Me) and 121 (R = H, Me) [94JOM(469)213]. However, 2-(diphenylphosphino)benzoic acid (the carboxyl group in the ortho position) leads to formation of the mononuclear complexes 122. The products appear to be catalysts for hydroformylation reactions [93MI2]. 

Diphenylimidazole with palladium acetate forms the cyclometallated complex 80 (X = OAc) (97AOC491). The acetate group is replaced by chloride or bromide when 80 (X = OAc) reacts with sodium chloride or lithium bromide, respectively, to give 80 (X = C1, Br). Bromide with diethyl sulfide forms the mononuclear complex 81. Similar reactions are known for 1 -acetyl-2-phenylimidazole (96JOM(522)97). 1,5-Bis(A -methylimidazol-2-yl)pen-tane with palladium(II) acetate gives the cyclometallated complex 82 (OOJOM (607)194). 

Methylphenyl)benzothiazole (80IC762) and 2-benzylbenzothiazole (95ICA(239)125) can be cyclopalladated. In the latter case, cylopalladation occurs upon reaction with palladium(II) acetate and gives the product 80. With lithium chloride, sodium bromide, or sodium iodide, a series of three products of substitution of the acetate group 81 (X = C1, Br, I) results. Pyridine, 2- and 3-methylpyridine, 2,6- and 3,5-dimethylpyridine cause the transformation of the chelate complexes 81 (X = C1, Br, I) and formation of the mononuclear products 82 (R = z= R" = = R = H, X = Cl, Br, I ... 

Toluene (methylbenzene) is similar to benzene as a mononuclear aromatic, but it is more active due to presence of tbe electron-donating metbyl group. However, toluene is much less useful than benzene because it produces more polysubstituted products. Most of tbe toluene extracted for cbemical use is converted to benzene via dealkylation or disproportionation. Tbe rest is used to produce a limited number of petro-cbemicals. Tbe main reactions related to tbe cbemical use of toluene (other than conversion to benzene) are the oxidation of the methyl substituent and the hydrogenation of the phenyl group. Electrophilic substitution is limited to the nitration of toluene for producing mono-nitrotoluene and dinitrotoluenes. These compounds are important synthetic intermediates. 

---