Adducts structures

Probing DNA Adduct Structures with 13C-Labeled Methides... 

All these extended spoke adducts structurally resemble Z -shaped X82-polyhalides (X = I, Br) in which two asymmetric X3 trihalides are bridged by an X2 molecule.15 This further supports the above-mentioned similarity in the chemical nature of asymmetric X3 trihalides and linear E-X-Y systems in C.-T. adducts. 

It has recently been pointed out that further information may be obtained regarding PBN spin-adduct structure by means of ENDOR spectroscopy whereby small long-range hyperfine splittings may be resolved (Kotake et al., 1977). 

Potential conversion of the N1 adduct to its N derivative was made possible through a Dlmroth rearrangement, although the efficiency of this process is highly dependent on reaction conditions and adduct structure (Scheme 2). (From Veldhuyzen et ah, 2001)... 

This reaction has been written in a generalized manner the Rj substituents are H or Me, depending on the nucleophile under consideration. Although no details of the adduct structures can be obtained through the kinetic measurements, a deprotonation of the binding N-atom of the nucleophile is assumed. As a second key hypothesis, if another H-atom is bound to the central N (R3 = H) in Eq. (9), it should be reactive toward OH-. Further proton transfer and electronic... 

The ANRORC mechanism is also supported by the isolation of a small amount of the open-chain 3-amino-l-phenylallylidene cyanamide (36) (Scheme 2) from the products of the reaction of 2-bromo-4-phenyl-pyrimidine as formed from an adduct structurally related to 35a.100... 

Name S 8 Reagent (X—Y) Structure Name Adduct Structure... 

Based on chemical kinetic evidence, it is now clear that OH reactions with CS2, CH SCH and CH3SH proceed primarily via formation of relatively short lived addition complexes. However, it should be emphasized that none of these short lived complexes have been observed, and no structural information, either experimental or theoretical, is available for any of them. In the case of the OH...CS2 adduct, for example, it is not obvious whether OH binds to the carbon atom or to a sulfur atom. A detailed understanding of the reactivify trends discussed above will not be forthcoming until adduct structures are elucidated. 

Other imine-like adduct structures reported include the phosphinimine of Entry 30149 and the coordinated nitrile in the vanadocene complex shown in Entry 31.150 The tellurium diimide dimer (Entry 32) also coordinates one equivalent of B(C6F5)3 and this adduct has been crystallographically characterized.151 The structure features weak... 

NMR thus, 19F splittings due to UB—19F coupling, and their disappearance at lower temperatures due to quadrupole relaxation of UB, give a measure of the electric field gradient about boron and, hence, of the adduct structure (27, 28). 

Similar to the case of C60,105,223 some exploratory work on the regio-chemistry of single and double osmylation of C70 was done by Hawkins and co-workers.224 A major and a minor mono-adduct were assigned the Cs-symmetric C(l)-C(2)- and C(5)-C(6)-adduct structures (cf. Figure 1.6), respectively. After re-submission of the mono-adducts to osmylation, a total of nine compounds was reported, but no individual structural assignments were made.224... 

Figure 1.32. Confidently assigned C76 adduct structures Two constitutional isomers of Diels-Alder adducts (top) and a diastereoisomeric pair of Bingel adducts (bottom). The latter have enantiomeric C76 cores and could be configurationally assigned by comparison of their CD spectra to those of the optical antipodes of the parent fullerene.

From the [8 + 2] cycloaddition of 8-methoxyheptafulvene to C70, the same group isolated a chiral isomer for which they proposed a C(l)-C(2) adduct structure (C7o-analogue of ( )-230 cf. Scheme 1.22).246 The same regioiso-mer was identified by Taylor and co-workers as the main product of the [4 + 2] cycloaddition of pentamethyl cyclopentadiene to C70.447 A C -symmetric Diels-Alder adduct is, finally, expected from the reaction of C70 with 2-[(ferrocenyl)methylene]-3-methylenequinuclidine.448... 

Thebaine Diels-Alder Adducts—Structure-Activity Relationships... 

Fulleropyrrolidines constitute an important family of Ceo derivatives that have the advantage over the methanofullerene systems in that they lead to stable reduced species, allowing the development of fullerene-based redox molecular switches. In order to promote mesomorphism in such a mono-adduct structure, Deschenairx et al. decided to modify the Ceo derivative by the use... 

The reaction mechanism reported in the reaction of OH with benzaldehydes is shown in Scheme 2. The OH radical attacks the ring [reaction (2)] and the -CHO group [reaction (4)]. The attack of OH on the ortho-position of benzaldehyde was considered negligible because of the lack of formation of salicylaldehyde under steady-state conditions. The two hydroxycyclohexadienyl radicals (structures 2 and 3) were oxidized to the corresponding phenols in the presence of an oxidant [reaction (3)], while the ipso OH adduct (structure 4) was not. 

Since the measured yields of the phenolic products corresponded to 30% OH yield, the ipso adduct formation is limited to 10% OH yield. Since the combined G value of m- and -hydroxybenzaldehydes in NjO-saturated solutions in the presence of IrCl is 1.7, only 30% OH seems to add to the ring. The reason for low phenolic yields in the case of benzaldehyde is the possibility of another reaction channel leading to the formation of the exocyclic OH adduct (structure 5) from the addition of OH to the carbonyl group of benzaldehyde [reaction (4)]. 

Radiation chemical oxidation of benzaldehyde to benzoic acid is interpreted in terms of the disproportionation of the exocyclic OH adduct (structure 5) to give benzoic acid [reaction (5)], which can account for the complete consumption of OH. Dimerization of this adduct seems to be a minor process. 

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