In solvolysis reactions

A scale for solvent ionizing power, K+, applicable in solvolysis reactions of cationic substrates, has been developed. For example,... 

Participation of carbon-carbon double bonds in solvolysis reactions is revealed in some cases by isolation of products with new carbon-carbon [Pg.313]

AC is interpreted as the difference in heat capacities between the transition state and the reactants, and it may be a valuable mechanistic tool. Most reported ACp values are for reactions of neutral reactants to products, as in solvolysis reactions of neutral esters or aliphatic halides. " Because of the slight curvature seen in the Arrhenius plots, as exemplified by Fig. 6-2, the interpretation, and even the existence, of AC is a matter of debate. The subject is rather specialized, so we will not explore it deeply, but will outline methods for the estimation of ACp. 

Silyl effects in carbocations which were predicted computationally and have been observed in the gas phase and in solvolysis reactions have been proven by NMR spectroscopic investigation of long-lived silyl-substftuted carbocations in... 

Fluoroalkyl Glycosides (RFn-(CH2)2-n-0-sugar) and Perfluor-oalkylidene Acetals Derived from Sugars The very low nucleophilicity of fluoroalcohols makes it difficult to substitute of a hydroxyl (anomeric or not). ° This is the reason why this type of ether is not very common. Such ethers have only been isolated in very small quantities in solvolysis reactions, or in carben insertions, performed in fluorous alcohols.Preparation of these ethers has been solved by means of the Mitsunobu reaction. This reaction is known to be dependent on the pA a of the acceptor of the glycosyl the acidity of fluorous alcohols allows a much easier deprotonation than with non fluorinated alcohols." ... 

Metal Chelate Compounds as Acid Catalysts in Solvolysis Reactions... 

The S j km is responsible for the deep blue color of ihese solutions (Amax = 610 nm). This ion is also responsible for the color of sulfur dissolved in chloride melts (see below) and in the aluminosilicate known as ultramarine (see Chapter 16). Many nonmetal halides behave as acid halides in solvolysis reactions ... 

Carbocations with trivalent carbon may have carbon with coordination number 2. Acyl ions have already been mentioned the vinyl cations, or car-bynium ions (26), have been detected as intermediates in addition of electrophiles to acetylenes and allenes and in solvolysis reactions with the highly reactive trifluoromethanesulfonate (triflate) leaving group.84 Vinyl cations are expected... 

The effect of a-silyl substitution on the stability of a carbenium ion was qualitatively unclear for a long time. Early solvolytic studies by the groups of liaborn36 and Cartledge37 suggest a destabilizing effect of a-silyl substitution compared with alkyl. The measurement and interpretation of the kinetic a-silicon effect in solvolysis reactions is, however, often complicated by the fact that steric and ground state effects may play an important role and that, in addition, the rates of ionization often involve a contribution from nucleophilic solvent assistance. 

In solvolysis reactions, a silicon at the -position greatly facilitates the heterolysis of a C—X bond, often affording exclusively elimination products (equation 19). Thus, already Sommer, Whitmore and coworkers34,35 described a greatly enhanced reactivity of 60 and 61 in their basic hydrolysis in comparison with the corresponding a- and /-substituted systems. 

The experimental dependency of the /J-silyl effect on 0 in solvolysis reactions is sketched in Figure 764. Obviously, it differs from that anticipated for a k mechanism with rate-determining formation of siliconium ion or from the cosine-squared function expected for the pure hyperconjugative stabilization model. Apparently, the /J-silyl effect is operative in the solvolysis of both the syn- and rmt/ -periplanar conformations. The rate acceleration in the latter might be ascribed to a more favourable geometry for the (T-anchimeric assistance. 

Apeloig, Y. Biton, R. Abu-Freih, A. Importance of electronic geminal interactions in solvolysis reactions. Application to the determination of the a-silyl effect on carbenium ion stability./. Am. Chem. Soc. 1993, 115, 2522-2523. 

Interstrand cross-links are unstable in conditions close to physiological conditions [57]. The bonds between platinum and the N(7) of guanine residues are cleaved spontaneously, with essentially one cleavage reaction per cross-linked duplex in either of both DNA strands (tl/2 for the cleavage reaction is about 29 h). As shown in the reaction scheme (Fig. 2), the cleavage generates monofunctional adducts which can react further to yield interstrand and intrastrand cross-links. The distorted local conformation could allow the formation of adducts which are not usually formed in double-stranded DNA containing a monofunctional adduct. An attractive hypothesis to explain the instability of the interstrand cross-links is that one of the two water molecules, in apical position with respect to the square of the platinum atom, labilises the G-Pt bond in solvolysis reaction. When the local... 

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