Nucleophilicity gas-phase

Gas-phase nucleophilic displacement reactions, 21, 197 Gas-phase pyrolysis of small-ring hydrocarbons, 4, 147 Gas-phase reactions of organic anions, 24, 1... 

Liotta and Grisdale (1975) have reported on the relative nucleophilicities of anions whose potassium salts were solubilized into acetonitrile by 18-crown-6 [3]. The results (Table 28) show the sequence Nj > OAc- > CN- > F- > Cl-x Br- > I- > SCN-, which is very different from the reactivity scale in water CN- > I- >SCN- > Nj > Br- > Cl- > OAc- > F-. Furthermore, the relative nucleophilicities in acetonitrile vary only by a factor of 30, whereas in water they differ by as much as a factor of 1000. The fact that gas-phase nucleophilicities also span a narrow range led the authors to conclude that anion solvation is much less important in acetonitrile than in water. The values recently reported by Lemmetyinen et al. (1978) for the relative nucleophilicities of anions towards methyl methanesulfonate in benzene show the same sequence as in protic solvents, however. The authors offered no explanation for this peculiar behaviour. 

Figure 2. Proposed double-minimum potential surface for gas-phase nucleophilic...

Gas-phase nucleophilic substitution reactions of Y-benzyl chlorides and X-phenoxide or X-thiophenoxide nucleophiles have been investigated by using the PM3 semiempirical MO method. The structure of the transition state was examined. The values of the gas-phase Hammett constants px and py are much greater than for the solution reactions, but a theoretical cross-interaction constant pxy (ca —0.60 for both phenoxides and thiophenoxides) agrees well with an experimental value of —0.62 for the thiophenoxide reactions in MeOH at 20 °C. Other work by the same group has involved theoretical studies of competitive gas-phase 5 n2 and E2 reactions of NCCH2CH2CI with HO and An ab initio method at the 6-31-l-G level was... 

Model for nucleophilic displacement reactions at carbonyl centres 227 Gas-phase nucleophilic reactions of carbonyl systems involving positive ions 229... 

An early attempt to establish the gas-phase nucleophilicities of H, F, OH- and NH2 towards methyl chloride was carried out by Young et al. 

Gas-phase nucleophilic displacement reactions in aliphatic systems involving a neutral nucleophile and a positively charged substrate represent a much more heterogeneous set of reactions than that of negative ions. As for most... 

Gas-phase nucleophilic reactions of carbonyl systems involving positive ions... 

Gas-phase nucleophilic displacement reactions in aromatic systems have until recently received considerably less attention than those in aliphatic systems. This situation is not unlike reactions in solution where these reactions are less common than displacement at aliphatic centres. It is well known that these reactions occur only when strongly activating groups (e.g. nitro) are present in the ring (Miller, 1968). 

Figure 11.6 Menschutkin reaction of ammonia and chloromelhane. In the gas phase nucleophilic displacement fails to take place, while in water solvation of the anions allows the reaction to proceed...

Theoretical studies have been carried out for the gas-phase nucleophilic ring-opening of 3,4-epimino-, 3,4-epoxy-, and 3,4-epithio-but-l-ene.88 Attack by HCP on a-C, y-C, and <5-C was examined by using VIP2/6-31+G //M P2/6-31+G ab initio molecular orbital methods. 

Directive effects, in aromatic substitution, a quantitative treatment of, 1, 35 Directive effects, in gas-phase radical addition reactions, 16, 51 Discovery of mechanisms of enzyme action 1947-1963, 21, 1 Displacement reactions, gas-phase nucleophilic, 21, 197 Donor/acceptor organizations, 35, 193... 

Gas-phase nucleophilic displacement reactions have been extensively studied both by theory and by experiment. Since an excellent review on gas-phase nucleophilic displacement reactions was published in 1985226, the early achievements in this field are only briefly outlined here to provide some background for the most recent developments. 

Finally, a very peculiar type of gas-phase nucleophilic substitution reaction was recently observed to take place between neutral reactants to form ionic products260. Crossed molecular beams were used to study the dynamics of chemiionization S 2 reaction between an alkyl iodide and an amine (equation 27). 

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