66693-92-3Relevant articles and documents
Mechanism of Reactions of N-(Methoxymethyl)-N,N-dimethylanilinium Ions with Nucleophilic Reagents
Knier, Barry L.,Jencks, William P.
, p. 6789 - 6798 (1980)
The prediction that the oxocarbonium ion derived from formaldehyde should have a "lifetime" of ca. 10-15 s that gives rise to an enforced preassociation or concerted reaction mechanism has been tested by examining the reactions of N-(methoxymethyl)-N,N-dimethylanilinium ions in water in the presence of added nucleophilic reagents.These compounds undergo well-behaved second-order reactions with nucleophiles and give the amount of substitution product that is expected from the rate increase in the presence of nucleophile.Structure-reactivity correlations exhibit behavior intermediate between that expected for SN2 (Swain-Scott) and carbonium ion (N+) reactions.The small values of s = 0.3 and βnuc = 0.14 and large values of β1g = -0.7 to -0.9 indicate a transition state that can be described either as an open transition state for SN2 displacement or as an oxocarbonium ion that is stabilized by weak interactions with the entering and leaving groups.Secondary α-deuterium isotope effects for the second-order reactions range from (kH/kD)/D = 0.99 for fluoride ion to 1.18 for iodide ion.Solvolysis and the second-order reaction with n-propylamine exhibit values of ΔS(ex) = -1.2 and -2.1 cal K-1 mol-1, respectively, and display similar changes in rate in mixed water-alcohol solvents.It is suggested that the lifetime of the carbonium ion species in the presence of nucleophiles is so short that the reaction mechanism must be concerted.
