88825-18-7Relevant articles and documents
Kinetic Isotope Effects in the Menschutkin-Type Reaction of Benzyl Benezenesulfonates with N,N-Dimethylanilines. Variation in the Transition-State Structure
Ando, Takashi,Tanabe, Hiroshi,Yamataka, Hiroshi
, p. 2084 - 2088 (2007/10/02)
Primary carbon-14 and secondary α-tritium isotope effects were measured for the Menschutkin-type reaction of m-bromobenzyl-methylene-14C X-substituted benzenesulfonates with Y-substituted N,N-dimethylanilines in acetone at 35 deg C (eq 1; Z=m-Br).The large carbon-14 (12k/14k = 1.117-1.151) and small α-tritium (Hk/Tk = 1.026-1.041) isotope effetcs were consistent with the SN2 mechanism of the reaction.A monotonous trend was observed when the carbon isotope effects were plotted against the relative rates for varied Xs and a fixed Y (p-CH3), while a bell shape was observed for varied Xs and a fixed (p-Cl).Comparison of the results with those obtained for the unsubstituted benzyl esters indicated that the substitution on the benzyl moiety with the electron-withdrawing m-Br group made the transition state more product-like.Smaller α-tritium isotope effects for the m-Br series than those for the unsubstituted series verified tighter transition states for the former.The variation in the three-centered SN2 transition states caused by the substituents on the leaving group, the nucleophile as well as the benzyl moiety, is discussed in terms of Thornton's rules and described on a potential energy map.
