Solvent effects on the free energies of the reactants and transition states in the Menschutkin reaction of trimethylamine with alkyl halides

1969 ◽  
pp. 1307 ◽  
Author(s):  
M. H. Abraham
Keyword(s):  
Solvent Effects ◽  
Transition States ◽  
Alkyl Halides ◽  
Free Energies

Ambident Heterocyclic Reactivity: Alkylation of 4-Substituted and 2,4-Disubstituted Benzimidazoles

1994 ◽  
Vol 47 (8) ◽  
pp. 1523 ◽  
Author(s):  
MR Haque ◽  
M Rasmussen
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Electrostatic Field ◽  
Transition States ◽  
Alkyl Halides ◽  
Methyl Group ◽  
Site Selectivity ◽  
Leaving Group ◽  
Standard Set ◽  
Specific Association

The N1/N3-alkylation patterns of 4-amino-, 4-methyl- and 4-nitro-benzimidazole anions, and their 2-methyl analogues, with a standard set of primary alkyl halides (in dimethylformamide, 30°) have been determined and compared. The observed regioselectivities are dominated by proximal effects-electrostatic field, non-bonded steric and in some cases specific association (hydrogen bonding)-the interplay of which is critically dependent on the (variable) geometries of the SN2 transition states involved, in particular on the N---C distance of the developing N-alkyl bonds. The presence of a symmetrically placed 2-methyl group produces an enhanced N1/N3 site selectivity, very sensitive to the loose-tight nature of the transition state. Halide leaving group effects on butylation regioselectivities of 2-unsubstituted, 2-ethoxy-, 2-methyl- and 2-chloro-4-methylbenzimidazole anions, whilst small, are consistent with a Bell-Evans-Polanyi analysis of SN2 transition state variations, with the earlier transition states of CH3(CH2)3I leading to reduced regioselectivities.

scholarly journals Kinetic solvent effects in the reduction of alkyl halides by {Sm[N(SiMe3)2]2(THF)2}

2018 ◽  
Vol 857 ◽  
pp. 52-57 ◽  
Author(s):  
Tesia V. Chciuk ◽  
Sandeepan Maity ◽  
Robert A. Flowers
Keyword(s):  
Solvent Effects ◽  
Alkyl Halides
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