Solvation Effects on Alternative Nucleophilic Substitution Reaction Paths for Chloride/Allyl Chloride and γ-Methylated Congeners

Abstract

An adiabatic connection method, mPW1PW91(0.581)/6-31G(d), was employed in conjunction with the continuum solvation model SM5.42 to study the effects of solvation on the S(N)1, S(N)2, and syn and anti S(N)2' nucleophilic substitution reactions of chloride anion with allyl chloride and its gamma-methylated analogues Z- and E-crotyl chloride and isoprenyl chloride. The impact of equilibrium solvation on the potential energy surfaces of these systems is large and leads to significant changes in both the geometries and the relative energetics of different reaction pathways for different species. The predicted effects of increased solvent dielectric constant are consistent with available experimental data and provide semiquantitative insights into the relative influence of different solvents on particular properties.

Effects of ion-pairing and hydration on the SNAr reaction of the F−with p-chlorobenzonitrile in aprotic solvents

“…Another system where an important solvent effect on the geometry was observed is the S N 2 reaction of the chloride ion with isoprenyl chloride in aqueous solution. 42 In order to obtain an accurate free energy barrier, single point calculations were done at MP2 and MP4 levels using up to the extended 6-311þG(2df,2p) basis set and the results are in Table 1. The free energy barrier for the S N Ar reaction is calculated to be 20.3 and 21.4 kcal mol À1 using the PCM/HF/6-31(þ)G(d) and PCM/B3LYP/6-31(þ)G(d) geometries, respectively.…”

Enantiomerically Enriched Tetrahydropyridine Allyl Chlorides

“…20 Acyclic allyl chlorides generally undergo SN2' substitutions as the carbon with the leaving group can freely rotate about the vicinal olefin, 21 but mechanistic studies with cyclic allyl chlorides suggests SN2 substitutions are generally favoured followed by anti-SN2' and syn-SN2' pathways. 4e-h, 22 Our results (Scheme 5-2) show that the %D saturation at C5 of rac-1-d is usually conserved throughout these substitutions, strongly suggesting SN2 reactions. An exception to this trend is seen with thioether 9-d which shows some D transfer to C3.…”

Influence of a β-OH substituent on SN2 reactions of fluoroethane: Intramolecular hydrogen bonding catalysis or inhibition? A theoretical study

“…However, the isolated nucleophile is stabilized to a much greater extent than the transition state due to its more delocalized charge. The other characteristic of the solvated PES is the disappearance of stable ion-dipole complexes (RC and PC) with increasing solvent dielectric due to a decreased attraction of the reactants [37].…”

“…Since most S N 2 reactions occur in solution, a large number of these studies have been devoted to the solvent effects [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. One of these effects that has been broadly examined is H-bonding via protic solvents that lowers the energy of an anionic nucleophile relative to the transition state, in which the charge is more diffuse, and results in an increase of activation energy [1,2].…”