Premium
Theoretical Study on the Halogen–Zinc Exchange Reaction by Using Organozincate Compounds
Author(s) -
Nakamura Shinji,
Liu ChingYuan,
Muranaka Atsuya,
Uchiyama Masanobu
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802393
Subject(s) - chemistry , halogen , reactivity (psychology) , alkyl , ligand (biochemistry) , zinc , zincate , density functional theory , medicinal chemistry , reagent , substrate (aquarium) , activation energy , stereochemistry , reaction mechanism , iodide , computational chemistry , organic chemistry , catalysis , geology , medicine , biochemistry , alternative medicine , receptor , oceanography , pathology
Zincate it! The mechanism of the halogen–zinc exchange reaction with organozincate compounds has been studied by using density functional theory to elucidate the effects of changing the halogen species, the alkyl ligand on zinc, and the substrate nature (see figure).Density functional theory (DFT) calculations have been performed to examine the mechanism of the halogen–zinc exchange reaction of organozincate reagents (Me 2 RZnLi ⋅ OMe 2 ; R=Me, Et, i Pr, and t Bu) with organohalides (RX; R=Me, vinyl, ethynyl, ‐CH(Cl)CH 3 , ‐CH(CH 3 )CHCH 2 ; X=Cl, Br, I). We focused on three areas: 1) the effect of the halogen species, 2) the effect of the alkyl ligand on zinc, 3) the effect of the substrate nature. Fragment‐energy analysis of each reaction was conducted to elucidate the factors determining the activation energy. The nature of the halogen atom affects the interaction (INT) energy but does not affect the deformation (DEF) energy. On the other hand, the type of alkyl ligand influences DEF rather than INT and bulky ligands (including tert ‐butyl and iso ‐propyl groups) decrease the activation energy compared with smaller ligands, such as ethyl and methyl groups. In the reaction with vinyl iodide, a decrease in DEF promoted the reaction, whereas INT was almost unchanged. However, in the case of iodoacetylene, a decrease in INT lowered the activation energy. For allyl iodide derivatives DEF appears to be the determining factor, whereas for gem ‐dihaloalkane derivatives INT is the main determinant of reactivity.