Hi I need help calrifying somethibg here It says it is easier to conduct an SN2
ID: 1065141 • Letter: H
Question
Hi I need help calrifying somethibg here It says it is easier to conduct an SN2 reaction when the halides is less electronegative. That doesn't make sense tome because I reacall that the more electronegative the halide in the alkyl halide the more positive the carbocation is and thus it becomes a better electrophile, isn't that applicable in this situation? Where your trip takes off. GRBITZ Constraints on Enolate Alkylation Fr SN2 reaction Leaving group X can be chloride, bromide, iodide, or tosylate An Vis Mc should be allylic or benzylic On Secondary halides react poorly, and tertiary dnn halides don't react at all because of In competing elimination Gr Ch -X: Tosylate -I Br CI R-X COM R-: Allylic Benzylic H3C- RCH2 Err Enh CHE2202, Chapter 22 Wri Learn, 31 slide Player 31152 AdvertisementExplanation / Answer
The slide talks about the role of substrate in SN2 reactions in determining the rate of the reaction. This is because the nucleophile attacks from the back of the substrate, thus breaking the carbon-leaving group(Tosylate>I>Br>Cl) bond and forming the carbon-nucleophile bond. Therefore, to maximise the rate of the SN2 reaction, the back of the substrate must be as unhindered as possible. Overall, this means that methyl and primary substrates react the fastest, followed by secondary substrates. Tertiary substrates do not participate in SN2 reactions, because of steric hindrance. Structures that can form highly stable cations by simple loss of the leaving group, for example, as a resonance-stabilized carbocation, are especially likely to react via an SN1 pathway in competition with SN2.
Your statement is in favour of the postulates. If a more electronegative group is attached to the alkyl group, the more positive the carbocation. So the order of bond strength between the leaving groups(F>Cl >Br >I> Tosylate).The better leaving group is the one with least electronegativity