D&C of nuclephilic substitution

D&C of nuclephilic substitution - Marta...

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Marta Gebregziabher Lab 5: Nucleophilic substitution: Preparation of 1-bromobutane, Alkyl Halide classification tests 1. A nucleophile substitution is a reaction in which a partially positive atom, which is referred to as electrophone, is attacked by a nucleophile or an electron rich atom. The reaction produces a leaving group, which will be stable on its own and also produces a new bond. There are two main reactions when it comes to substitution reactions, SN1 and SN2 reactions a. SN1- SN means Nucleophilic substitution and “1” means that the rate determining step is unimolecular. There are two steps for SN1 reactions of which the first step is the rate determining step. During the reaction, the rate depends only on the reactant. Also during the reaction there is the formation of an unstable carbocation. This is facilitated by normal solvents which typically are protic and polar. The polarity stabilizes ionic intermediates and the protic characteristic helps the leaving group solvate. b. SN2-SN means Nucleophilic substitution and the “2” means bimolecular. This is a reaction where the electrophile, which is electron deficient, is attacked by the nucleophile with a lone pair. This reaction only takes place in one step and there for it’s the rate determining step. The most common carbon that the aliphatic carbon and usually a halide atom are attached to it. A leaving group is considered to be good, if it’s a weak base but a strong acid. Also the solvent has to be protic
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This note was uploaded on 12/04/2009 for the course CHE 210 taught by Professor Swinnea during the Spring '08 term at University of Texas.

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D&C of nuclephilic substitution - Marta...

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