Relative Rates of Nucleophilic Substitution Reactions Lab Report - 1

Relative Rates of Nucleophilic Substitution Reactions - Lab Report Example In SN2 mechanisms, primary alkyl halides reacted faster than tertiary ones while in SN1 mechanism the tertiary alkyl halides reacted faster than primary ones. It was concluded that aprotic, polar solvents favoured SN2 reactions while SN1 reactions were favoured by protic, polar solvents. Nucleophilic substitution reactions occur by two major pathways namely SN1 and the SN2 reactions (McMurry 228). In all nucleophilic substitution reactions, the nucleophile (Nu:-) reacts with the substrate (R-X) and substitutes it for a leaving group (X:-) yielding the product R-Nu. For a neutral nucleophile (Nu:), the product is positively charged for charge conservation while for a negatively charged nucleophile (Nu:-), the product is neutral (McMurry 228). In SN2, which stands for substitution nucleophilic bimolecular, the alkyl halide and the nucleophile are involved at the transition state (Carey 306). Bond formation between carbon and the nucleophile aids in cleavage of the bond between carbon and the leaving group. In the changeover position, the carbon atom is partially bonded to the leaving group and the incoming nucleophile (Carey 307). Since the nucleophile attacks the substrate from the side that is opposite the bond to the leaving group, the mechanism leads to the inversion of configuration in the resultant product. Different rates are observed when methyl, primary, secondary and tertiary alkyl halides undergo nucleophilic substitution in SN2 (Carey 310). The rate is faster in methyl halides than in tertiary halides due to steric hindrance offered to the nucleophilic attack by the tertiary halides. In most SN2 reactions, the leaving group is expelled with a negative charge. Therefore, the best leaving groups are those that produce the most stables anions (McMurry 233). Among the halides, I- ion is the most reactive while F- ion is the least reactive. Most aprotic polar solvents cause the solvation of the metal counterion that is