Question

Please fill out the following table, indicating the category of reaction (Swi or Sm2) that will occur in each set of alkyl halides and nucleophiles. If no reaction occurs, write 'NR." Alkyl Halide Strong Nucleophile Weak Nucleophile SN2 SNZ SN2 SNI SNL SNU SNI SNI Methyl 10 2° 3° When determining which mechanism (Sw1 or S2) occurs, the following process is helpful: 1) Determine the substitution (methyl, 1º, 2º, or 3º) of the alkyl halide 2) Determine the strength of the nucleophile Alkyl Halide Substitution: Methyl 1° 2° 3° Nucleophile Strength: Strong Weak Mechanism Type: Sw1 S2 Predict all substitution products including stereochemistry. Additionally, provide the mechanism of the reaction. CH3 NaN, Br 2 Alkyl Halide Substitution: Methyl 1° 3° Nucleophile Strength: Strong Weak Mechanism Type: Sw1 S2 Predict all substitution products including stereochemistry. Additionally, provide the mechanism of the reaction. CH3 OTS HO CH3

Answer 1

CH3 CH3 1. NaN3 Azide ion is a very strong nucleophile. Hence it does a SN2 type of substitution reaction on the given alkyl halide, attacks the carbon bearing Br from backside due to which the leaving group Br leaves. The stereochemistry also changes. Since the attack happens from backside, inversion in congiguration occurs and now the CH3 and N3 groups are cis with respect to each other. OTS HO 2. Formation of carbocation Slow step Attack of the weak nucleophile on the carbocation. Here the nucleophile is weak. Hence it does a SN1 type of reaction. It happens in two steps: firstly a carbocation forms; then the nucleophile attacks on the carbocation. Here the nucleophile can attack the carbocation from both above and below the planes and hence we see a 50:50 mixture of the two products. A racemic mixture is obtained.