Question

mism for the following substitution reactions a mechanism I1. Propose a determine if they are SnI or Sv2. N, DMSO (solvent) H.s SH +TSOH KOCH d. NaOEt e. C/ SH

Answer 1

a) In this reaction, NaN is strong nucleophileand Bromineis good leaving group. Also DMSO is polar aprotic solvent. Therefore, this reaction follows SN2 mechanism. Since this is one step reaction, N3 attacks frombackside to produce product having inversion in stereochemistry 1-azido-3-methylcyclohexane CH 1-bromo-3-methylcyclohexane b) This is also Sv2 reaction mechanism in which H2S is nucleophile which attacks on double bonded carbon. Pi electron gets delocalize to produce product by removing Tosyl alcohol (TsOH) HS H3C H-SH CH S-O H3C but-2-ene-2-thiol HaC c) lodine is leaving group which lost to form carbocation. On this carbocation,methoxy group attacks either from backside or frontside to produce racemic mixture. ( carbocation is having tertrahedral structure and free to attack fromboth side.) This is S..1 reaction o--сн Нас Hac CH CH CH3 KI Нас 3-iodo-2-methylpentane d) First bromine is lost to form carbocation. Attackof nucleophile rearrangement takes place to form 3-methoxy-2-methylpentane product. This is S1 reaction CH 8r CH H2C CH Нас -B HaC 1-ethoxy-3-methylbut-2-ene 3-bromo-3-methylbut-1-ene e) In this reaction, first chlorine lost to for secondary carbocation. This is less stable than tertiary carbocation, therefore, secondary carbocation is converted to tertiary carbocation by hydride transfer. Then on this tertiary carbocation, nucleophile attacks to produce product. CH CH3 CH CI -CI HCI Secondary carbocati ion tertiary carbocation HaC S CH S--CH CH This is Sy1 reaction methyl 1-methylcyclopentyl sulfide