CHM 255 – Reaction Mechanisms

Question 1

deprotenated alkyne w/ primary alkyl halide

Answer 1

SN2 reaction

Question 2

deprotenated alkyne w/ secondary or tertiary alkyl halide

Answer 2

acts as base in E2 reaction

Question 3

hydrohalogenation (ex. HBr)

Answer 3

markovnikov addition

Question 4

HBr (the only hydrohalogenation) + peroxides + heat or light

Answer 4

break apart the double bond to form radicals

anti-Mark addition

Question 5

Br2 (bromination)

Answer 5

anti add (Br’s are added to opposite faces of the broken)

Question 6

reaction of alkyne with strong base (eg. NaNH2, NaH, LDA)

Answer 6

deprotenation (can have multiple equivalents)

Question 7

reaction of dibromides with NaNH2

Answer 7

can use 2 equivalents of NaNH2 to do 2 E2 reaction mechanisms and form an alkyne

Question 8

how to turn a triple bond into an alkene or alkane

Answer 8

reduction –> add H’s

1) hydrogenation (H2, Pd) –> triple bond gets reduced all the way to alkane

2) H2 w/ Lindlar’s catalyst –> reduces triple bond only. Triple bond –> double bond –> syn addition, cis (Z) alkene

3) Na, NH3 –> reduces triple bond only. Triple bond –> double bond –> anti addition, trans (E) alkene

Question 9

result of reaction b/n alkyne and H2, Lindlar’s

Answer 9

cis alkene
Z

Question 10

result of reaction b/n alkyne and Na, NH3

Answer 10

trans alkene
E

Question 11

result of reaction b/n alkyne and H2, Pd

Answer 11

alkane