O Chem 331 Exam 4 Final Exam
Questions and All Correct Answers.
How to make C-C bond for synthesis problems - Answer start with alkyne
deprotonate (add strong base, usually NaNH2)
add alkyl halide
How to make cis alkene from alkyne - Answer H2 and Lindlars catalyst
How to make trans alkene from alkyne - Answer Na metal in liquid NH3
alkene hydrogenation - Answer - h2 and metal (pd/pt)
-break pi bond, add H to each carbon
-syn addition
alkene hydrohalogenation-- just HX - Answer - HX (HCl, HBr)
- break pi bond, put H on less substituted carbon (C)
- carbocation forms at more substituted C
-be careful of hydride shift and carbocation rearrangement
-halogen (X) adds to most substituted C
alkene hydrohalogenation-- HX in ROOR - Answer - anti markov
- break pi bond, add X to less substituted C
- add H to more sub. C
alkene Halogenation - Answer - X2 in non reactive solvent (CH2Cl, etc)
- break pi bond, put X on both Cs that were in bond
- anti: add X to different faces
alkene halohydrin - Answer -X2 in reactive solvent (H2O)
-add X to less sub. C
- cut off one H from solvent and add the rest to more sub. C side
Alkene Acid catalyzed hydration - Answer -H2O; React in aqueous sulfuric acid, make alcohol
-break pi bond, add H to less sub. C
, -carbocation intermediate forms on more sub C, rearrange if needed
- OH added to C that had final carbocation placement
alkene oxymercuration - Answer -Hg(OAC)2, H20 in NaBH4
- markovnikov but no carbocation intermediate
- break pi bond add H to less sub C
-add OH to more sub C
-if showing chirality, add H and OH to different faces
alkene alkoxymercuration - Answer - Hg(OAc)2, ROH in NaBH4
-break pi bond, add H to less sub C
- add O-R to more sub. C
- if showing chirality, add H and OR to different faces
alkene Hydroboration - Answer - BH3, THF and NaOH/H2O2/H2O
- break pi, add H to more sub C
- add OH to less sub C
- syn addition
alkene epoxidation - Answer - Extra O in reactant (mPCBA, RCO3H)
-break pi bond in the middle, add an O in between both C to make 3 member ring
-if reacting with H3O+ too, add OH to both C in the bond (anti addition)
Alkene Dihydroxylation - Answer - strong oxidizing agent, weak conditions (KMnO4,
cold/dilute)
- or OsO4
- break pi bond, add OH to each C, syn
alkene oxidative cleavage- KMnO4, hot conditions - Answer - spilt pi bond down middle, add
O to both sides of the break
- other side of break becomes carboxylic acid
alkene ozonolysis- reductive conditions - Answer - O3, DMS [ (CH3)2S ]
- cleave pi bond, add O to less sub. C
- add H to more sub. C
Questions and All Correct Answers.
How to make C-C bond for synthesis problems - Answer start with alkyne
deprotonate (add strong base, usually NaNH2)
add alkyl halide
How to make cis alkene from alkyne - Answer H2 and Lindlars catalyst
How to make trans alkene from alkyne - Answer Na metal in liquid NH3
alkene hydrogenation - Answer - h2 and metal (pd/pt)
-break pi bond, add H to each carbon
-syn addition
alkene hydrohalogenation-- just HX - Answer - HX (HCl, HBr)
- break pi bond, put H on less substituted carbon (C)
- carbocation forms at more substituted C
-be careful of hydride shift and carbocation rearrangement
-halogen (X) adds to most substituted C
alkene hydrohalogenation-- HX in ROOR - Answer - anti markov
- break pi bond, add X to less substituted C
- add H to more sub. C
alkene Halogenation - Answer - X2 in non reactive solvent (CH2Cl, etc)
- break pi bond, put X on both Cs that were in bond
- anti: add X to different faces
alkene halohydrin - Answer -X2 in reactive solvent (H2O)
-add X to less sub. C
- cut off one H from solvent and add the rest to more sub. C side
Alkene Acid catalyzed hydration - Answer -H2O; React in aqueous sulfuric acid, make alcohol
-break pi bond, add H to less sub. C
, -carbocation intermediate forms on more sub C, rearrange if needed
- OH added to C that had final carbocation placement
alkene oxymercuration - Answer -Hg(OAC)2, H20 in NaBH4
- markovnikov but no carbocation intermediate
- break pi bond add H to less sub C
-add OH to more sub C
-if showing chirality, add H and OH to different faces
alkene alkoxymercuration - Answer - Hg(OAc)2, ROH in NaBH4
-break pi bond, add H to less sub C
- add O-R to more sub. C
- if showing chirality, add H and OR to different faces
alkene Hydroboration - Answer - BH3, THF and NaOH/H2O2/H2O
- break pi, add H to more sub C
- add OH to less sub C
- syn addition
alkene epoxidation - Answer - Extra O in reactant (mPCBA, RCO3H)
-break pi bond in the middle, add an O in between both C to make 3 member ring
-if reacting with H3O+ too, add OH to both C in the bond (anti addition)
Alkene Dihydroxylation - Answer - strong oxidizing agent, weak conditions (KMnO4,
cold/dilute)
- or OsO4
- break pi bond, add OH to each C, syn
alkene oxidative cleavage- KMnO4, hot conditions - Answer - spilt pi bond down middle, add
O to both sides of the break
- other side of break becomes carboxylic acid
alkene ozonolysis- reductive conditions - Answer - O3, DMS [ (CH3)2S ]
- cleave pi bond, add O to less sub. C
- add H to more sub. C
