problem
DESCRIPTION
Problem. A symmetrical unknown compound A , C 8 H 16 , reacts with H 2 on a 1% Pt/C catalyst to form B (C 8 H 18 ). Treatment of A with acidic permanganate affords butanone only. Identify A and B. KMnO4, H3O +. Draw the missing structures. - PowerPoint PPT PresentationTRANSCRIPT
Problem
A symmetrical unknown compound A, C8H16, reacts with H2 on a 1% Pt/C catalyst
to form B (C8H18). Treatment of A with
acidic permanganate affords butanone only. Identify A and B.
CH3CCH2CH3
O
butanone
O
butanone
O
HH
H2
O3
A
B
KMnO4, H3O+
Draw the missing structures.
KMnO4, H3O+
?
KMnO4, H3O+
?O
OH
O
OH
O + O C O
Draw the structure of the main product(s) formed.
HCl
Addition to Conjugated Dienes
resonance forms of the allylic carbocation
The 1,2-addition product is typical Markovnikov.
The 1,4-addition product is due to the resonance forms of the allylic carbocation intermediate.
Draw a mechanism to explain the following reaction:
Hint: Why are there two products?
HCl
Cl
Cl+
The Hydride Shift
Opportunistic Carbocations!
-Terpinene, C10H16 (A), is a pleasant-smelling hydrocarbon that has been isolated from oil of marjoram. On hydrogenation over a palladium catalyst, -terpinene reacts with 2 equivalents of hydrogen to yield a new hydrocarbon, C10H20 (B). On reaction with acidic KMnO4, -terpinene yields the compounds below.
Propose a structures for and B. Outline all chemical reactions.
OO
OHHO
O
O
Alkynes
Reaction
Acidity
Synthesis
Complex of Acetylene
Bonds
Catalytic Hydrogenation
75 psi
H2 - 1%Pt on C
Hyddrogenation with Lindlar’s Catalyst forms cis Alkenes
H2 on a Poisoned Catalyst Prevents Over-Reduction
cis Alkenes
5-decyne
H2 / Pd on BaSO4
quinolineLindlar's catalyst H H
H2, 1%Pt on C
Addition of HX
CH3CH2C CHHBr
CH2CH3CH2C
BrHBr
CH3CH2CCH3
Br
Br
CH3CH2C=CH2
vinyl carbocationsp hybridized
Br2 Addition
C CH Br2C C
HBr
Br
C
Br
Br
C
Br
Br
H
Br2
Oxymercuration HydrationMarkovnikov
CH3CH2C CHHgSO4, H2SO4
H2OCH3CH2C=CH2
OH
an enol
CH3CH2CCH3
O
a ketone
Enol – Keto TautomerizationIntermolecular
3
OH
CH
HCH3CH2C
OH
CH
HCH3CH2C
OH
CH
HCH3CH2C
CH3CH2CCH3
O
Hydroboration HydrationAnti-Markovnikov
2) H2O2, NaOH
1) disiamyl borane
O
CH3CH2CH2CH
CHCH3CH2C
an enol
OH
CH3CH2CH=CH2
an aldehyde(sia)2BH
B
H
Draw the Products
C CH1) disiamylborane, THF
2) H2O2, NaOH
HgSO4, H2SO4 (aq)
C CH1) disiamylborane, THF
2) H2O2, NaOH
HgSO4, H2SO4 (aq)
CH2CH
CCH3
O
O
Acidity of Terminal Alkynes
Acetylide Formation
Alkylation of Acetylide IonsReaction with alkyl halides
CH3CH2CH2C C HNaNH2
in NH3(l)-78 C
o
CH3CH2CH2C C Na
CBr
H
HH
CH3CH2CH2C CCH3
SN2NH2
Multi-step Syntheses
HC CH Br?
Retrosynthetic AnalysisBegin with the Product
HC CH Br?
Fill in the Reagents
HC CH Br?
1) NaNH2, NH3
2) Br
H2, Lindlar's cat.
HBrROOR, h
Outline the synthetic steps. Indicate all necessary reagents
for each step.
5 Steps
1. NaNH2, NH3
2. CH3Br3. NaNH2, NH3
4. (CH3)2CHCH2Br5. H2, Lindlar's catalyst