Organic Chemistry II – Reac on Mechanisms and
Problem Sets/Organic Chemistry II | Lectures 1-38 | All
Course Material LATEST WITH COMPLETE SOLUTION
RATED A+
adding 1 mol NaNH2 to an alkyne
removes the H off the C and leaves two lone pairs and a nega ve charge
We use this so we can add things to the end of a triple bond (See pick) through an SN2 reac!on
t-buOK
Make an alkene from an alkane
a'acks least substuited carbon
How to form an epoxide from an alkane with Br
1. t-buOK
--- uses Br to form alkene
2. RCO3H
--- convert the alkene to an epoxide (RACEMIC)
N.B. this example uses dif chemicals
Br2, hv
Bromina!on of Alkanes
!. Alkane
2. Add Br to the most subs!tuited carbon
H3O+ excess and protec!ng group
This just means you take off the protec!ng group at the end
1. Br2
2. NaNH2 (2 or 3 mol)
,turns alkenes into alkynes
changes depending on whether its internal alkyne
Retrosynthesis of chair confirma!on to fragment
Even if there are mul!ple OHs, we know the one that was the DP is the one next to the O in the
ring
In chair confirma!on, we can see the stereochemistry of the subs!tuents (Wedged or dashed) if
it is poin!ng up or down
--- N.B. when we turn it from a ring into a line, the stereochemistry we keep is NOT the
wedged/dashes but whether it is R or S
NaOH, H2O
regioselec!ve
Markov
on the most hindered carbon
non markov
on the least hindered carbon
ATTACK OF THE NUCLEOPHILE
you can also write "make a bond"
When the nucleophile a'aches itself to the electrophile
1. BH3
2. H2O2, NaOH
add OH to least subs!tuted C on the alkene (non-markov)
Conc H2SO4
E1
alcohol to alkene
Write SN2 or
simultaneous a'ack of the nucleophile and departure of leaving group
Organometallic compounds
,compounds that contain carbon-metal bonds
Ex.
Hemoglobin has Fe
Chlorophyll has Mg
IMPORTANT: in almost all other bonds we look at (ex. C-O), the other atom is more
electronega!ve (O). With ORganiometallic compounds, the carbon is more electronega ve
than metal and has a par al - charge. Carbon is the nucleophile.
WE focus on
--- Grignard Reagents
--- Organolithium Reagents
--- Gilman Reagents
(all are nucleophiles)
Grignard and Organolithium are strong bases
FORMING AN EPOXIDE
Grignard reagent
Alkyl-MgBr
Prepara!on of Grignard Reagent
Mg, Ether
1) Start with any Haloalkane (can be primary, secondary, ter!ary, etc..)
2) Add Mg with Ether Solvent
3) Mg will replace the posi!on of the halogen
Organolithium reagents
Alkyl-Li
Prepara!on of Organolithium Reagent
2 Li, pentane
1) Start with any Haloalkane (can be primary, secondary, ter!ary, etc..)
2) Add 2 Li with Pentane Solvent
, 3) One of the Li will replace the posi!on of the halogen, and the other will form a bond with the
loose halogen
FORMS SIDE PRODUCT OF LiBr which is why we need 2 Li)
Gilman Reagent
(Alkyl)2-CuLi
The alkyl R group needs to be minimally sterically hindered, 4 op ons:
--- primary haloalkane
--- primary allylic haloalkane (the primary haloalkane is next to a C with a double bond
--- vinylic haloalkane (the carbon with the halogen also has a double bond
--- aroma!c haloalkane (A'ached to a ring??)
Prepara!on of Gilman Reagent
A) 2 Li, pentane
B) Cu, Ether
Start with 2 mol of Organolithium Reagent
1) Start with one of four Haloalkane
2) Add 2 Li with Pentane Solvent
3) One of the Li will replace the posi!on of the halogen, and the other will form a bond with the
loose halogen
x2
4) add CuI in Ether solvent to two copies of the O Reagents
--- Cu takes the place of one of the Li, and the other one binds to the free I
Grignard and Organolithium reagents react with
A)
Gilman Reagents don't react with
a) aLDEHYDES/kETONES (not nucleophilllic enough)
Nucleophilic Ring Opening of Epoxide using Grignard/Organolithium Reagent
A) add
Problem Sets/Organic Chemistry II | Lectures 1-38 | All
Course Material LATEST WITH COMPLETE SOLUTION
RATED A+
adding 1 mol NaNH2 to an alkyne
removes the H off the C and leaves two lone pairs and a nega ve charge
We use this so we can add things to the end of a triple bond (See pick) through an SN2 reac!on
t-buOK
Make an alkene from an alkane
a'acks least substuited carbon
How to form an epoxide from an alkane with Br
1. t-buOK
--- uses Br to form alkene
2. RCO3H
--- convert the alkene to an epoxide (RACEMIC)
N.B. this example uses dif chemicals
Br2, hv
Bromina!on of Alkanes
!. Alkane
2. Add Br to the most subs!tuited carbon
H3O+ excess and protec!ng group
This just means you take off the protec!ng group at the end
1. Br2
2. NaNH2 (2 or 3 mol)
,turns alkenes into alkynes
changes depending on whether its internal alkyne
Retrosynthesis of chair confirma!on to fragment
Even if there are mul!ple OHs, we know the one that was the DP is the one next to the O in the
ring
In chair confirma!on, we can see the stereochemistry of the subs!tuents (Wedged or dashed) if
it is poin!ng up or down
--- N.B. when we turn it from a ring into a line, the stereochemistry we keep is NOT the
wedged/dashes but whether it is R or S
NaOH, H2O
regioselec!ve
Markov
on the most hindered carbon
non markov
on the least hindered carbon
ATTACK OF THE NUCLEOPHILE
you can also write "make a bond"
When the nucleophile a'aches itself to the electrophile
1. BH3
2. H2O2, NaOH
add OH to least subs!tuted C on the alkene (non-markov)
Conc H2SO4
E1
alcohol to alkene
Write SN2 or
simultaneous a'ack of the nucleophile and departure of leaving group
Organometallic compounds
,compounds that contain carbon-metal bonds
Ex.
Hemoglobin has Fe
Chlorophyll has Mg
IMPORTANT: in almost all other bonds we look at (ex. C-O), the other atom is more
electronega!ve (O). With ORganiometallic compounds, the carbon is more electronega ve
than metal and has a par al - charge. Carbon is the nucleophile.
WE focus on
--- Grignard Reagents
--- Organolithium Reagents
--- Gilman Reagents
(all are nucleophiles)
Grignard and Organolithium are strong bases
FORMING AN EPOXIDE
Grignard reagent
Alkyl-MgBr
Prepara!on of Grignard Reagent
Mg, Ether
1) Start with any Haloalkane (can be primary, secondary, ter!ary, etc..)
2) Add Mg with Ether Solvent
3) Mg will replace the posi!on of the halogen
Organolithium reagents
Alkyl-Li
Prepara!on of Organolithium Reagent
2 Li, pentane
1) Start with any Haloalkane (can be primary, secondary, ter!ary, etc..)
2) Add 2 Li with Pentane Solvent
, 3) One of the Li will replace the posi!on of the halogen, and the other will form a bond with the
loose halogen
FORMS SIDE PRODUCT OF LiBr which is why we need 2 Li)
Gilman Reagent
(Alkyl)2-CuLi
The alkyl R group needs to be minimally sterically hindered, 4 op ons:
--- primary haloalkane
--- primary allylic haloalkane (the primary haloalkane is next to a C with a double bond
--- vinylic haloalkane (the carbon with the halogen also has a double bond
--- aroma!c haloalkane (A'ached to a ring??)
Prepara!on of Gilman Reagent
A) 2 Li, pentane
B) Cu, Ether
Start with 2 mol of Organolithium Reagent
1) Start with one of four Haloalkane
2) Add 2 Li with Pentane Solvent
3) One of the Li will replace the posi!on of the halogen, and the other will form a bond with the
loose halogen
x2
4) add CuI in Ether solvent to two copies of the O Reagents
--- Cu takes the place of one of the Li, and the other one binds to the free I
Grignard and Organolithium reagents react with
A)
Gilman Reagents don't react with
a) aLDEHYDES/kETONES (not nucleophilllic enough)
Nucleophilic Ring Opening of Epoxide using Grignard/Organolithium Reagent
A) add
