Exam II SN1, E1, SN2, E2 Reactions Markovnikov Addition Ant-Markovnikov Addition Reaction Mechanisms Hoffman and Saytzeff Eliminations Enantiomers and Diastereomers
Exam II
SN1, E1, SN2, E2 Reactions
Markovnikov Addition
Ant-Markovnikov Addition
Reaction Mechanisms
Hoffman and Saytzeff Eliminations
Enantiomers and Diastereomers
SN1 Reactions:
By-Products - Whenever an SN1 reaction occurs there is always the possibility that an
E1 by-product will form. This occurs if the nucleophile does not get to the carbocation
soon enough. Therefore, if you see a reaction with SN1 conditions always assume that
some E1 minor product will form.
Racemic Mixtures - In SN1 reactions you also have the possibility of making a racemic
mixture of products – that is, left and right hand versions of the same molecule. Always
check to see if the leaving group is on a chiral carbon, if so, then a racemic mixture will
be made.
Rearrangements – It is also possible for SN1 reactions to rearrange. Carbocations want
to be on the most stable carbon, and this means 3 if it is available. Therefore
carbocations will rearrange themselves to place the positive charge onto the most stable
carbon ONLY IF the most stable carbon is right next door.
E2 Reactions:
Big Bases – For an E2 reaction to take place you must use a big base. Classically this
means using the t-butoxide ion (t-ButO-) but other large bases can be used (more on this
later). You do not want to use a base that is so small that an SN2 reaction could occur. If
you look carefully, you will see that the conditions of an E2 and an SN2 reaction are
nearly identical except for the size of the base. So large bases must be used for E2
reactions.
Hoffman vs. Saytzeff - E2 reactions make double and triple bonds by removing an HX
from a molecule. But which HX? As can be seen below, you may have a couple of
choices;
H3C C C2H5
Cl
H
KOH, H2OH3C C C2H5
OH
H
H3C C C2H5
H
OH
and
H3C C C
CH3
H
CH3
H
Cl
H3C C C
CH3
H
CH3
H
+
HydrideShift
H3C C C
CH3
CH3
H
H
+H3C C C
CH3
CH3
H
H
OH-
OH
H3C C C
CH3
H
C
Cl
H
H
H
H
HoffmanProduct
SaytzeffProduct
The Saytzeff is the “inner” product and the Hoffman is the “outer” product. Of the two,
Saytzeff is the most stable because it produces a double bond with more carbons around
it which can feed electrons to the double bond (by induction).
It is possible to select between Saytzeff and Hoffman products by selecting the proper
sized base. Hoffman products are always made when very large bases like t-ButO- are
used. Large bases are simply to big to grab inner hydrogens and do an elimination. Big
bases are force to attack on the outside of the molecule where there is less hinderance,
thus the Hoffman product is formed.
To get the Saytzeff product a smaller base must be used, but not one that is so small that
you risk the possibility of SN2 product formation. For this purpose EtO- is often the base
of choice. The EtO- ion sits between the region of large and small bases and will do
either E2 or SN2 reactions depending on the substrate used. As long as the substrate is
hindered enough, E2 reactions will predominate, but there is always the risk of SN2 by-
products.
Proper Orientation - Perhaps the most important aspect of E2 elimination is the need
forproper orientation of the molecule. E2 reactions occur anti which means that the
hydrogen being attacked and the halogen that is leaving must be on opposite sides of the
molecule.
H3C C C
CH3
H
C
Cl
H
H
H
HIncoming Base
-
Syn - Interferes with the Cl
- trying to leave (repulsion)
Anti - No interferancewith the Cl
-
The reason why this orientation is important is that if the base is on the same side as the
leaving group (syn attack) then the negative charge of the base, and the negative charge
of the leaving group will repulse one another and keep a reaction from occurring. In
addition, since the hydrogen and the halogen must be on opposite sides of the molecule,
you may have more than one hydrogen to choose from when doing the elimination. Not
all hydrogens are equal. In order to choose the right hydrogen, you must draw the most
stable Newman projection of the molecule. Consider the molecule below.
H3C C C
CH3
H
C
Cl
H
H
H
H
HoffmanSaytzeff
Base-
H3C C C
CH3
CH3
H
H3C C C
CH3
C
H
H
HH
Saytzeff "Inner" Product
Hoffman"Outer" Product
Depending on the orientation of the molecule only one of the two possible products are
formed, but which one? To know this, we must draw the Newman projection and then
rotate the molecule so that the hydrogen is opposite the halogen.
By appropriate rotation and elimination you can see that the final product will be cis-3-
methyl-2-butene (or Z-3-methyl-2-butene). You cannot predict whether the product will
be cis or trans (E or Z) unless you draw the Newman projection and then do the
elimination.
E1 Reactions:
E1 reactions are by the far the rarest reactions among this group. The reaction requires
that there be a protic solvent and no nucleophile - a condition difficult, but not
impossible, to satisfy.
Most protic solvents are also weak nucleophiles. As we have seen, solvents like water
and alcohol can are nucleophilic enough to give SN1 by-products even under the best of
conditions. The trick is to use a protic solvent that is also such a poor nucleophile that
the nucleophile does not want to react. This can be done in two ways, make it big, and
make it a very weak base. As it turns out, strong acids, like sulfuric acid (H2SO4) and
phosphoric acid (H3PO4), fit this profile.
The sulfate and phosphate ions are very large and very poor nucleophiles as are the
conjugate bases of most strong acids. Even relatively weak acids like acetic acid can be
used, because the acetate ion is large and weakly basic. Most of the time, strong acids are
used to do E1 eliminations. This is not exclusive of course – water and other protic
solvents could be used, but you run the risk of making large amounts of SN1 by-product
by using these solvents. As long as no strong nucleophile is present, solvents like water
and alcohol could also be used. A typical E1 elimination is shown below. Note: The
most stable product is always formed. For E1 reactions this always means trans.
C C C C
Cl
H
CH3
H
C
C
C C
CH
CH3
C
C
C C
C
H CH3
C
orE2
Saytzeff
cis trans
C-C
H
H3C
H
Cl CH3H3C C C C
Cl
H
CH3
H
C
C-C
H3C H
CH3
H
Cl
Put the halogenand hydrogen opposite
one another
C-C
H3C
CH3
H
Eliminate the HCland form a double bond
C
C C
C
H CH3
C
The final product has a cis double bond
C C C C
OH
H
CH3
H
CH2SO4, H3PO4 or both
C
C C
CH
CH3
C
+ H2O
About Solvents….
By now, I am sure that you are very confused about solvents and which solvent to use
with which reaction. Some of it is common sense and some of it is experience, but there
is much more to the common sense than the experience. Let me give you some
examples.
Alcohols and Alkoxides
By far the most common solvent/nucleophile combination is the alcohol/alkoxide
combination. Alkoxides (methoxide, ethoxide, t-butoxide, etc) are all made from their
respective alcohols based on the following reaction;
The point is that the alkoxide is always made from the alcohol so both are present in
solution – the alcohol being the solvent and the alkoxide being the nucleophile/base.
Common pairs are given below.
Solvent Nucleophile/base Also known as;
CH3OH CH3ONa (MeOH and MeO-)
C2H5OH C2H5ONa (EtOH and EtO-)
t-ButOH t-ButOK (t-ButOH and t-ButO-)
These solvent/base pairs are commonly used in SN2, E2, and even SN1 reactions.
Strong Acids
Strong acids are common solvents used in E1 reactions but they are also used in SN1, and
even SN2 reactions (but never E2). Now why would a strong protic solvent like H2SO4
be needed in a reaction that prefers aprotic solvents (like SN2 reactions)? The answer is
really very simple. Acids are commonly used to get rid of OH groups by turning them
into good leaving groups (water!). So you frequently see acids used whenever the
leaving group is an OH – even on SN2 reactions as shown below.
R OH + 2 Na(s)2 R O-
2 + H2
C C C
OH
H+ (H2SO4)C C C
OH H+
Br-
C C C
Br
+ H2O
SN1, SN2, E1, and E2 Reaction Conditions
Reaction Type Substrate Nucleophile/Base Solvent Leaving Group
SN2 1o, unhind 2
o Small strong Aprotic Good LG
SN1 3o, hind 2
o Nuc
- present Protic Good LG
E2 1o, 2
o, or 3
o Large base Aprotic Good LG
E1 3o, hind 2
o No base or nuc
- Protic Good LG
Small Strong Bases
(Nucleophiles):
OH-
CH3O- (MeO
-)
C2H5O- (EtO
-)
CH3-
C2H5-
I-
H-
NH2-
CH3NH-
Big Bulky Bases:
t-ButO-
isoPrO-
Protic Solvents
H2O
Alcohols – MeOH, EtOH
Organic Acids – HAC
Inorganic Acids – H2SO4, H3PO4
Aprotic Solvents
Acetone
THF
Diethyl ether
DMSO
Methylene Chloride
Mechanisms:
SN2 Mechanism:
Note: Walden
inversion
SN1 Mechanism:
Note: Racemic mixtures are possible
E1 Mechanism:
Note: Racemic mixtures are possible
E2 Mechanism:
C Cl
H
H
HOH- CHO
H
H
H Cl-+
H C C
H
Cl
H
H
HBase-
H
C C
H H
H
+ HBase + Cl-
Details…details…
SN2 Reactions:
Solvent – SN2 reactions prefer the use of aprotic solvents but that does not mean that
protic solvents cannot be used – it simply means that the reaction will go slower if a
protic solvent is used, but that should not hinder its use. Many reactions will require the
use of a protic solvent because of the nature of the nucleophile used.
A large number of nucleophiles are the conjugate bases of alcohols. These nucleophiles
are made by adding pure sodium metal to the alcohol according to the following reaction;
2 Na(s) + 2 ROH 2 RO- Na
+ + H2
The nucleophile (RO-) is produced in this reaction and then used to substitute for other
poorer leaving groups. BUT because of the nature of the nucleophile, the solvent must be
the alcohol from which it was made. Therefore you must use the corresponding alcohol
for each of the following nucleophiles;
Nuc- Alcohol
CH3O- & CH3OH
C2H5O- & C2H5OH
t-ButO- & t-ButOH
isoPrO- & isoPrOH
So, if you want to use a nucleophile that is made from an alcohol, you must use the
alcohol as the solvent. The problem of course is that alcohols are protic, but this should
not be cause for concern because they will work just fine even if they do slow down the
reaction.
For other nucleophiles like OH- (really NaOH), you can go into the stock room, get it,
and throw it into any solvent you like (like THF or diethyl ether). This makes it easy.
But most of the time this is not the case.
Markovinikov Additions to Alkenes
C C CH+
C C C
H
+
Cl-
C C C
H
Cl
C C CBr+
C C CBr
-
C C C
Br
Br
Br+
C C CH+
C C C
H
+
H2OC C C
H
OH H+
C C C
H
OH
+ H+
C C CBr+
C C COH-
C C C
Br
OH
Br+
C C CH+
C C C
H
+
CH3OHC C C
H
OH3C H+
C C C
H
OCH3
+ H+
HX Addition
Halogen Addition
Hydration - Addition of Water
Alcohol Addition
Halohydrin Reaction
C C CHgOAc
+
C C CH2O
C C C
HgOAcHgOAc+
H+C C C
H2OC C C
OH
O
O
Oxymercuration/Deoxymercuration
Epoxide RingOpening - Acid
OH H+
NaBH4C C C
H
OH
C C CHgOAc
+
C C CCH3OH
C C C
HgOAcHgOAc+
Alkoxymercuration/Dealkoxymercuration
OH3C H+
NaBH4C C C
H
OCH3
H
+
C C C
O
H H+
C C C
OH
OH
C C C
OH
OH
Epoxide RingOpening - Base
C C COH
-
O
C C C
O-
OHH2O
+ OH-
Anti-Markovinikov Additions
C C C
CO O OH
Cl
meta-chloroperoxybenzoic acid(MCPBA)
Heat or Light
CO O
+ OH
Cl
BrC C C
Br
OH + HBr H2O + Br
C C C
Br
HBrC C C
Br
H
+ Br
Chain Initiation
Chain Propagation
Chain Termination - Any two radicals (not shown)
Anti-Markovinikov HX Addition
Other Alkene Reactions
C C C C C C C C C
Epoxide Formation
O
OH
O
Cl
C
C
C
C C C
O
OH
O
Cl
C
C
C
O
OH
O
Cl
C
C
C
O
OH
O
Cl
Epoxide
m-chlorobenzoic acid
CH2
CH2
CH2
(other products possible)
Carbene Addition
meta-chloroperoxybenzoic acid
Catalytic Hydrogenation
H2 gas
Surface of Catalyst(Typically Platinum)
Surface of Catalyst(Typically Platinum)
H H
Surface of Catalyst(Typically Platinum)
H H
CCC
Surface of Catalyst(Typically Platinum)
H H
CCC
Alkane Produced
Str
on
g A
cids
Only
Str
on
g A
cid a
nd
Hal
ide
Nucl
eoph
ile
and
Ap
roti
c S
olv
ent
Nucl
eoph
ile
and
Pro
tic
Solv
ent
Bas
e an
d P
roti
c S
olv
ent
Pro
tic
Solv
ent
On
ly
Su
bst
rate
Unh
ind 2
o
3o
Hin
d. 2
o
Alc
ohol
Hal
ide
Alc
ohol
Hal
ide
Str
ong A
cids
Only
Str
on
g A
cid a
nd H
alid
eN
ucl
eoph
ile
and
Ap
roti
c S
olv
ent
Nucl
eoph
ile
and
Pro
tic
So
lven
tB
ase
and
Pro
tic
Solv
ent
Str
on
g A
cid a
nd H
alid
eN
ucl
eop
hil
e an
d P
roti
c S
olv
ent
Bas
e an
d P
roti
c S
olv
ent
Pro
tic
Solv
ent
Only
Sn2
Sn2
E2
E1 (
Sn
1)
Sn
1 (
E1
)E
2E
1 (
Sn
1)
Sn
1 (
E1
)
Solv
ent
Com
bin
atio
ns
1) Please supply the product for each of the following reactions.
C C
C
CH3
C C
C
C
Cl
C
ClH3C
H
H
CH3C
H
C2H5
Br
CH3
H
C C
C C
CH3
OH
H
HCl
Hg(OAc)2CH3OH, NaBH4
EtO-/EtOH
KI, Ether
EtO-/EtOH
O3, (CH3)2S
OsO4, H2O2
con. H2SO4
con. H3PO4
Heat
CH3
C C
C2H5
CH3
H
Br
H3C
H
C C C C1, Cl2, hv2. tButO-, tButOH3. KMnO4, H+, H2O
H2O, Br2
NaEtO, EtOH
C C C C
CH3
HBr, MCPBA
C C C C
CH3
MCPBA
Cl
CH3
HAc, Heat
C C C
1. Hg(OAc)2
2. C2H5OH
3. NaBH4
CH3
C C C C
C
O
C C
OH
C C C C
Br
C C C
Cl
CH3
C C C C
Cl
C
Cl
CH3
C C C
C
Cl
C C C C
C
C
C C
C
HCl
HBr
NaEtO, EtOH
2 NBS2 tButOK, tButOH
IsoProK, IsoProH
KOH, THF
NBS
HCl, MCPBA
1) KOH2) H2SO4, Heat
Br2, CH3OH
KMnO4
H2O, H2SO4
PBA
KI, EtOH
NaEtO, EtOH
KMnO4, H2SO4, H2O
CH3
C C
C2H5
CH3
H
Br
H3C
H
C C C C
C C C C
CH3
C C C C
CH3
Cl
CH3
1, Cl2, hv2. tButO-, tButOH3. KMnO4, H+, H2O
H2O, Br2
NaEtO, EtOH
C C C
HBr, MCPBA
MCPBA
HAc, Heat
1. Hg(OAc)2
2. C2H5OH
3. NaBH4
2) Circle the type of reaction occurring in each of the following. If more that one
reaction type occurs label the major and minor product.
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
C C C
OH
C C C
CH3
Br
Cl
POCl3
EtOHNaEtO
MeOHMeOK
Cl
CH3
O
C
Cl
HAc, Heat
H2SO4, H2O
KOH, EtOH
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
C C C
C
Cl
E2
SN1 SN2 E1 E2tButOH, Heat
Cl
Cl
C C C
Cl
C
CH3
Br
C C C OH
KI, Ether
MeOH, Heat
CH3ONa, CH3OH
HI
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
SN1 SN2 E1 E2
3) Please give the R,S and D, L designation for each of the following compounds,
R,S _______ _______ _______
D,L _______ _______ _______
3b) Which are enantiomers and which are diastereomers?
Enantiomers = Diastereomers =
4) Please draw the complete mechanism for the Markovnikov addition of HCl to 3-
methyl butene.
5) Please give the complete mechanism of the halohydrin reaction caused by reacting
3-methylbutene with water and bromine.
6a) Please draw the product of the Saytzeff elimination of 3R, 4S 3-chloro-4-methyl
hexane.
7) Please give the product of the Saytzeff elimination of HBr from the following
compound. Show your work.
8) Please draw the complete mechanism of the E1 elimination of 2-methylcyclohexanol
using H3PO4 and heat.
9) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3-
methyl pentene.
10) Please give the complete mechanism of the anti-Markovinikov addition of HBr to
butene.
11) Please give the mechanism for the formation of both products made by the reaction
of t-butyl alcohol with HCl.
COOH
C
C
CH3
CH3H
OHCl
CH3
C
C
OH
COOHH
CH3Cl
H
C
C
Cl
CH3HOOC
CH3HO
C C
Br
CH3 C2H5
HC2H5
H
12) Please draw all of the products from the reaction of trans 2 butene with water and
bromine (Halohydrin reaction).
13) Please give the complete mechanism of acid catalyzed epoxide ring opening using
epoxy propane.
14) Please draw the reaction diagram for the anti-Markovnikov addition of HCl with
PBA to butene, showing all reactants, products, intermediates and transition states. Do
not show any chain termination steps. The first step is endothermic and all subsequent
steps are exothermic.
15) Please draw the reaction diagram including all reactants, products, intermediates, and
transition states for the SN1 reaction that occurs between cyclohexanol and HCl. The
reaction is overall exothermic and the first step is rate determining.
16) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
17) What is the ratio of products formed by the free radical halogenation of hexane? Set
it up. You do not have to solve it.
18) Please calculate the percentage of 1º and 2º products formed by the free radical
chlorination of butane.
19) Predict the percentage of products made by the free radical chlorination of 1,1,4,4
tetramethylcyclohexane
1) Please supply the product for each of the following reactions.
C C
C
CH3
C C
C
C
Cl
C
ClH3C
H
H
CH3C
H
C2H5
Br
CH3
H
C C
C C
CH3
OH
H
HCl
Hg(OAc)2CH3OH, NaBH4
O3, (CH3)2S
OsO4, H2O2
CH3
C C
C2H5
CH3
H
Br
H3C
H
C C C C
C C C C
CH3
C C C C
CH3
Cl
CH3
C C C
EtO-/EtOH
KI, Ether
EtO-/EtOH
con. H2SO4con. H3PO4Heat
1, Cl2, hv2. tButO-, tButOH3. KMnO4, H+, H2O
H2O, Br2
NaEtO, EtOH
HBr, MCPBA
MCPBA
HAc, Heat
1. Hg(OAc)22. C2H5OH3. NaBH4
C C
Cl
C
OCH3
CH3
C C
C
C
C
I CH3
H
H
C C
CH3
H3C
C2H5
H
CH2O C C C
O
H
H
OH
CH3
OH
C C
OH
O
Br
H
CH3
OH
CC
H3C
CH3
C2H5
H
C C C C
CH3
Br
C C C C
CH3
O
CH3
C C
OC2H5
C
C + CO2
C C CHBr, PBA
CH3
H2O, Br2
C C CC
CH3
C C CC
Br
C
Br
C C CC
BrCH3ONa, CH3OH
OH
CH3
HI, DMSO
H
CH3
C C C C
C
C C C
C
C C C
OH
OH
CH3
1. Br2, light
2. tButOK, tButOH3. O3, (CH3)2S
1. PBA
2. H2SO4, CH3OH
Acetic Acid, Heat
1. Hg(OAc)2
2. H2O3. NaBH4
1) PBA
2) H2SO4, CH3OH
1) Br2, hv2) tButOK, tButOH3) NBS
Br2, H2O
KMnO4, NaOH, H2O
P/I2
EtOH,
H2SO4, KBr
C C C
Br
Br CH3
OH
CH2O C C C
O
H
OH CH3
OCH3
Br
OH
C C CC
OCH3
I
CH3
C C C C
C
Br
OH
C
Br
Br
CH3
No Reaction
C C C
I
OH OH
OH
OCH3
CH3
C C C C
C
O
C C C
OH
C C C C
Br
C C C
Cl
CH3
C C C C
Cl
C
Cl
CH3
C C C
C
Cl
C C C C
C
C C
C
HCl
HBr
NaEtO, EtO H
KOH, THF
NBS
HCl, MCPBA
Br2, CH3OH
PBA
KI, EtOH
NaEtO, EtO H
CH3
C C
C2H5
CH3
H
Br
H3C
H
C C C C
C C C C
CH3
C C C C
CH3
Cl
CH3
C C C
2 NBS2 tButOK, tButOH
IsoProK, IsoProH
1) KOH
2) H2SO4, Heat
KMnO4H2O, H2SO4
1, Cl2, hv2. tButO-, tButOH3. KMnO4, H+, H2O
H2O, Br2
NaEtO, EtOH
HBr, MCPBA
MCPBA
HAc, Heat
1. Hg(OAc)22. C2H5OH3. NaBH4
KMnO4H2SO4, H2O C C C CC
O
HO
C C C C
C
Cl
OH
Br
No Reaction
CCCC
C C C
OH
C C
C Br
Cl
CH3
H3CO
Br
Cl
C C
OH
O
CO
C
C
O
CH3
C C C
C
I
C C C C
OEt
Br CH3
OH
CC
C2H5
CH3
H3C
H
+ CO2C C
OH
O
C C C C
CH3
Br
C C C C
CH3
O
CH3
C C C
OC2H5
C
C
O
2) Circle the type of reaction occurring in each of the following. If more that one
reaction type occurs label the major and minor product.
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
C C C
OH
C C C
CH3
Br
Cl
POCl3
EtOHNaEtO
MeOHMeOK
Cl
CH3
O
C
Cl
HAc, Heat
H2SO4, H2O
KOH, EtOH
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
C C C
C
Cl
E2
SN1 SN2 E1 E2tButOH, Heat
Cl
Cl
C C C
Cl
C
CH3
Br
C C C OH
KI, Ether
MeOH, Heat
CH3ONa, CH3OH
HI
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
SN1 SN2 E1 E2
Major Minor
Major Minor
Major Minor
MajorMinor
MajorMinor
MajorMinor
3) Please give the R,S and D, L designation for each of the following compounds,
R,S __S,S__ __R,R__ __R,S__
D,L ___D___ ___L___ ___D___
3b) Which are enantiomers and which are diastereomers?
Enantiomers = AB Diastereomers = AC, BC
4) Please draw the complete mechanism for the Markovnikov addition of HCl to 3-
methyl butene.
5) Please give the complete mechanism of the halohydrin reaction caused by reacting
3-methylbutene with water and bromine.
6) Please draw the product of the Saytzeff elimination of 3R, 4S 3-chloro-4-methyl
hexane.
COOH
C
C
CH3
CH3H
OHCl
CH3
C
C
OH
COOHH
CH3Cl
H
C
C
Cl
CH3HOOC
CH3HO
H+C C C CH3
H
CH3
C C C CH3
H
CH3H
+C C C CH3
CH3H
H
+
Cl-
C C C CH3
CH3H
H Cl
Br+C C C CH3
H
OH-
CH3
C C C CH3
H
CH3Br
C C C CH3
H
CH3Br
OH
C C C C C C
Cl
H CH3
H
C C C C C C
Cl
H CH3
H
H CH3
HC2H5Cl
C2H5
CH3
HC2H5
Cl
H
C2H6
CH3
HC2H5
Cl
H
C2H6
C2H5
CH3
H
C2H5
Rotate theback of themolecule
The chlroine andthe hydrogen mustopposite one another
7) Please give the product of the Saytzeff elimination of HBr from the following
compound. Show your work.
8) Please draw the complete mechanism of the E1 elimination of 2-methylcyclohexanol
using H3PO4 and heat.
9) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3-
methyl pentene.
10) Please give the complete mechanism of the anti-Markovinikov addition of HBr to
butene.
C C HC2H5
H3C
H
C2H5
BrH Br
C2H5
HH3CC2H5
Br
C2H5H
H3C
H
C2H5
H
C2H5
H3C
C2H5
The bromine andthe hydrogen mustopposite one another
Rotate theback of themolecule
CH3
OH
H+
CH3
O
H
H
CH3
+ H2O
H H H HydrideShift
CH3
H
CH3
C C C C C
C
CO
O OH
light
CO
O OH+
HBr H2O + Br
Br + C C C C C
CBr
HBrC C C C C
CBr
H
+ Br
C C C C C
C
H+C C C C C
CH
H
HH
H
H
H
H H
C C C C C
CH H
H
H H
C2H5OH
C C C C C
CH H
H
H H O C2H5
H
C C C C C
CH H
H
H H O C2H5
H+ +
11) Please give the mechanism for the formation of both products made by the reaction
of t-butyl alcohol with HCl.
12) Please draw all of the products from the reaction of trans 2 butene with water and
bromine (Halohydrin reaction).
13) Please give the complete mechanism of acid catalyzed epoxide ring opening using
epoxy propane.
O
C C CH3
H+O
C C CH3
H
H2OC C CH3
OH
O H
H
C C CH3
OH
O H
+ H+
14) Please draw the reaction diagram for the anti-Markovnikov addition of HCl with
PBA to butene, showing all reactants, products, intermediates and transition states. Do
not show any chain termination steps. The first step is endothermic and all subsequent
steps are exothermic.
15) Please draw the reaction diagram including all reactants, products, intermediates, and
transition states for the SN1 reaction that occurs between cyclohexanol and HCl. The
reaction is overall exothermic and the first step is rate determining.
CO O OH
CO O OH
HO HCl
H2O + Cl
C C C C
Cl
C C C C
Cl
C C C C
ClH Cl
C C C C
Cl H
+ Cl
HCl
CO O OH + HCl
C C C C
Energ
y
Reaction Coordinate
Energ
y
Reaction Coordinate
OH
H
H
H
OH
H
H+
H
H
O
H
H
H
H
H
O
H
H
H
H
H
HH
H
HH
H
H
H
+ H2O
+ H+
16) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
17) What is the ratio of products formed by the free radical chlorination of hexane? Set
it up. You do not have to solve it.
X = 6 (1º) x 1.0
100-X 8 (2º) x 3.5
X = 17.65% 1º and 82.35% 2º
18) Please calculate the percentage of 1º and 2º products formed by the free radical
chlorination of butane.
X = 6 (1º) x 1.0
100-X 4 (2º) x 3.5
X = 30% 1º and 70% 2º
19) Predict the percentage of products made by the free radical chlorination of 1,1,4,4
tetramethylcyclohexane
X = 12 (1º) x 1.0
100-X 8 (2º) x 3.5
X = 30% 1º and 70% 2º
Energ
y
Reaction Coordinate
C C C + H+
C C C
H+
C C C
H
C C OH+
C C C
H
C C OH
C C C
H
C C O H
C C C
H
C C O H
C C C
H
C C O+ H
+
Chem 240 Name___________________
Exam #2 November 17, 1997
Closed Book Exam - No books or notes allowed. All work must be shown for full credit.
You may use a calculator.
Question Credit
1(12 )
2(28)
3(8)
4(26)
5(12)
6(14)
TOTAL
1) Please name or draw the structure of the following compounds.
D - 2 hydroxy propanoic acid
C
C
Cl
Cl
H3C
H3C
H
H
CH3
Cl HOH
H
CH3
C2H5
CH3
Cl
H
C C C C
C
Br2, H2O
H
CH3
1) Br2, h2) EtO-, EtOH3) NBS
H
CH3
H2SO4, KBr
C C C
C
OH
EtOH,
C C C
OH
P/I2
dil KMnO4, NaOH, H2O
1) PBA
2) H2SO4, CH3OH
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
3) Circle the type of reaction occuring in each of the following. If more that one reaction
type occurs label the major and minor product.
4) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
SN1 SN2 E1 E2
C C C
OH
C C C
CH3
Br
Cl
POCl3
EtOH
NaEtO
MeOH
MeOK
CH3
Br
MeOH, Heat
5) Please label the following compounds as R and S. Also, draw and label the missing
diastereomer/enantiomer.
A B C D
R,S ______ _______ ________ ________
5) Please indicate the enantiomer/diastereomer pairs below.
Diastereomers =
Enantiomers =
6) Using alkanes as your only carbon source please gives all steps in the synthesis of
methyl ethyl ketone (2 butanone).
COOH
C
C
CH3
H Cl
Cl H
Cl
C
C
H
H COOH
H3C Cl
H
C
C
CH3
HOOC Cl
H Cl
Chem 240 Name Answer Key
Exam #2 November 17, 1997
Closed Book Exam - No books or notes allowed. All work must be shown for full credit.
You may use a calculator.
Question Credit
1(12 )
2(28)
3(8)
4(26)
5(12)
6(14)
TOTAL
1) Please name or draw the structure of the following compounds.
Meso-2,3-dichlorobutane R-chloroethanol
2R,33-2-chloro-3-methylpentane D - 2 hydroxy propanoic acid
C
C
Cl
Cl
H3C
H3C
H
H
CH3
Cl HOH
H
CH3
C2H5
CH3
Cl
H
C C C C
C
Br2, H2OC C C C
C OH
Br
H
CH3
1) Br2, h2) EtO-, EtOH3) NBS
(Br)
CH2(Br)(Br)
Three possibleproducts
H
CH3
H2SO4, KBr
Br
CH3
C C C
C
OH
EtOH, No Reaction
C C C
OH
P/I2C C C
I
dil KMnO4, NaOH, H2O
OH OH
H H
1) PBA
2) H2SO4, CH3OH
OH
H
H
OCH3
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
3) Circle the type of reaction occuring in each of the following. If more that one reaction
type occurs label the major and minor product.
SN1 SN2 E1 E2
SN1 SN2 E1
SN1 SN2 E1 E2
E2
SN1 SN2 E1 E2
C C C
OH
C C C
CH3
Br
Cl
POCl3
EtOHNaEtO
MeOHMeOK
CH3
Br
MeOH, Heat
Major Minor
MajorMinor
4) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
5) Please label the following compounds as R and S. Also, draw and label the missing
diastereomer/enantiomer.
A B C D
R,S 2S, 3S 2R, 3S 2R, 3R 2S, 3R
5) Please indicate the enantiomer/diastereomer pairs below.
Diastereomers = AB, AD, BC, CD
Enantiomers = AC, BD
6) Using alkanes as your only carbon source please gives all steps in the synthesis of
methyl ethyl ketone (2 butanone).
C C C C
CBr2, light
C C C C
C
Br
t-ButO-, t-ButOH
C C C C
CO3, (CH3)2S
C C C C
O
Chem 240 Name___________________
Exam #2 November 22, 2000
CLOSED BOOK EXAM - No books or notes allowed. All work must be shown for full
credit. You may use a calculator.
Question Credit
1(20 )
2(32)
3(16)
4(12)
5(20)
TOTAL
1a) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3-
methyl butene.
1b) Please draw the product of the Saytzeff elimination of HBr from the following
compound. Two products are possible, but only one is made. Show how both could be
made and EXPLAIN which one is possible and why.
3) Circle the type of reaction occuring in each of the following. If more that one reaction
type occurs label the major and minor product.
4) The reactions using HBr and Br2/dark to alkenes are both Markovnikov additions.
Please show how the presence of H+ or Br
+ changes the product when each of them reacts
with 3 methyl butene.
5) Synthesize any two of the following compounds using alkanes as your only carbon
source. The number of steps required to make each compound is given.
Methyl ethyl ketone (2 butanone) (3 steps)
Propene-3-ol (4 steps)
Methyl ethyl ether (5 steps)
Chem 240 Name__Answer Key _____
Exam #2 November 22, 2000
CLOSED BOOK EXAM - No books or notes allowed. All work must be shown for full
credit. You may use a calculator.
Question Credit
1(20 )
2(32)
3(16)
4(12)
5(20)
TOTAL
1a) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3-
methyl butene.
1b) Please draw the product of the Saytzeff elimination of HBr from the following
compound. Two products are possible, but only one is made. Show how both could be
made and EXPLAIN which one is possible and why.
The most stable Newman projection puts
the C2H5 and the CH3 opposite each other
which forces the product to be trans.
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
3) Circle the type of reaction occuring in each of the following. If more that one reaction
type occurs label the major and minor product.
4) The reactions using HBr and Br2/dark to alkenes are both Markovnikov additions.
Please show how the presence of H+ or Br
+ changes the product when each of them reacts
with 3 methyl butene.
5) Synthesize any two of the following compounds using alkanes as your only carbon
source. The minimum number of steps needed to make each compound is given.
Methyl ethyl ketone (3 steps)
Propene-3-ol (4 steps)
Methyl ethyl ether (5 steps)
C C C C
1. Br2, h2. t-ButO-, tButOH3. O3, (CH3)2S
C
C C C C
O
C C C
1. Br2, h2. t-ButO-, tButOH3. NBS4. KOH, Ether
C C C OH
C CBr2, h
CH4
1. Br2, h2. KOH, Ether3. Na(s)
C C Br
CH3O-
C C O C