Exam 2
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.
Cl
H3C
C
OH
C2H5
KOH, H 2O
H3C
C
H
H
C2H5 and
H3C
H
C
C2H5
OH
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.
CH3 H
H3C
C
H
C
CH3
Cl
H3C
C
CH3 H
CH3 H
CH3 H
Hydride
C
CH3 Shift
+
H3C
C
+
C
H
H
CH3
OH
-
H3C
C
C
CH3
OH H
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
CH3 Cl
H
C
C
C
H
H
H
Saytzeff
Product
H
Hoffman
Product
CH3 Cl
H3C
H
C
C
C
H
H
H
Saytzeff
CH3 H
Base-
H
H3C
C
C
CH3
CH3
H3C
Saytzeff
"Inner" Product
Hoffman
H
C
C
H
H
C
H
Hoffman
"Outer" Product
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 byproducts.
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.
Syn - Interferes with
the Cl- trying to leave (repulsion)
H3C
CH3 Cl
H
C
C
C
H
H
H
Incoming Base-
H
Anti - No interferance
with 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.
Cl
C
C
CH3
C
C
C
E2
C
Saytzeff
H
H
C
C
C
or
C
H
C
CH3
CH3
C
C
H
cis
C
C
trans
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.
Cl
H3C
C
H
CH3
C
C
C-C
CH3
Cl
H3C
C
H3C
HH
H
C-C
Cl
C-C
CH3
CH3
H
H3C
H
Put the halogen
and hydrogen opposite
one another
H
Eliminate the HCl
and form a double bond
C
C
C
C
H
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
H
H
C
C
C
H2SO4, H3PO4 or both
CH3
C
H
+ H2O
C
C
C
CH3
The final product
has a cis double bond
By appropriate rotation and elimination you can see that the final product will be cis-3methyl-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.
OH CH3
C
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;
2 R O + H2
2 R OH + 2 Na(s)
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
CH3OH
C2H5OH
t-ButOH
Nucleophile/base
CH3ONa
C2H5ONa
t-ButOK
Also known as;
(MeOH and MeO-)
(EtOH and EtO-)
(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.
H
C
C
+
H
O
OH
C
H+ (H2SO4)
C
C
C
Br-
C
C
Br
C + H2O
SN1, SN2, E1, and E2 Reaction Conditions
Reaction Type
SN2
SN1
E2
E1
Substrate
1o, unhind 2o
3o, hind 2o
1o, 2o, or 3o
3o, hind 2o
Nucleophile/Base
Small strong
Nuc- present
Large base
No base or nuc-
Small Strong Bases
(Nucleophiles):
OHCH3O- (MeO-)
C2H5O- (EtO-)
CH3C2H5IHNH2CH3NH-
Big Bulky Bases:
t-ButOisoPrO-
Protic Solvents
H2O
Alcohols – MeOH, EtOH
Organic Acids – HAC
Inorganic Acids – H2SO4, H3PO4
Aprotic Solvents
Acetone
THF
Diethyl ether
DMSO
Methylene Chloride
Solvent
Aprotic
Protic
Aprotic
Protic
Leaving Group
Good LG
Good LG
Good LG
Good LG
Mechanisms:
SN2 Mechanism:
H
H
OH-
H
C
HO
Cl
C
H
+
Cl-
H
H
SN1 Mechanism:
Note: Racemic mixtures are possible
E1 Mechanism:
Note: Racemic mixtures are possible
E2 Mechanism:
H
H
H
C
C
Cl H
Base-
H
H
C
H
H
+ HBase + Cl-
C
H
Note: Walden
inversion
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;
NucAlcohol
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
Cl
HX Addition
C
C
H+
C
C
C
Cl -
C
+
C
C
C
H
H
Br
Halogen Addition
C
C
Br+
C
C
C
Br-
C
C
C
C
Br
+
Br
H
+
H
C
C
OH
O
Hydration Addition of Water
C
C
C
H+
C
C
C
+
H2O
C
H3C
C
C
C
H+
C
C
C
+
C
CH 3OH
+
H
C
C
C
C
C
H
H
H
OH
Halohydrin Reaction
C
C
C
Br+
C
C
C
OH-
Br
+
C
C
C
H
+
Br
H
O
Oxymercuration/
Deoxymercuration
+
C
C
C
HgOA c
C
C
C
H2O
C
OH
C
Alkoxymercuration/
C
Dealkoxymercuration
C
C
HgOA c
C
C
C
C
CH 3OH
C
H
+
OCH3
C
NaBH4
C
C
+
H
H+
C
C
C
C
C
H2O
C
C
C
O+
O
OH
C
OH
Epoxide Ring
Opening - Base
C
C
C
O
OH
OH
OH
H2O
C
C
C
O-
C
C
C
OH
C
C
OH
H
-
C
H
O
C
C
HgOAc
H
C
H
O
Hg
OAc+
Epoxide Ring
Opening - Acid
C
HgOAc
H3C
+
NaBH4
C
Hg
OAc+
+ H+
OCH3
O
C
C
H
H
H
Alcohol Addition
C
+ OH-
+ H+
Anti-Markovinikov Additions
Anti-Markovinikov HX Addition
Chain Initiation
O
O
OH
O
C
O
C
Heat or Light
+ OH
Cl
Cl
meta-chloroperoxybenzoic acid
(MCPBA)
OH
+
C
C
HBr
H2O
+
Br
+
Br
Chain Propagation
C
Br
C
C
C
Br
H
C
C
C
HBr
C
Br
Chain Termination - Any two radicals (not shown)
C
C
Br
Other Alkene Reactions
Epoxide Formation
C
C
H
O
H
O
O
O
O
C
C
H
O
O
O
C
C
H
C
O
O
Epoxide
C
O
C
O
C C C
Cl
Cl
Cl
meta-chloroperoxybenzoic acid
Cl
m-chlorobenzoic acid
Carbene Addition
C
C
C
CH 2
C
C
C
C
C
C
(other products possible)
C
H2
C
H2
Catalytic Hydrogenation
Alkane Produced
H2 gas
H
Surface of Catalyst
(Typically Platinum)
H
Surface of Catalyst
(Typically Platinum)
C
C
H
H
C
Surface of Catalyst
(Typically Platinum)
C
C
H
H
C
Surface of Catalyst
(Typically Platinum)
E2
Base and Protic Solvent
Sn1 (E1)
E1 (Sn1)
E2
Base and Protic Solvent
Hind. 2o 3o
Strong Acid and Halide
Alcohol
Sn2
Nucleophile and Aprotic Solvent
Nucleophile and Protic Solvent
Halide
Strong Acids Only
Sn2
Strong Acid and Halide
Alcohol
Unhind 2o
E1 (Sn1)
Protic Solvent Only
Halide
Sn1 (E1)
Nucleophile and Protic Solvent
Strong Acids Only
Strong Acid and Halide
Nucleophile and Aprotic Solvent
Nucleophile and Protic Solvent
Base and Protic Solvent
Protic Solvent Only
Solvent Combinations
Substrate
1) Please supply the product for each of the following reactions.
C
C
HCl
C
H2O, Br2
CH3
Hg(OAc)2
CH 3OH, NaB H4
Br
C
H
CH3
Cl
CH3
C
H3C
H
NaEtO, EtOH
C2H5
-
C
C
C
C
EtO /EtOH
C
H
H3C
Cl
CH3
Br
H
C
C
C
C
1, Cl2, hv
2. tButO-, tButOH
3. KMnO4, H+, H2O
C
C
C
C
HBr, MCPBA
C
MCPBA
CH3
-
EtO /EtOH
H
C
C
KI, Ether
H
C2H5
H3C C
C
C
C
C
CH3
O3, (CH 3)2S
C
Cl
HAc, Heat
CH3
OsO4, H2O2
CH3
OH
H
con. H2SO4
con. H3PO4
Heat
C
C
C
1. Hg(OAc)2
2. C2H5OH
3. NaBH4
C
C
HBr, PBA
C
C
C
C
C
Br2, H2O
C
H2O, Br2
H
1) Br2, hv
2) tButOK, tButOH
3) NBS
CH3
CH3
1. Br2, light
C
C
C
C
2. tButOK, tButOH
3. O3, (CH3)2S
H2SO4, KBr
CH3
1. PBA
2. H2SO4, CH3OH
CH3
OH
EtOH, 
C
C
C
C
Br
C
C
C
C
OH
Acetic Acid, Heat
C
C
P/I2
C
C
1. Hg(OAc)2
2. H2O
3. NaBH4
Br
1) PBA
Br
CH 3ONa, CH3OH
C
KMnO 4, NaOH, H 2O
C
C
C
OH
HI, DMS O
CH3
2) H2SO4, CH3OH
KMnO 4, H2SO4, H2O
CH3
C
C
C
H2O, Br2
CH3
HCl
C
C
Br
HBr
CH3
H C
H3C
C
C
C
H
NaEtO, EtOH
C2H5
O
OH
C
C
NaEtO, EtOH
C
2 NBS
2 tButOK, tButOH
C
C
C
1, Cl2, hv
2. tButO-, tButOH
3. KMnO4, H+, H2O
C
C
C
HBr, MCPBA
CH3
Br
IsoProK, IsoProH
C
C
C
C
C
Cl
C
C
KOH, THF
C
C
C
C
C
C
MCPBA
CH3
NBS
C
Cl
HAc, Heat
HCl, MCPBA
CH3
Cl
C
C
CH3
C
C
1) KOH
2) H2SO4, Heat
C
Cl
Br2, CH3OH
KMnO 4
H2O, H2SO4
CH3
PBA
Cl
C
C
KI, EtOH
C
C
C
C
C
C
C
NaEtO, EtOH
C
C
C
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.
Cl
KI, Ether
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
EtOH
NaEtO
SN1
SN2
E1
E2
MeOH
MeOK
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
Cl
C
C
C
C
CH 3ONa, CH3OH
Cl
CH3
MeOH, Heat
Br
C
C
C
OH
HI
OH
POCl3
C
C
C
Cl
CH3
C
C
C
Br
CH3
HAc, Heat
Cl
O
H2SO4, H2O
Cl
KOH, EtOH
C
Cl
C
C
C
C
tButOH, Heat
3) Please give the R,S and D, L designation for each of the following compounds,
COOH
CH3
H
H
C
CH3
H
C
COOH
Cl
C
OH
Cl
C
CH3
CH3
HOOC
C
CH3
HO
C
CH3
OH
Cl
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 3methyl butene.
5) Please give the complete mechanism of the halohydrin reaction caused by reacting
3-methyl butene 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.
C H3
C 2 H5
C C
C 2 H5
H
H
Br
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 3methyl 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.
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.
Cl
C
C
HCl
C
C
C
Hg(OAc)2
CH3OH, NaBH4
C
C
Br
C
EtO-/EtOH
C
C
Br
H
EtO-/EtOH
C
C
C2H5
C
C
C
C
C
H3C
C2H5
1, Cl2, hv
2. tButO-, tButOH
3. KMnO4, H+, H2O
C
C
OH
C
HBr, MCPBA
Br C
CH3
C
C
C
C
MCPBA
C
C
CH3
C
C
O
H
CH2O
C
CH3
O
C
C
C
H3C
O3, (CH3)2S
C
C
CH3
C
H
CH3
CH3
H
CH3
OH
NaEtO, EtOH
C2H5
H
I
H
C2H5
H
O
C
KI, Ether
Cl
H
CH3
C
C
H
H3C
C
H3C
C
C
C
Br
H
CH3
C
H
OCH3
C
H3C
CH3
CH3
CH3
Cl
C
H2O, Br2
C
C
C
CH3
C
H
C
Cl
HAc, Heat
OsO4, H2 O2
H
CH3
CH3
CH3
CH3
OH OH
OH
H
con. H2SO4
con. H3PO4
Heat
C
C
C
1. Hg(OAc)2
2. C2H5OH
3. NaBH4
C
C
C
OC2H5
C
Br
Br
HBr, PBA
C
C
C
C
C
C
C
C
C
C
Br2, H2O
C
C
Br
H2O, Br2
CH 3
CH 3
C
C
C
OH
H
C
1) Br2, hv
2) tButOK, tButOH
3) NBS
OH
CH 3
C
C
C
C
2. tButOK, tButOH
3. O3, (CH3)2S
Br
O
1. Br2, light
CH 2O
C
C
Br
C
H2SO4, KBr
H
CH 3
OH CH 3
1. PBA
CH 3
OH
EtOH, 
2. H2SO4, CH3OH
C
CH 3
C
OCH 3
C
C
No Reaction
C
Br
C
C
C
C
OH
Acetic Acid, Heat
C
C
I
P/I2
C
C
C
C
C
1. Hg(OAc)2
Br
KMn O4, NaOH, H 2O
2. H2O
3. NaBH4
Br
OH
OH OH
OH
Br
CH 3ONa, CH3OH
C
C
C
C
C
C
C
C
OCH 3
OH
HI, DMSO
CH 3
CH 3
I
1) PBA
2) H2SO4, CH3OH
OCH 3
O
O
KMn O4
H2SO4, H2O
C
C
C
C
C
C
C
C
OH
C
Br
H
Br
CH 3
C
C
H 3C
H
H
NaEtO, EtOH
C2 H 5
CH 3
C
C
H 3C
O
C2H5
OH
OH
C
CH 3
CH 3
Cl
HBr
Br
H2O, Br2
C
C
HCl
C
C
HO
CH 3
C
C
C
NaEtO , EtO H
C
O
No Reaction
C
C
C
1, Cl2, hv
CO 2
2. tButO-, tButOH
3. KMnO4, H+, H2O
C
C
C
OH
Br
2 NBS
2 tButOK, tButOH
C
C
C
C
HBr, MCPBA
C
C
CH 3
C
C
CH 3
Br
O
IsoProK, IsoProH
C
C
C
C
C
C
C C
OH
Cl
C
C
C
KOH, T HF
C
C
C
C
C
C
NBS
C
C
C
C
MCPBA
C
C
C
Cl
HAc, Heat
HCl, MCPB A
CH 3
Cl
CH 3
Cl
C
C
CH 3
C
C
CH 3
1) KOH
2) H2SO4, Heat
C
C
Br
Cl
Br2, CH3OH
H3CO
Cl
KMn O4
H2O, H2SO4
O
C
C
C
O
C
OH
CH 3
Cl
C
C
KI, EtOH
C
C
CH 3
PBA
O
I
C
C
C
C
C
C
C
C
C
C
NaEtO , EtO H
C
C
C
CH 3
CH 3
C
C Br
C
C
OEt
C
C
C
1. Hg(OAc)2
2. C2H5OH
3. NaBH4
C
C
C
OC2H5
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.
Cl
KI, Ether
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
Cl
C
C
C
C
CH 3ONa, CH3OH
Cl
CH3
MeOH, Heat
Minor
Br
C
C
C
OH
HI
Major
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
OH
POCl3
C
C
C
Cl
EtOH
NaEtO
Major
Minor
CH3
C
C
C
MeOH
MeOK
SN1
SN2
Major
Br
CH3
HAc, Heat
SN1
O
H2SO4, H2O
E2
Minor
SN2
Minor
Cl
E1
E1
E2
Major
SN1
SN2
E1
E2
SN1
SN2
E1
E2
Cl
KOH, EtOH
C
Major
Minor
Cl
C
C
C
C
tButOH, Heat
SN1
Minor
SN2
E1
Major
E2
3) Please give the R,S and D, L designation for each of the following compounds,
COOH
CH3
H
H
C
CH3
H
C
COOH
Cl
C
OH
Cl
C
CH3
CH3
HOOC
C
CH3
HO
C
CH3
OH
Cl
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 3methyl butene.
CH3
C
C
C
H
H+
CH3
C
CH3
C
+
C
H
H
CH3
C
H
H
CH3
C
C
+
Cl -
CH3
C
H
CH3
C
C
H
Cl
5) Please give the complete mechanism of the halohydrin reaction caused by reacting
2-methyl butene with water and bromine.
CH3
H3C
C
H3C
C
CH3 Br
Br
Br+
CH3
H3C
C
C
H
OH-
CH3
H3C
H
C
C
CH3
OH H
6) Please draw the product of the Saytzeff elimination of 3R, 4S 3-chloro-4-methyl
hexane.
C
C
Cl
H
C
C
H
CH3
Cl
C2H5
C
CH3
C2H6
H
H
C
C
Cl
C2H5
C
Cl
H
C
C
H
CH3
CH3
C2H6
H
H
The chlroine and
the hydrogen must
opposite one another
C
Cl
H
C
C2H5 Rotate the
C2H5 back of the
molecule
H CH3
C2H5
H
CH3
C2H5
CH3
7) Please give the product of the Saytzeff elimination of HBr from the following
compound. Show your work.
H3C
C2H5 C
H
Br
C2H5
C H
Br
H
C2H5
H3C
C2H5
H3C
H
C2H5
H
H Br
C2H5
C2H5
C2H5
H
H3C
The bromine and
the hydrogen must
opposite one another
Rotate the
back of the
molecule
8) Please draw the complete mechanism of the E1 elimination of 2-methylcyclohexanol
using H3PO4 and heat.
H
OH
O
+ H2O
H
CH3
H
CH3
CH3
CH3
H+
H
H
H
CH3
Hydride
Shift
9) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3methyl pentene.
H
H
C
C
C
C
H
C
H
H
C
C
C
C
H
H
C
C
C
C
H
H
H+
C
H
H
H
C
H
C
H
C
C
C2H5OH
H
H+ +
H
H
C
C
C
C
C
H
H
O
C2H5
H
C
H
H
C
C
C
C
C
H
H
O
C2H5
C
H
10) Please give the complete mechanism of the anti-Markovinikov addition of HBr to
butene.
O
O
C
O
OH
C
O
+ OH
HBr
light
C
Br
+ C
C
C
Br
C
C
C
H2O + Br
Br
C
C
C
C
C
HBr
C
C
C
H
C
C
C + Br
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.
H
O
C
C
CH3
OH
O
H+
C
C
CH3
H2O
C
OH
C
CH3
O
H
H
C
C
CH3 + H+
O
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.
O
O
OH
C
Cl
HO
HCl
C
C
C
C
Cl
Energy
C
O
H
C
Cl
C
C
OH + HCl
O
C
H2 O + Cl
O
O
C
OH
Cl
C
C
HCl
C
C
C
C
C
C
Cl H
C
C
C
C + Cl
Reaction Coordinate
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.
H
+
OH
H
H
O
H
H
H
H
H
H
H
H
H
Energy
H
O
H
H
H
H
H
H
OH
H
H
H
+ H2 O
H
H
+ H+
H
Reaction Coordinate
16) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
H+
H
C
C
C
C
C
C
OH
C
H
C
C
C
C
C
O
C
C
C
C
O
C
H
Energy
H
C
C
C
C
+
C + H
C + C
C
OH
H
C
H
H
C
C
C
C
O
C
+ H+
Reaction Coordinate
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
100-X
= 6 (1º) x 1.0
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
100-X
= 6 (1º) x 1.0
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
100-X
= 12 (1º) x 1.0
8 (2º) x 3.5
X = 30% 1º and 70% 2º
Chem 240
Exam #2
Name___________________
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
1(12 )
Credit
2(28)
3(8)
4(26)
5(12)
6(14)
TOTAL
1) Please name or draw the structure of the following compounds.
H
CH3
H3C
C
Cl
H3C
C
Cl
Cl
OH
H
H
CH3
H
CH3
C2H5
H
Cl
D - 2 hydroxy propanoic acid
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
C
C
C
C
Br2, H2O
C
H
CH3
H
1) Br2, h
2) EtO-, EtOH
3) NBS
H2SO4, KBr
CH3
OH
C
C
C
EtOH, 
C
OH
C
C
C
P/I2
dil KMnO 4,
NaOH, H 2O
1) PBA
2) H2SO4, CH3OH
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.
OH
POCl 3
C
SN1
SN2
E1
E2
EtOH
NaEtO
SN1
SN2
E1
E2
MeOH
MeOK
SN1
SN2
E1
E2
SN1
SN2
E1
E2
C
C
Cl
CH3
C
C
C
Br
CH3
MeOH, Heat
Br
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.
COOH
Cl
H
H
C
Cl
H
C
COOH
Cl
C
H
H3C
C
Cl
HOOC
C
Cl
H
C
Cl
CH3
H
CH3
A
B
C
R,S ______
_______
________
D
________
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).
Chem 240
Exam #2
Name Answer Key
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
1(12 )
Credit
2(28)
3(8)
4(26)
5(12)
6(14)
TOTAL
1) Please name or draw the structure of the following compounds.
H
CH3
H3C
C
Cl
H3C
C
Cl
OH
H
Cl
H
Meso-2,3-dichlorobutane
CH3
H
CH3
C2H5
H
Cl
2R,33-2-chloro-3-methylpentane
R-chloroethanol
O
OH
C
H
C
OH
CH3
D - 2 hydroxy propanoic acid
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
Br
C
C
C
C
Br2, H2O
C
C
H
C
C
C
C
OH
(Br)
CH3
CH2(Br)
1) Br2, h
2) EtO-, EtOH
3) NBS
Three possible
products
(Br)
Br
H
H2SO4, KBr
CH3
CH3
OH
C
C
C
EtOH, 
No Reaction
C
I
OH
C
C
C
P/I2
dil KMnO 4,
NaOH, H 2O
C
C
H
C
H
OH OH
1) PBA
2) H2SO4, CH3OH
OH H
H
OCH3
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.
OH
POCl3
C
C
SN1
SN2
E1
E2
EtOH
NaEtO
SN1
SN2
E1
E2
MeOH
MeOK
SN1
SN2
E1
E2
C
Cl
CH3
C
C
C
Minor
Major
Br
CH3
MeOH, Heat
SN1
SN2
E1
Minor
Br
E2
Major
4) Please draw the complete mechanism of the acid catalyzed addition of ethanol to
propene. When you are finished draw the reaction diagram below.
H
C
C
H
HOC2H5
C
H
C
C
C
H
OC2H5
C
C
C
H
C
C
C
C
+
C
C
+ H+
H
H + OC2H5
C
C
C
+ C2H5OH
H
OC2H5
C
C
C + H+
H
H
C
C
C
H+
C
+
C
C
C2H5OH
H + OC2H5
H
OC2H5
C
C
C
C
C
C
+ H+
5) Please label the following compounds as R and S. Also, draw and label the missing
diastereomer/enantiomer.
COOH
Cl
H
H
C
Cl
H
C
COOH
Cl
C
H
H3C
C
Cl
COOH
HOOC
C
Cl
H
C
Cl
H
C
Cl
H
C
Cl
CH3
H
CH3
CH3
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
C
C
Br2, light
O
C
O3, (CH 3)2S
t-ButO-, t-ButOH
C
C
Br
C
C
C
C
C
C
C
C
C
C
Chem 240
Exam #2
Name___________________
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
1(20 )
Credit
2(32)
3(16)
4(12)
5(20)
TOTAL
1a) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3methyl 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.
Br H
H3C
C
C
H
H
C2H5
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.
OH
C
C
C
HCl, H2O
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
SN1
SN2
E1
E2
C
Cl
C
C
C
CH 3ONa, CH3OH
H
H2SO4, H3PO4
OH
Cl
tButOK, tButOH
C
C
C
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
Exam #2
Name__Answer Key _____
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
1(20 )
Credit
2(32)
3(16)
4(12)
5(20)
TOTAL
1a) Please draw the complete mechanism of the acid catalyzed addition of ethanol to 3methyl butene.
C
C
C
C
C
C
H+
C
H
C
+
C
C
C
Hydride
Shift
H
C
C
H
H
C
C
+
C
C2H5OH
C
C
C
C
H
H +OC2H5
H
C
H+ + C
C
C
C
H
H
OC2H5
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.
Less Stable Newman
Br
Br
H3C
C2H5
CH 3
H
H
C
C
H
H
C2H5
Br
H
The most stable Newman projection puts
the C2H5 and the CH3 opposite each other
which forces the product to be trans.
H
H
H
H3C
C2H5
C
C
H
H
H3C
H
CH 3
H C2H5
H
Br
C2H5
CH 3
C
H
H
Most Stable Newman
H
C
C2H5
Only Product Made
2) Please supply the product for each of the following reactions. If there is no reaction,
write “No Reaction.”
HBr, PBA
C
C
C
Br
C
C
C
OH
H2O, Br2
CH3
Br
CH3
1. Br2, light
C
C
C
C
2. tButOK, tButOH
3. O3, (CH3)2S
C
C
H
C
O
OCH3
1. PBA
2. H2SO4, CH3OH
CH3
OH CH3
Br
C
C
C
C
Acetic Acid, Heat
C
C
C
H
C
C
C
1. Hg(OAc)2
2. H2O
3. NaBH4
Br
Br OH
Br
OCH3
CH 3ONa, CH3OH
C
C
C
C
C
C
C
C
OH
HI, DMS O
CH3
No Reaction
O
CH2
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.
OH
C
C
C
HCl, H2O
Minor
Major
C
E2
E1
SN2
SN1
Cl
C
C
C
CH 3ONa, CH3OH
SN1
SN2
E1
E2
SN1
SN2
E1
E2
H
H2SO4, H3PO4
Major
Minor
OH
Cl
tButOK, tButOH
E2
E1
SN2
SN1
C
C
C
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.
C
C
C
C
C
C
H+
C
+
H
C
C
C
Hydride
Shift
H
C
C
H
H
C
+
C
C
Br-
C
C
C
H
H
Br
C
C
Br+
C
C
C
C
Br C
C
Br-
C
Br +
C
C
C
Br
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
C
C
C
C
CH4
C
C
1. Br2, h
2. t-ButO-, tButOH
3. O3, (CH3)2S
O
C
1. Br2, h
2. t-ButO-, tButOH
3. NBS
4. KOH, Ether
Br2, h
1. Br2, h
2. KOH, Ether
3. Na(s)
C
C
C
C
C
C
C
C
OH
Br
C
CH3O-
C
O
C