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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)


H H


H H

CCC


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


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


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+



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.



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


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





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



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___________________


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.



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 _____


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.



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

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