Organic Chemistry I

CHEM 341: Organic Chemistry I at North Dakota State University

Final Exam - Study Guide

Reactions to know

Substitution of Alcohols R

+

OH

HX

R

+

X

HOH

SN1 Substitution H HCl

OH

- HOH

OH

Cl

Cl

3° carbocation best 2° carbocation ok

SN2 Substitution H HCl

OH

1° will not form carbocation R

OH

+

SOCl2

S

Cl

Cl

R

+

Cl

SO2

+

HCl

Cl

O Cl

- HOH

OH

O Cl

S

OH

O H

Cl

Cl

SN2 Substitution - will work with 1° and 2° alcohols, not 3° alcohols R

OH

+

PBr3

R

Br

H3PO3

Br

Br P

+

Br

Br Br

OH

Chem 341 Final Exam Study Guide!

P

O H

Br

page 1!

Br

spring 2012

Free Radical Halogenation

+

CH4

light

Cl2

CH3Cl

or heat

Initiation Cl Cl Propogation Cl

+

Cl

+

Cl

H

H

H H +

Cl

H

C H

H

H H

C

H +

Cl

Cl

H

H Termination H H

C

H

C

C

Cl

+

Cl

H H +

Cl

H

H

C

Cl

H

Elimination of Alcohols H R2C

OH

H+

CR2

CHR2 +

R2HC

HOH

E1 Elimination - proceeds through carbocation, 2° and 3° alcohols H OH

O

H3PO4

H

H

-H2O

H

H

H2PO4

E2 Elimination - 1° alcohols, requires anti-periplanar arrangement H OH

H3PO4

H

Chem 341 Final Exam Study Guide!

O H

H

H2PO4

page 2!

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Elimination of Halides H R2C

X

RO

CR2

R2C

+

CR2

HOR

E2 Elimination - 1°, 2° or 3° halides with strong base requires anti-periplanar arrangement Cl

K+ -OCH3

+

KCl

+

HOCH3

H E1 elimination can occur under neutral conditions only with 3° halides

Electrophilic Addition to Alkenes A A+

B-

B

or

A A

overall equivalent reagents

notes

H2O (H+ cat) BH3 then H2O2/OHHX H+

BHOHX-

Markovnikov

X2

X+

X-

bridged, anti addn

X2/H2O

X+

HO-

bridged, anti addn, Markovnikov

A+ H+ OH+

H3PO4

Markovnikov syn addn, anti-Markovnikov

OH H2O

H H2O 250°C Most stable intermediate Lower energy pathway

Chem 341 Final Exam Study Guide!

page 3!

H Markovnikov Addition

spring 2012

H

H3C C H3C

C

+

H

H3C

HBr

H

C

C

H3C

Br

H3C

H

C

H3C

H

Br

C

H

H

Markovnikov Addition

Most stable intermediate Lower energy pathway

Br

Br-Br

Br

A bromonium

Br Bromide can only come from the bottom and kick off the bromine on the top. This reaction forms the trans product selectively.

Br

Br

Br-Br

CH3

H2O

H2O

CH3

Br H

CH3

OH Markovnikov Addition even if there is no full carbocation

Hydroboration and Hydrogenation 1) BH3

H BH2

2) H2O2 / NaOH

H OH

anti-Markovnikov hydration syn addition H2 Pd/C

H H

Chem 341 Final Exam Study Guide!

page 4!

syn addition of H2

spring 2012

Reduction (Hydrogenation) Reactions H2

H

H

Pd/C

H

H

H2 Pd/C

H H2

H

H

Lindlar's Catalyst Pd(OAc)2 quinoline on CaCO3

Lindlar's Catalyst stops at alkene

Li

H

H trans alkene

NH3

H

Electrophilic Addition Reactions

cat. HgSO4 H2SO4 H 2O

Ketone O

Cl

HCl 1 equiv Br

Br2 1 equiv

HCl 1 equiv

Cl

Br2 1 equiv

Br Br

Br

Br

Cl

Br

Oxidation Reactions O3 then Zn/HOAc O

+ O

O O3 then

OH

Zn/H+

+

HO

O

O Cl

O

mCPBA

O

H

O

Chem 341 Final Exam Study Guide!

epoxidation

page 5!

spring 2012

Substitution Reactions δ+ H 3C

NaNH2

H

S

Cl

O

Cl

OH

O H

Br

S

Cl

Cl

Br

Br

Br

Br P

CH3

Na

Cl

O

δBr

Br Br

OH

O H

P

Tos-Cl pyridine

O S

OH

O

Cl

O

Tos

Tos-Cl

Elimination Reactions

Br

Br

KOH or NaNH2

Br or

Br

KOH or NaNH2

Br can be prepared by Br2 addition to an alkene

a vinyl bromide

You should know the mechanistic details of SN1, SN2, E1 and E2 mechanisms and what factors influence substitution vs elimination pathways. There are a number of different nucleophiles and electrophiles that participate. You should be familiar with those and be able to recognize what various reactants do.

Chem 341 Final Exam Study Guide!

page 6!

spring 2012

SN1

SN2

SUBSTRATE

3° >> 2° > 1°

1° > 2° >> 3°

NUCLEOPHILE

Weak OK

Strong

LEAVING GROUP

Stable Anions

Stable Anions

STEREOCHEM

Racemic

100% inversion

SOLVENT

Polar Protic

Polar Aprotic

R-X

SN1

E1

SN2

1°

X

X

favored

2°

ok

ok

favored in protic solvents no base

3°

N3

Br

Cl

CN

can compete witn SN1

favored with strong base

favored with strong or weak base

X

Strong Bases

SH

SR

OH

OR

NH2

bulkier is less nucleophilic

C CR

Chem 341 Final Exam Study Guide!

favored with strong base

favored with strong nucleophile

Good Nucleophiles

I

E2

page 7!

spring 2012

Preparation of Conjugated Dienes NBS peroxides

KOt-Bu t-BuOH

Br

Note that the allylic position is especially easy to form free radicals. Halides can be eliminated under base conditions to form conjugated dienes. Alcohols can be eliminated under acidic conditions. Reactions of Conjugated Dienes HBr H

H H

not formed Br

H

H

1,2-addition

Br

1,4-addition

Kinetic Control

0 °C

71%

29%

Thermodynamic Control

40 °C

15%

85%

Diels-Alder Reactions + CO2CH3

diene

cyclic transition state

dieneophile

CH3

CH3

+ CH3

CH3

O

CH3

dieneophile

exo transition state

CH3 opposite sides

O

endo product major

same side

endo transition state H

CH3

H

H H

opposite sides

O

Chem 341 Final Exam Study Guide!

H

CH3

H3C H

H

O

exo product minor

H

+

H

H

H

H3C

CO2CH3

CO2CH3

O

H

secondary orbital interaction with the carbonyl pi-bond lowers the energy for this transition state

page 8!

H3C

O

H

H

H H

same side

CH3

O

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Electrophilic Aromatic Substitution Br2 FeBr3

H

Br

Br NOT formed

H

Br

NEED TO KNOW MECHANISM Br H Br

Br2 FeBr3

H

Br

H

Br

Br

-HBr

Br Br2

Cl2 FeCl3

Br

Br

FeBr3

+

+ FeBr4

electrophile Cl Cl2

Cl

FeCl3

+

+ FeCl4

electrophile I2 CuI2

I

I2

I

CuI2

+

+ CuI3

electrophile HNO3 H2SO4

NO2

O HO N O

+

H2SO4

O N O electrophile

Fuming SO3 H2SO4

SO3H

O O S O

+

O O S OH

H2SO4

electrophile O R-Cl AlCl3

R

+

Cl O

Chem 341 Final Exam Study Guide!

page 9!

AlCl3

88%

spring 2012

Activating Electron Donating Groups

Deactivating Electron Withdrawing Groups

ortho, para directors OR

meta directors NO2 strongest (resonance)

strongest (resonance)

NR2

SO3H

SR

O

alkyl

weakest (inductive)

X weak

ortho, para directors but deactivating

R CN

Other Reactions of Benzene and Substituents

CH3

O C

KMnO4

O

O

C

KMnO4

OH

OH

O C

KMnO4

KMnO4

OH

No Reaction

O N Br NBS

Br

O O Ph

O O O

Ph

O H2

Zn(Hg)

Pd/C

H3O+ R

H2

Na / NH3

R

Pt 2000 psi

Chem 341 Final Exam Study Guide!

page 10!

spring 2012