Oxidation and Reduction Summary: Terms that Describe Reaction Selectivity

A regioselective reaction forms predominantly or exclusively one constitutional isomer

A stereoselective reaction forms predominantly or exclusively one stereoisomer

An enantioselective reaction forms predominantly or exclusively one enantiomer

Definitions of Oxidation and Reduction

Oxidation reactions result in:

an increase in the number of C—Z bonds, or

a decrease in the number of C—H bonds

Reduction reactions result in:

a decrease in the number of C—Z bonds, or

an increase in the number of C—H bonds

Reduction Reactions

Oxidation Reactions

Problem 12.1

Classify each reaction as oxidation, reduction, or neither.

a)

b)

c)

d)

Problem 12.2 What alkane is formed when each alkene is treated with H2 and a Pd catalyst?

a)

b)

c)

Problem 12.3 Draw all alkenes that react with one equivalent of H2 in the presence of a

palladium catalyst to form each alkane. Consider constitutional isomers only.

a)

b)

c)

Problem 12.4 Which alkene in each pair has the larger heat of hydrogenation?

a)

b)

Problem 12.5 Explain why heats of hydrogenation cannot be used to determine the relative

stability of 2-methyl-2-pentene and 3-methyl-1-pentene.

Problem 12.6 Given that syn addition of H2 occurs from both sides of a trigonal planar double

bond, draw all stereoisomers formed when each alkene is treated with H2.

a)

b)

c)

Problem 12.7 Complete the missing information for compounds A, B, and C, each subjected to

hydrogenation. The number of rings and π bonds refers to the reactant (A, B, or C) prior to

hydrogenation.

Problem 12.11

a) Draw the structure of a compound of molecular formula C6H10 that reacts with H2 in the

presence of Pd-C but does not react with H2 in the presence of Lindlar catalyst.

b) Draw the structure of a compound of molecular formula C6H10 that reacts with H2 when

either catalyst is present.

Problem 12.12What product is formed when CH3OCH2CH2C≡CCH2CH(CH3)2 is treated with

each reagent:

a) H2 (excess), Pd-C;

b) H2 (1 equiv), Lindlar catalyst;

c) H2 (excess), Lindlar catalyst;

d) Na, NH3?

Problem 12.15What epoxide is formed when each alkene is treated with mCPBA?

a) (CH3)2C=CH2

b) (CH3)2C=C(CH3)2

c)

Problem 12.16 Draw all stereoisomers formed when each alkene is treated with mCPBA.

a)

b)

c)

Problem 12.17 Draw the products formed when both cis- and trans-2-butene are treated with a

peroxyacid followed by −OH (in H2O). Explain how these reactions illustrate that anti

dihydroxylation is stereospecific.

Problem 12.18 Draw the products formed when both cis- and trans-2-butene are treated with

OsO4, followed by hydrolysis with NaHSO3 + H2O. Explain how these reactions illustrate that

syn dihydroxylation is stereospecific.

Problem 12.19 Draw the products formed when each alkene is treated with O3 followed by Zn,

H2O.

a) (CH3)2C=CHCH2CH2CH2CH3

b)

c)

Problem 12.20 What alkene yields each set of oxidative cleavage products?

a) (CH3)2C=O + (CH3CH2)2C=O

b)

c)

Problem 12.21 Draw the products formed when each diene is treated with O3 followed by

CH3SCH3.

a)

b)

c)

Problem 12.22 Draw the products formed when each alkyne is treated with O3 followed by H2O.

a) CH3CH2—C≡C—CH2CH2CH3

b)

c) CH≡C—CH2CH2—C≡C—CH3

Problem 12.23What alkyne (or diyne) yields each set of oxidative cleavage products?

a) CO2 + CH3(CH2)8CO2H

b) CH3CH2CH(CH3)CO2H only

c) CH3CH2CO2H, HO2CCH2CO2H, CH3CO2H

d) HO2C(CH2)14CO2H

Problem 12.24 Draw the organic products in each of the following reactions.

a)

b)

c)

d)

12.32 Label each reaction as oxidation, reduction, or neither.

a)

b) CH3CH2Br → CH2=CH2

c)

d)

12.33 Draw the organic products formed when each alkene is treated with H2, Pd-C. Indicate the

three-dimensional structure of all stereoisomers formed.

a)

b)

c)

d)

12.34 Match each alkene to its heat of hydrogenation.

Alkenes: 3-methyl-1-butene, 2-methyl-1-butene, 2-methyl-2-butene

∆H° (hydrogenation) kJ/mol: −119, −127, −112

12.35 How many rings and π bonds are contained in compounds A–C? Draw one

possible structure for each compound.

a) Compound A has molecular formula C5H8 and is hydrogenated to a compound

having molecular formula C5H10.

b) Compound B has molecular formula C10H16 and is hydrogenated to a compound

having molecular formula C10H18.

c) Compound C has molecular formula C8H8 and is hydrogenated to a compound

having molecular formula C8H16.

12.36 For alkenes A, B, and C:

a) Rank A, B, and C in order of increasing heat of hydrogenation;

b) rank A, B, and C in order of increasing rate of reaction with H2, Pd-C;

c) draw the products formed when each alkene is treated with ozone, followed by

Zn, H2O.

12.38 Draw the organic products formed when cyclopentene is treated with each reagent. With

some reagents, no reaction occurs.

a) H2 + Pd-C

b) H2 + Lindlar catalyst

c) Na, NH3

d) CH3CO3H

e) [1] CH3CO3H; [2] H2O, HO−

f) [1] OsO4 + NMO; [2] NaHSO3, H2O

g) KMnO4, H2O, HO−

h) [1] LiAlH4; [2] H2O

i) [1] O3; [2] CH3SCH3

j) NO

k) mCPBA

12.39 Draw the organic products formed when 4-octyne is treated with each reagent.

a) H2 (excess) + Pd-C

b) H2 + Lindlar catalyst

c) Na, NH3

d) [1] O3; [2] H2O

12.40 Draw the organic products formed when allylic alcohol A is treated with each reagent.

a) H2 + Pd-C

b) mCPBA

c) PCC

d) CrO3, H2SO4, H2O

12.41 Draw the organic products formed in each reaction.

a)

b)

c)

12.42 Draw the organic products formed in each reaction.

a)

b)

c)

d)

12.46 What alkene is needed to synthesize each 1,2-diol using [1] OsO4 followed by NaHSO3 in

H2O; or [2] CH3CO3H followed by –OH in H2O?

a)

b)

c)

12.49 Draw the products formed in each oxidative cleavage.

a)

b)

c)

d)

12.50 What alkene yields each set of products after treatment with O3 followed by

CH3SCH3?

a)

b)

c)

d)

12.51 Identify the starting material in each reaction.

a)

b)

12.52 What alkyne gives each set of products after treatment with O3 followed by H2O?

a) CH3CH2CH2CH2COOH and CO2

b) CH3CH2COOH and CH3CH2CH2COOH

c)

12.53 Draw the products formed when each naturally occurring compound is treated with

O3 followed by Zn, H2O.

a)

b)

c)

12.54 Identify compounds A, B, and C.

a) Compound A has molecular formula C8H12 and reacts with two equivalents of H2.

A gives HCOCH2CH2CHO as the only product of oxidative cleavage with O3

followed by CH3SCH3.

b) Compound B has molecular formula C6H10 and gives (CH3)2CHCH2CH2CH3

when treated with excess H2 in the presence of Pd. B reacts with NaNH2 and CH3I

to form compound C (molecular formula C7H12).

12.62 Devise a synthesis of each hydrocarbon from acetylene, and any other needed reagents.

a)

b)

c)

d)