OK - Organic 1 2011 6ed 09th Module Alkene and Alkyne Rxns

8/12/2019 OK - Organic 1 2011 6ed 09th Module Alkene and Alkyne Rxns

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ALKENES AND ALKYNES REACTIONS

A STUDENT SHOULD BE ABLE TO:

1. Given the starting materials and reaction conditions, predict the products of the followingreactions of alkenes and alkynes.

Regioselective Markovnikov addition of acids to alkenes and alkynes, including the acid-catalyzed addition of water (hydration). Rearrangement is possible in the additions toalkenes; tautomerization occurs in the hydration of alkynes.

Oxymercuration-Demercuration of alkenes (regioselective, Markovnikov)Hydroboration-Oxidation of alkenes (regioselective, anti-Markovnikov; stereospecific

syn ) and alkynes (involving tautomerization).Catalytic hydrogenation of alkenes (stereospecific syn )Addition of halogens and halohydrin formation via halonium ion (stereospecific anti ). In

the case of halohydrin formation, the reaction is also regioselective Markovnikov.Epoxidation of alkenes, and the hydrolysis of the resulting epoxides to glycols

(stereospecific anti addition).Glycol formation using either KMnO 4 (cold) or OsO 4 (stereospecific syn additions).Oxidative cleavage of alkenes and alkynes using ozonolysis; predict products as well as

identify starting alkenes from the products given.Stereospecific catalytic hydrogenation of alkynes to produce cis- alkenes and dissolvingmetal reduction of alkynes to produce trans- alkenes.

2. Using any of the above reactions, propose syntheses of compounds that can be madeusing alkenes or alkynes as starting materials or intermediates. As always, synthesis

problems may require any reaction that you have studied in the course so far.

3. Propose complete mechanisms, and predict and explain experimental results using yourknowledge of mechanisms. Important reactions include:

Markovnikov additions (which proceed by protonation of the alkene to give a carbocationwhich can rearrange).

Addition of halogens and halohydrin formation ( via formation of the halonium ion).Hydrolysis of epoxides (under acid conditions the oxygen is protonated first).

4. Understand the terms regioselectivity, ster eospecificity syn , anti , and identifycorresponding reactions. Pay attention to these issues in all of the reactions listed in 1.Be able to give examples of regioselective and stereospecific reactions.

Also distinguish the terms nucleophile and base and be able to identify and giveexamples of nucleophiles and electrophiles.


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To best prepare for this module, please work Chapter 9 and Chapter 10 Skill Builder problems inthe textbook.

A STUDENT WHO HAS MASTERED THE OBJECTIVES ON THE PREVIOUS PAGESHOULD BE ABLE TO SOLVE THE FOLLOWING PROBLEMS AND RELATED ONES:

1.1 Predict the major organic product or products of each of the following reactions.


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1.1

1.2 Predict the products of the following reaction.

1.3 Identify each of these unknowns from the information given.

a) O3 Zn

C6H12 ----> ------> H 2O

O | |

CH 3CH 2C-H+

O | |CH 3C-CH 3

b)

O3 Zn

C9H16 ----> ------> H 2O

O | |

CH 3CH 2C-HO +

2. Propose a synthesis of each of these compounds, from the given starting material and anyneeded inorganic reagent and/or solvent.

a)

O3 Zn

----> ------>H2 O


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2.

3. Propose a mechanism for each of the reactions shown.

OHa)

H 3O+ H 2O ---------->

OHO

b) (CH 3)2CHCH=CH 2 + HCl (CH 3)2CClCH 2CH 3

c) H 3O

+ H 2O ---------->

CH 2CH 3CH=CH 2 OH


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3. d) CH 3CH 2CH=CH 2 + Br 2 + I -----> CH 3CH 2CH CH 2 + Br

| |I Br

e)

CH 2 H 3O

+ H 2O ---------->

CH 3HO

f) H 3O (trace)------------------->

CH 2CH 3

4.1 Which of the following reactions is stereospecific? Explain.

4.2 Find and label nucleophiles, electrophiles and bases in the following reactions. Note thatall of the nucleophiles are Lewis bases, so put the label base only if the base does not

perform the nucleophilic function.


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4.2


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SOLUTIONS TO SAMPLE PROBLEMS:

1.1 Predict the major organic product or products of each of the following reactions.


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1.1

1.2 The products are:

a) O 3 Zn----> ------> H 2O

O

CHO

O O | | | |+ HCCH 2CH

1.3 The unknowns are:

a) CH 3CH 2CH=C(CH 3)2

b) CHCH 2CH 3

2. Propose a synthesis of each of these compounds, from the given starting material and anyneeded inorganic reagent and/or solvent.

OR this could be accomplished using BH 3-THF, then H 2O2, OH -, no RAR.


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2.

3. Mechanisms. Note that balanced equations are used throughout.

OHa)

H 3O+ H 2O ---------->

OHO

OH 2

+ H 3O ----->

OH

O + H 2OO H

O H + H 2O ----->

OH 2

OH+ H 2O ----->

OH

OH+ H 3O

b) (CH 3)2CHCH=CH 2 + HCl -----> (CH 3)2CClCH 2CH 3

(CH 3)2CHCH=CH 2 + HCl -----> (CH 3)2CHCHCH 3 + Cl

H |

(CH 3)2CCHCH 3 -----> (CH 3)2CCH 2CH 3

(CH 3)2CCH 2CH 3 + Cl -----> (CH 3)2CClCH 2CH 3


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3.

c) H 3O

+ H 2O ---------->CH=CH 2

OH

CH 2CH 3

----->

CH=CH 2

OH 2

+ H 3O ----->CHCH 3

+ H 2O

CHCH 3 CH 2CH 3

CH 2CH 3+ H 2O ----->

CH 2CH 3

OHOH 2

CH 2CH 3+ H 2O ----->

CH 2CH 3+ H 3O

H

d) CH 3CH 2CH=CH 2 + Br 2 + I -----> CH 3CH 2CH CH 2 + Br | |I Br

Br I

CH 3CH 2CH=CH 2 + BrBr ----- > CH 3CH 2CHCH 2 + Br

CH 3CH 2CHCH 2

Br

+ I CH 3CH 2CHCH 2----->

Br

e)

CH 2 H 3O

+ H 2O ---------->

CH 3HO

CH 2

+ H 2O

CH 3HO

+ H 3O ---------->

CH 3

+ H 2O

CH 3

------>

OH 2H3C

OH 2H3C

+ H 2O -- --- -> + H 3O


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3.

f) H 3O (trace)------------------->

CH 2 CH 3

+ H 2 O

CH 2

CH 3

+ H 3 O ----->

CH 3

+ H 2 O

CH 3

-- --- > + H 3 O

H

4.1. Reaction b) is stereospecific because the two hydrogens are added to the same face of thealkene in so called syn fashion. As a result, only the cis pair of enantiomers of the product forms.

No diastereomeric trans enantiomers will be found in the product mixture. Reaction a) is notstereospecific because the carbocation that forms and then rearranges is trigonal planar (note sp 2-hybridization of the carbon) and can be attacked from both sides. As a result, both possibleenantiomers will form in approximately equal amounts, so the product will be racemic.

4.2.


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Name _____________________________ Ninth Drill Test (Sample A)Organic Chemistry 2210DR Answer All Questions

1. Predict the major organic product or products the following reactions. Show correctstereochemisrtry where appropriate. Also label regioselective and stereospecificreactions.

2. Propose a synthesis of each of the following compounds from the given starting materialand any needed inorganic reagents or solvents.


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3. Propose a mechanism for each of the reactions shown.

4. Give the structure of the unknown from the information given.


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Name _________________________________________ Ninth Drill Test (Sample B)Organic Chemistry 2210DR Answer All Questions

1. Predict the major organic product of each of the following reactions.

2. Propose a synthesis of each. You may use any needed inorganic reagents and solvents.

a) (CH 3)3CCl from (CH 3)3COH

b) trans -1,2-cyclohexanediol from bromocyclohexane


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3. Propose a mechanism for each of the reactions shown. For problem a), first complete theequation by predicting the product.

4. Give the structure of the unknown from the information given.

OK - Organic 1 2011 6ed 09th Module Alkene and Alkyne Rxns

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