alkene and alkyne reactions and synthesis dr. sheppard chem 2412 summer 2015 klein (2 nd ed.)...
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![Page 1: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/1.jpg)
ALKENE AND ALKYNE REACTIONSandSYNTHESIS
Dr. Sheppard
CHEM 2412
Summer 2015
Klein (2nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8, 9.9-9.12, 11.11, 10.4, 10.6-10.8, 10.5, 10.9, 10.3, 10.10, 9.13, 10.11, 12.1-12.6
![Page 2: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/2.jpg)
Outline• Nomenclature review• Preparation and reactions of alkenes (Ch. 9 and 11)• Preparation and reactions of alkynes (Ch. 10)• Synthesis (9.13, 10.11, Ch. 12)
![Page 3: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/3.jpg)
Alkene Nomenclature• Similar to alkanes; change infix from “-an-” to “-en-”
• For larger alkenes:
1. Parent is longest C chain containing both carbons of C=C
2. Number chain so C=C has lowest possible number• If the double bond is equidistant from both ends, start numbering at
end nearest the first substituent• Show location of C=C by first number• Alkenes with >1 C=C use “-adiene”, “-atriene”, etc. in place of “-ene”
and show location of all double bonds
3. Name and number substituents and write the full name
4. Determine stereochemistry (cis, trans, E, Z) if applicable
CH2 CH2 CH CH2CH3
ethene (ethylene) propene (propylene)
![Page 4: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/4.jpg)
ExamplesStructure Name
CH3 CH CH CH2
CH2 CH2 CH2
CH3
![Page 5: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/5.jpg)
Alkene substituents
Substituent Name
CH2═ methylene
CH2═CH─ vinyl
CH2═CH─CH2─ allyl
![Page 6: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/6.jpg)
Alkyne Nomenclature• Similar to alkenes; change infix from “-en-” to “-yn-”
• For larger alkynes:
1. Parent is longest C chain containing both carbons of C≡C
2. Number chain so C≡C has lowest possible number• Same rules as alkenes
3. Name and number substituents and write the full name
• Example
C CHCH3
ethyne (acetylene) propyne
CH CH
CH3 C C CH2 CH CH3
CH3
![Page 7: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/7.jpg)
Preparation of Alkenes: Review• Alkyl halide eliminates HX to form an alkene
• Reagent = base
• Alcohol eliminates water to form an alkene• Reagent = acid
![Page 8: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/8.jpg)
Reactions of Alkenes
I. Allylic halogenation
II. Electrophilic addition
III. Reduction
IV. Oxidation
V. Polymerization
![Page 9: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/9.jpg)
Reaction Charts• Help organize reaction details• Organize charts by reaction
type, starting material, product• See webpage for template• Example:
Reaction Type
Starting Material Reagent Regiochemistry/
stereochemistryRearrangement
possible? Product
Oxymercuration-demercuration
Alkene1. Hg(OAc)2, H2O
2. NaBH4 MarkovnikovAnti addition
no Alcohol
![Page 10: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/10.jpg)
I. Allylic Halogenation• Similar to radical halogenation of alkanes• Alkene react with molecular halogen in the presence of
heat or light• Alkyl halide is produced• Substitution of –X for –H at the allylic position
• Most stable radical intermediate• Stabilized by resonance
CH2 CH CH3
Br2
h
Allylic carbon
CH2 CH CH2
Br
+ HBr
![Page 11: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/11.jpg)
Allylic Halogenation• Another set of reagents:
• N-bromosuccinimide (NBS), hn• Bromination only (no chlorination)
• Product is a racemic mixture (if there is a stereocenter)
![Page 12: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/12.jpg)
Radical Stability
![Page 13: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/13.jpg)
• What is the major product of the reaction of 1-octene with NBS (in the presence of light)?
![Page 14: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/14.jpg)
• What is the major product of the reaction of 1-octene with NBS (in the presence of light)?
• Reaction occurs at less sterically hindered carbon and produces the more stable C=C
![Page 15: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/15.jpg)
• Another example:
• Which is the major product?
![Page 16: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/16.jpg)
• What is the major product of the following reaction?
CH2
NBS
h
![Page 17: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/17.jpg)
II. Electrophilic Addition• Most common reaction of alkenes
• Examples:
• Break p bond of alkene• Form new s bonds to each C of double bond• Alkene is nucleophile; reacts with electrophile (HX, H2O, etc.)
• Forms carbocation intermediate
C C + HX C C
H X
C C + H2O C C
H OH
![Page 18: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/18.jpg)
Electrophilic Addition• General mechanism:
• Step 1:
• Step 2:
• Which step is RDS?
C C + E C C
E
C C
E
+ Nu: C C
E Nu
![Page 19: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/19.jpg)
Hydrohalogenation• Addition of hydrogen halides
• HCl, HBr, HI
• Example: cis-3-hexane + HBr
![Page 20: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/20.jpg)
• What is the major product of the following reaction?
• Stereochemistry of product = racemic mixture• Carbocation intermediate is planar, sp2 hybridized
HBr
![Page 21: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/21.jpg)
• Regiochemistry of reaction• Which C gets the H? Which C gets the X?• Reaction is regioselective
![Page 22: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/22.jpg)
Regiochemistry of Electrophilic Addn.• Markovnikov’s Rule:
• In the addition of HX (or H2O) to an alkene, the H will add to the carbon with the greater number of H’s already bonded to it
• The X (or OH) attaches to the carbon with fewer H’s (the more substituted carbon)
• Product = Markovnikov product• Opposite product = anti-Markovnikov or non-Markovnikov
• Formed under specific conditions
![Page 23: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/23.jpg)
Markovnikov’s Rule
![Page 24: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/24.jpg)
Markovnikov’s Rule• Why is the Markovnikov product favored?• Look at reaction intermediate
• Carbocation
• Markovnikov addition forms the more stable R+
• 3º > 2º > 1º
• More stable carbocation forms faster, will react to give product
![Page 25: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/25.jpg)
Markovnikov’s Rule
![Page 26: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/26.jpg)
Mechanism for Hydrohalogenation
![Page 27: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/27.jpg)
Intermediate Structures• Two possible intermediates:
![Page 28: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/28.jpg)
• Draw and name the major product of the following reaction.
HBrCH3 CH2 CH
CH3
CH CH2
![Page 29: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/29.jpg)
• Draw and name the major product of the following reaction.
• Expected product =
• Actual product =
• What happened?
HBrCH3 CH2 CH
CH3
CH CH2
CH3 CH2 CH
CH3
CH CH3
Br
2-bromo-3-methylpentane
CH3 CH2 C
CH3
CH2 CH3
Br
3-bromo-3-methylpentane
![Page 30: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/30.jpg)
Carbocation Rearrangement• Carbocation intermediates can rearrange to form a more
stable carbocation structure• Hydride shift = H:- moves from C adjacent to carbocation
CH3 CH2 C
CH3
CH CH3
H
CH3 CH2 C
CH3
CH2 CH3
CH3 CH2 C
CH3
CH2 CH3
Br
3-bromo-3-methylpentane
Br
CH3 CH2 CH
CH3
CH CH2
H Br
hydride shif t
![Page 31: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/31.jpg)
Carbocation Rearrangement• Alkyl groups can also shift
• Typically methyl or phenyl
(Major product)
![Page 32: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/32.jpg)
Anti-Markovnikov Addition of HBr• In the presence of peroxides
• H2O2 or R2O2
• Free radical mechanism• Only HBr, not HCl or HI
• If product has a stereocenter, a racemic mixture is produced
HBrCH3 C
CH3
CH CH3 CH3 C
CH3
CH2 CH3
Br
HBrCH3 C
CH3
CH CH3 CH3 CH
CH3
CH CH3peroxides
Br
(Markovnikov)
(anti-Markovnikov)
![Page 33: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/33.jpg)
Mechanism
![Page 34: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/34.jpg)
Stability of Intermediate• In both Markovnikov and anti-Markovnikov reactions, the
most stable intermediate is formed
![Page 35: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/35.jpg)
Hydration• Addition of water• Three methods:
A. Acid-catalyzed hydration
B. Oxymercuration-demercuration
C. Hydroboration-oxidation
![Page 36: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/36.jpg)
A. Acid-catalyzed hydration
• Regiochemistry = Markovnikov• Stereochemistry = racemic mixture• Acid catalyst typically H2SO4 or H3PO4 (or just H3O+)
• Carbocation intermediate, so rearrangement can occur• Example:
CH CH2R CH CH3R
OH
H2O
H+
![Page 37: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/37.jpg)
Mechanism
![Page 38: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/38.jpg)
• Draw the major product of the following reaction.
H2O
H2SO4
![Page 39: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/39.jpg)
B. Oxymercuration-demercuration• Step 1: Alkene reacts with mercuric acetate• Step 2: Reduction with sodium borohydride
• Regiochemistry = Markovnikov• Anti addition of OH and H (add on opposite sides of C=C)• No rearrangements• Milder conditions than H3O+
• Electrophile is +HgOAc• Formed by dissociation of AcO-Hg-OAc
• Intermediate is bridged mercurinium ion
CH CH2R CH CH2R
OH
Hg(OAc)2
H2O
HgOAc
NaBH4CH CH2R
OH
H
![Page 40: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/40.jpg)
Oxymercuration-demercuration• Predict the products:
1. Hg(OAc)2, H2O
2. NaBH4
![Page 41: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/41.jpg)
Oxymercuration-demercuration• Oxymercuration mechanism:
• Demercuration mechanism: radical
![Page 42: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/42.jpg)
Oxymercuration-demercuration
![Page 43: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/43.jpg)
• Draw the major product for each of the following reactions.
1. Hg(OAc)2, H2O
2. NaBH4
CH3
1. Hg(OAc)2, H2O
2. NaBH4
CH3
CH3
![Page 44: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/44.jpg)
C. Hydroboration-oxidation
• Anti-Markovnikov product• Syn addition of H and OH (add on same side of C=C)• No rearrangements• THF stabilize highly reactive BH3
![Page 45: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/45.jpg)
Hydroboration-oxidation• Mechanism of first step:
• BH2 on the C with more H’s because less steric hindrance• Leads to anti-Markovnikov product
• Second step: H2O2/NaOH replace –BH2 with –OH • Complicated mechanism• Keep same stereochemistry (syn)
CH CH2R CH CH2R
BH2H BH2 H
CH CH2R
BH2H
H2O2
NaOHCH CH2R
OHH
![Page 46: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/46.jpg)
• Draw the major product of the following reactions.
1. BH3 THF
2. H2O2, NaOH
CH3
1. BH3 THF
2. H2O2, NaOH
![Page 47: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/47.jpg)
• Draw the major product formed when the following alkene undergoes (a) acid-catalyzed hydration, (b) oxymercuration-demercuration, and (c) hydroboration-oxidation.
CH3 CH CH CH2
CH3
![Page 48: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/48.jpg)
Halogenation
• Addition of halogens• X2 = Br2 or Cl2 (F2 too reactive, I2 unreactive)
• Solvent = inert, nonaqueous• Stereochemistry = anti addition• Product = a vicinal dihalide
• Two X atoms on adjacent carbons
• Example:
CH CH2R + X2
r.t.
CH2Cl2(CHCl3, CCl4)
CH CH2R
X
X
![Page 49: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/49.jpg)
Mechanism
C C Br Br+
![Page 50: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/50.jpg)
Addition of Halogens
![Page 51: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/51.jpg)
• Draw the major product of the following reaction.
Br2
CCl4
CH3
![Page 52: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/52.jpg)
Halohydrin formation
• Addition of halogens in the presence of water• Stereochemistry: X and OH add anti• Regiochemistry: X adds to the less substituted carbon
OH adds to the more substituted carbon• Mechanism the same as addition of X2, except H2O is the
nucleophile in the second step
![Page 53: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/53.jpg)
Mechanism
![Page 54: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/54.jpg)
Mechanism• Water attacks the carbon with the largest d+
• Results in OH on more substituted carbon
• Example:
C CH2R
R
Br
C CH2R
R
Br
not C CH2R
R
Br
![Page 55: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/55.jpg)
• Draw the major product of the following reaction.
Br2
H2O
CH3
![Page 56: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/56.jpg)
Oxidation and Reduction• What is oxidation?• What is reduction?
• Classify these reactions as oxidation or reduction:
• CH3─CH═CH2 → CH3─CH2─CH3
• CH3─CH2─OH → CH3─CO2H
![Page 57: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/57.jpg)
III. Reduction• Catalytic hydrogenation• Seen before with heat of hydrogenation (alkene stability)
• Catalyst = metal, usually Pd, Pt, or Ni• Reaction takes place on metal surface• Stereochemistry = syn (both H’s add to same side of C=C)
![Page 58: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/58.jpg)
Mechanism
![Page 59: ALKENE AND ALKYNE REACTIONS and SYNTHESIS Dr. Sheppard CHEM 2412 Summer 2015 Klein (2 nd ed.) sections 11.7, 9.1, 9.3, 11.10, 9.4-9.6, 9.8, 9.7, 14.8,](https://reader036.vdocuments.site/reader036/viewer/2022062802/56649e8a5503460f94b8f33f/html5/thumbnails/59.jpg)
Catalytic Hydrogenation
• This reduction does not work with C=O, C=N, or benzene except at very high P or T, or with a special catalyst
No enantiomer in this example because the product is achiral