Reaction Map- Reactions of Alcohols, Alkynes, and Alkenes PDF

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Summary

Elem Organic Chem...

Description

Typical Conditions

Notes [1°, 2° and 3° refers to primary, secondary, tertiary]

1

Free radical chlorination

Cl2, hγ

Not highly selective

2

Free radical bromination

Br 2, hγ

Highly selective for tertiary C–H Best for 2° and 3°, anti stereochemistry

Reaction

Reaction Map: Reactions of Alkanes, Alkyl Halides, Alkenes, Alkynes and Alcohols 56

Alkenyl halides X H R

51

Geminal Dihalides X

Vicinal Dihalides X X

R

R

X

H

50

54 49

23

22 21

53 48

24 20

R

X

X

R

47

Alkynes

29

Tetrahalides X X X X R R

37 38

15

30

43

19

31

44

8 60

7

58

18 68

67

61

66

62

O 4

Best for 3° alkyl halides; rearr possible w/ 2°

Thiol formation [SN2]

SH

10

Sulfide formation [SN2]

SR

11

Ester formation [SN2]

12

Azide formation [SN2]

N3

13

Nitrile formation [SN2]

CN

Disulfides R S S R

14

Alkyne formation [SN2] R C C

15

Addition of H-Cl To Alkenes

H–Cl

65

16

Addition of H-Br To Alkenes

H–Br

Markovnikov-selective; rearr. possible

Thiols

17

Addition of H-I To Alkenes

H–I

Markovnikov-selective; rearr. possible

18

Radical addition of H–Br to alkenes

HBr, hγ

anti-Markovnikov-selective; radical process

19

Hydrogenation of alkenes

Pd/C, H2

syn - selective

Alkene chlorination

Cl2, CCl4

anti- selective

Nu

8

3

63

6

64

5

7

R SH

1 2

Best for 3° alkyl halides; rearr possible w/ 2°

Ether Formation [SN1] "Solvolysis"

R

O Alkanes R–H

H 2O

ROH

SN2; best for 1° alkyl halides, 2° OK

Alkyl Halides

SN2; best for 1° alkyl halides, 2° OK

RCO 2

HO

"Carbonyls"

O

Competes with SN1 Best for 1° alkyl halides; 2° can compete w/ E2

9

R OH

17

HO

Alcohol Formation [SN1] "Solvolysis"

OH / H 2O

8

Ring opened products

Alcohols

16

polar solvent, heat

Alcohol Formation [SN2]

R OR

59

36

42

Elimination [E1]

5

Best for 1° alkyl halides; 2° can compete w/ E2

R

46 45

35

34

4

Ether Formation [SN2] RO /ROH ["Williamson Ether Synthesis"]

69

40

RO /ROH

7

26

Ethers

41 47

33 32

28

Elimination [E2]

6

R

27

Alkenes 39

R C C R

Epoxides O

R

25

52 Alkenyl dihalides

Cyclopropanes

OH

R

R

55

55

HO

3 57

Vicinal Diols

Halohydrins HO X

Name

9

10

R–X

in polar aprotic solvent

SN2; best for 1° alkyl halides, 2° OK SN2; best for 1° alkyl halides, 2° OK SN2; best for 1° alkyl halides, 2° OK Best for 1° alkyl halides; 2° can compete w/ E2 Markovnikov-selective; rearr. possible

14 Alkyl Sulfonates This "map" includes reactions typically covered in chapters covering: •Substitution and eliimination reactions of alkyl halides • Reactions of alkenes • Reactions of alkynes • Free-radical substitution of alkanes • Alcohols and thiols

11 13

12

It will be expanded as subsequent chapters are covered Please feel free to add comments or sugestions!

20 Sulfides ["Thioethers"] 21 R SR

10

R–OTs R–OMs

Alkene bromination

Br2, CCl4

anti- selective

22

Alkene iodination

I2, CCl4

anti- selective

23

Chlorohydrin formation

24

Bromohydrin formation

Cl 2, H 2O or NCS

Esters Nitriles

Azides

R C N

R N3

O R O R

Br 2, H 2O or NBS

25

Iodohydrin formation

26

Epoxidation of alkenes

Cl2, H 2O or NIS

27

Dihydroxylation of alkenes with OsO4

28

Dihydroxylation of alkenes (cold KMnO4)

RCO3H (e.g. m-CPBA) OsO4, KHSO3 (e.g. m-CPBA) KMnO 4, NaOH (cold, dilute)

anti- selective; Markovnikov selective, water is solvent. Alcohol solvent gives ether anti- selective; Markovnikov selective, water is solvent. Alcohol solvent gives ether anti- selective; Markovnikov selective, water is solvent. Alcohol solvent gives ether anti- selective; Markovnikov selective, water is solvent. Alcohol solvent gives ether syn- selective. KHSO3 helps remove Os syn- selective. Important to keep cold, otherwise oxidative cleavage occurs (see 31)

29

Ozonolysis (reductive workup)

O 3, then Zn/H+ or cleaves C=C to give two carbonyls. Alkenyl C-H bonds remain (CH3)2S

30

Ozonolysis (oxidative workup)

O 3, then H2O 2

cleaves C=C to give two carbonyls. Alkenyl C-H bonds oxidized to C–OH

31

Oxidative cleavage with KMnO 4

KMnO 4, acid, heat

cleaves C=C to give two carbonyls. Alkenyl C-H bonds oxidized to C–OH

32

Cyclopropanation (SimmonsSmith)

Cu/Zn, CH2I 2

syn-selective

33

Dichlorocyclopropanation

CHCl3, KOH

Formation of epoxides from halohydrins

NaH (strong base)

Opening of epoxides with aqueous acid

H 3O + (or H 2O/H2SO4 )

34

Acid-catalyzed ether formation

H 2SO4, ROH

Oxymercuration

Hg(OAc) 2, ROH, then NaBH 4

Markovnikov selective, alcohol is solvent

36

Oxymercuration

Hg(OAc) 2, H 2O, then NaBH 4

Markovnikov selective, water is solvent

Protonation of epoxide, then attack of H2O at most substituted carbon

58

Elimination of alcohols to form alkenes (acidic)

H 2SO4, heat

Follows Zaitsev's rule (most sub. alkene formed). Rearrangements can occur

POCl 3, pyridine

E2 reaction

Markovnikov selective, rearr. possible

37

Hydroboration

59

POCl 3 elimination of alcohols to alkenes

60

Acidic cleavage of ethers

BH 3, then NaOH, anti-Markovnikov selective, syn-selective H 2O 2

61

Conversion of alcohols to alkyl halides with PBr3

62

38

Acid-catalyzed hydration

H 2SO4, H 2O ("H3O +")

Markovnikov selective; rearr possible

39

Partial hydrogenation (Lindlar)

Lindlar, H 2

syn-selective

Partial hydrogenation (sodium reduction)

Na/NH 3

Internal SN2 reaction: inversion of configuration at carbon

syn-selective

35

40

56

57

HI, heat

Can proceed through SN2 or SN1 depending on type of alcohol

PBr 3

SN2 reaction. PCl3 can also be used to make alkyl chlorides

SOCl2 conversion of alcohols to alkyl chlorides

SOCl2

Usually taught as SN2. Pyridine can be used as base.

63

Alcohols to alkyl halides with HX

HCl, HBr, HI

Can go through SN1 or SN2 depending on type of alcohol

64

Tosylate and mesylate formation

TsCl or MsCl

Does not affect stereochemistry. Can use a base such as pyridine.

anti-selective

41

Alkyne hydroboration

BH3, then NaOH, anti-Markovnikov selective; tautomerization H 2O 2

42

Alkyne Oxymercuration

HgSO4, H 2O, H 2SO4

Markovnikov selective; tautomerization

65

Disulfide formation

I 2 (oxidant)

43

Alkyne Ozonolysis

O3

Carboxylic acids formed; terminal alkynes give CO2

66

Alcohol oxidation with PCC

PCC

44

Alkyne Ox. Cleavage [KMnO4]

KMnO 4, H +

same as ozonolysis

67

Alcohol oxidation with H 2CrO4

K 2Cr2O 7 + acid

1° alcohols to carboxylic acids, 2° alcohols to ketones.

45

Hydrogenation

Pd/C, H 2

Adds twice to alkynes

68

Dess Martin oxidation

Dess Martin Periodinane

1° alcohols to aldehydes; 2° alcohols to ketones

46

Alkyne double halogenation

Cl2, Br2, or I 2 (2 equiv)

Each individual reaction is anti-selective

69

Basic ring opening of epoxides

Grignards, –OH, LiAlH 4

Add to least substituted position of epoxides

47

Halogenation

Cl2, Br2, or I 2 (1 equiv)

anti-selective Markovnikov selective

48

Addition of H–Cl to Alkynes

H–Cl

49

Addition of H–Br to Alkynes

H–Br

Markovnikov selective

50

Addition of H–I to Alkynes

H–I

Markovnikov selective

51

Addition of H–X to haloalkenes

H–Cl, H–Br, or H–I

Markovnikov selective

52

Double addition of H–Cl to Alkynes

H–Cl [2 equiv]

Adds twice to alkyne; Markovnikov selective

53

Double addition of H–Br to Alkynes

H–Br [2 equiv]

Adds twice to alkyne; Markovnikov selective

54

Double addition of H–I to Alkynes

H–I [2 equiv]

Adds twice to alkyne; Markovnikov selective

55

Elimination of dihalides to give alkynes

NaNH2 [2 equiv]

vicinal or geminal dihalides; for terminal alkynes, 3 equiv NaNH2 required

Can use other oxidants but I2 is most common 1° alcohols to aldehydes; 2° alcohols to ketones...