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Dr. Wolf's CHM 201 & 202 16-1 Chapter 16 Ethers, Epoxides, and Sulfides.

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Presentation on theme: "Dr. Wolf's CHM 201 & 202 16-1 Chapter 16 Ethers, Epoxides, and Sulfides."— Presentation transcript:

1 Dr. Wolf's CHM 201 & Chapter 16 Ethers, Epoxides, and Sulfides

2 Dr. Wolf's CHM 201 & Nomenclature of Ethers, Epoxides, and Sulfides

3 Dr. Wolf's CHM 201 & name as alkoxy derivatives of alkanes CH 3 OCH 2 CH 3 methoxyethane CH 3 CH 2 OCH 2 CH 3 ethoxyethane CH 3 CH 2 OCH 2 CH 2 CH 2 Cl 1-chloro-3-ethoxypropane Substitutive IUPAC Names of Ethers

4 Dr. Wolf's CHM 201 & name the groups attached to oxygen in alphabetical order as separate words; "ether" is last word CH 3 OCH 2 CH 3 ethyl methyl ether CH 3 CH 2 OCH 2 CH 3 diethyl ether CH 3 CH 2 OCH 2 CH 2 CH 2 Cl 3-chloropropyl ethyl ether Functional Class IUPAC Names of Ethers

5 Dr. Wolf's CHM 201 & name as alkylthio derivatives of alkanes CH 3 SCH 2 CH 3 methylthioethane CH 3 CH 2 SCH 2 CH 3 ethylthioethane (methylthio)cyclopentane Substitutive IUPAC Names of Sulfides SCH 3

6 Dr. Wolf's CHM 201 & cyclopentyl methyl sulfide analogous to ethers, but replace “ether” as last word in the name by “sulfide.” CH 3 SCH 2 CH 3 ethyl methyl sulfide CH 3 CH 2 SCH 2 CH 3 diethyl sulfide Functional Class IUPAC Names of Sulfides SCH 3

7 Dr. Wolf's CHM 201 & Oxirane (Ethylene oxide) Oxetane Oxolane (tetrahydrofuran) Oxane (tetrahydropyran) 1,4-Dioxane Names of Cyclic Ethers O O O OO O

8 Dr. Wolf's CHM 201 & Thiirane Thietane Thiolane Thiane Names of Cyclic Sulfides S S S S

9 Dr. Wolf's CHM 201 & bent geometry at oxygen analogous to water and alcohols, i.e. sp 3 hybidization Structure and Bonding in Ethers and Epoxides

10 Dr. Wolf's CHM 201 & ° H O H 105° 108.5° (CH 3 ) 3 C O C(CH 3 ) 3 132° H O CH 3 O Bond angles at oxygen are sensitive to steric effects

11 Dr. Wolf's CHM 201 & most stable conformation of diethyl ether resembles pentane An oxygen atom affects geometry in much the same way as a CH 2 group

12 Dr. Wolf's CHM 201 & most stable conformation of tetrahydropyran resembles cyclohexane An oxygen atom affects geometry in much the same way as a CH 2 group

13 Dr. Wolf's CHM 201 & Physical Properties of Ethers

14 Dr. Wolf's CHM 201 & boiling point 36°C 35°C 117°C Ethers resemble alkanes more than alcohols with respect to boiling point O OH Intermolecular hydrogen bonding possible in alcohols; not possible in alkanes or ethers.

15 Dr. Wolf's CHM 201 & solubility in water (g/100 mL) very small Ethers resemble alcohols more than alkanes with respect to solubility in water O OH Hydrogen bonding to water possible for ethers and alcohols; not possible for alkanes.

16 Dr. Wolf's CHM 201 & Crown Ethers

17 Dr. Wolf's CHM 201 & structure cyclic polyethers derived from repeating —OCH 2 CH 2 — units properties form stable complexes with metal ions applications synthetic reactions involving anions Crown Ethers

18 Dr. Wolf's CHM 201 & Crown-618-Crown-6 negative charge concentrated in cavity inside the molecule O OO O O O

19 Dr. Wolf's CHM 201 & Crown-618-Crown-6 negative charge concentrated in cavity inside the molecule O OO O O O

20 Dr. Wolf's CHM 201 & O OO O O O 18-Crown-618-Crown-6 forms stable Lewis acid/Lewis base complex with K + K+K+

21 Dr. Wolf's CHM 201 & O OO O O O 18-Crown-618-Crown-6 forms stable Lewis acid/Lewis base complex with K + K+K+

22 Dr. Wolf's CHM 201 & not soluble in benzene Ion-Complexing and Solubility K+F–K+F–K+F–K+F–

23 Dr. Wolf's CHM 201 & Ion-Complexing and Solubility O OO O O O K+F–K+F–K+F–K+F– add 18-crown-6 benzene

24 Dr. Wolf's CHM 201 & Ion-Complexing and Solubility O OO O O O O OO O O O K+K+ 18-crown-6 complex of K + dissolves in benzene benzene F – F –

25 Dr. Wolf's CHM 201 & Ion-Complexing and Solubility O OO O O O + F–F–F–F– O OO O O O K+K+ F – carried into benzene to preserve electroneutrality benzene

26 Dr. Wolf's CHM 201 & Application to organic synthesis Complexaton of K + by 18-crown-6 "solubilizes" salt in benzene Anion of salt is in a relatively unsolvated state in benzene (sometimes referred to as a "naked anion") Unsolvated anion is very reactive Only catalytic quantities of 18-crown-6 are needed

27 Dr. Wolf's CHM 201 & ExampleExample CH 3 (CH 2 ) 6 CH 2 Br KFKFKFKF 18-crown-6 benzene CH 3 (CH 2 ) 6 CH 2 F (92%)

28 Dr. Wolf's CHM 201 & Preparation of Ethers

29 Dr. Wolf's CHM 201 & Acid-Catalyzed Condensation of Alcohols* 2CH 3 CH 2 CH 2 CH 2 OH H 2 SO 4, 130°C CH 3 CH 2 CH 2 CH 2 OCH 2 CH 2 CH 2 CH 3 (60%) *Discussed earlier in Section 15.7

30 Dr. Wolf's CHM 201 & H+H+H+H+ (CH 3 ) 2 C=CH 2 + CH 3 OH (CH 3 ) 3 COCH 3 tert-Butyl methyl ether Addition of Alcohols to Alkenes

31 Dr. Wolf's CHM 201 & Think S N 2! primary alkyl halide + alkoxide nucleophile The Williamson Ether Synthesis

32 Dr. Wolf's CHM 201 & (71%) CH 3 CH 2 CH 2 CH 2 ONa + CH 3 CH 2 I CH 3 CH 2 CH 2 CH 2 OCH 2 CH 3 + NaI ExampleExample

33 Dr. Wolf's CHM 201 & CH 3 CHCH 3 ONa (84%) Another Example CH 2 Cl CH 2 OCHCH 3 CH 3

34 Dr. Wolf's CHM 201 & CH 3 CHCH 3 ONa (84%) Another Example CH 2 Cl CH 2 OCHCH 3 CH 3 Alkyl halide must be primary Alkoxide ion can be derived from primary, secondary, or tertiary alcohol

35 Dr. Wolf's CHM 201 & CH 2 OCHCH 3 CH 3 CH 2 Cl + CH 3 CHCH 3 ONa (84%) OH Na CH 2 OH HCl Origin of Reactants

36 Dr. Wolf's CHM 201 & CH 2 ONa + CH 3 CHCH 3 Br What happens if the alkyl halide is not primary?

37 Dr. Wolf's CHM 201 & CH 2 ONa + CH 3 CHCH 3 Br CH 2 OH + H2CH2CH2CH2C CHCH 3 Elimination by the E2 mechanism becomes the major reaction pathway. What happens if the alkyl halide is not primary?

38 Dr. Wolf's CHM 201 & Reactions of Ethers: A Review and a Preview

39 Dr. Wolf's CHM 201 & No reactions of ethers encountered to this point. Ethers are relatively unreactive. Their low level of reactivity is one reason why ethers are often used as solvents in chemical reactions. Ethers oxidize in air to form explosive hydroperoxides and peroxides. Summary of reactions of ethers

40 Dr. Wolf's CHM 201 & Acid-Catalyzed Cleavage of Ethers

41 Dr. Wolf's CHM 201 & CH 3 CHCH 2 CH 3 OCH 3 CH 3 Br HBr + (81%) CH 3 CHCH 2 CH 3 Br heat ExampleExample

42 Dr. Wolf's CHM 201 & CH 3 CH 3 CHCH 2 CH 3 O CH 3 CHCH 2 CH 3 O CH 3 H + H Br MechanismMechanism

43 Dr. Wolf's CHM 201 & CH 3 CH 3 Br CH 3 CHCH 2 CH 3 O CH 3 CHCH 2 CH 3 O H CH 3 CHCH 2 CH 3 O CH 3 H + Br– H Br MechanismMechanism

44 Dr. Wolf's CHM 201 & CH 3 CHCH 2 CH 3 Br CH 3 CH 3 Br HBr CH 3 CHCH 2 CH 3 O CH 3 CHCH 2 CH 3 O H CH 3 CHCH 2 CH 3 O CH 3 H + Br– H Br MechanismMechanism

45 Dr. Wolf's CHM 201 & HI 150°C ICH 2 CH 2 CH 2 CH 2 I (65%) O Cleavage of Cyclic Ethers

46 Dr. Wolf's CHM 201 & HI ICH 2 CH 2 CH 2 CH 2 I O H O + MechanismMechanism

47 Dr. Wolf's CHM 201 & HI ICH 2 CH 2 CH 2 CH 2 I O H O H O + I – I MechanismMechanism

48 Dr. Wolf's CHM 201 & HI ICH 2 CH 2 CH 2 CH 2 I O H O H O + I – I HI MechanismMechanism

49 Dr. Wolf's CHM 201 & Preparation of Epoxides: A Review and a Preview

50 Dr. Wolf's CHM 201 & Epoxides are prepared by two major methods. Both begin with alkenes. reaction of alkenes with peroxy acids (Section 6.19) conversion of alkenes to vicinal halohydrins, followed by treatment with base (Section 16.10) Preparation of Epoxides

51 Dr. Wolf's CHM 201 & Conversion of Vicinal Halohydrins to Epoxides

52 Dr. Wolf's CHM 201 & H OHOHOHOH Br H NaOH H2OH2OH2OH2O (81%) H H O ExampleExample

53 Dr. Wolf's CHM 201 & O Br H H –H OHOHOHOH Br H NaOH H2OH2OH2OH2O (81%) H H O ExampleExample via:

54 Dr. Wolf's CHM 201 & anti addition Epoxidation via Vicinal Halohydrins Br 2 H2OH2OH2OH2O OHOHOHOH Br

55 Dr. Wolf's CHM 201 & anti addition inversion Epoxidation via Vicinal Halohydrins Br 2 H2OH2OH2OH2O OHOHOHOH NaOH corresponds to overall syn addition of oxygen to the double bond Br O

56 Dr. Wolf's CHM 201 & anti addition inversion Epoxidation via Vicinal Halohydrins Br 2 H2OH2OH2OH2O OHOHOHOH NaOH corresponds to overall syn addition of oxygen to the double bond Br H H3CH3CH3CH3C CH 3 O H H H3CH3CH3CH3C H

57 Dr. Wolf's CHM 201 & anti addition inversion Epoxidation via Vicinal Halohydrins Br 2 H2OH2OH2OH2O OHOHOHOH NaOH corresponds to overall syn addition of oxygen to the double bond Br H H3CH3CH3CH3C CH 3 O H H H3CH3CH3CH3C H H H3CH3CH3CH3C H

58 Dr. Wolf's CHM 201 & Reactions of Epoxides: A Review and a Preview

59 Dr. Wolf's CHM 201 & All reactions involve nucleophilic attack at carbon and lead to opening of the ring. An example is the reaction of ethylene oxide with a Grignard reagent (discussed in Section 15.4 as a method for the synthesis of alcohols). Reactions of Epoxides

60 Dr. Wolf's CHM 201 & Reaction of Grignard Reagents with Epoxides CH 2 OMgX H3O+H3O+H3O+H3O+ H2CH2CH2CH2C O RMgXR RCH 2 CH 2 OH

61 Dr. Wolf's CHM 201 & H2CH2CH2CH2C CH 2 O + 1. diethyl ether 2. H 3 O + (71%) ExampleExample CH 2 MgCl CH 2 CH 2 CH 2 OH

62 Dr. Wolf's CHM 201 & Reactions of epoxides involve attack by a nucleophile and proceed with ring-opening. For ethylene oxide: Nu—H + Nu—CH 2 CH 2 O—H H2CH2CH2CH2C CH 2 O In general...

63 Dr. Wolf's CHM 201 & For epoxides where the two carbons of the ring are differently substituted: In general... CH 2 O CRH Nucleophiles attack here when the reaction is catalyzed by acids: Anionic nucleophiles attack here:

64 Dr. Wolf's CHM 201 & Nucleophilic Ring-Opening Reactions of Epoxides

65 Dr. Wolf's CHM 201 & NaOCH 2 CH 3 CH 3 CH 2 OH (50%) ExampleExample O H2CH2CH2CH2C CH 2 CH 3 CH 2 O CH 2 CH 2 OH

66 Dr. Wolf's CHM 201 & O H2CH2CH2CH2C CH 2 CH 3 CH 2 O –Mechanism

67 Dr. Wolf's CHM 201 & O H2CH2CH2CH2C CH 2 CH 3 CH 2 O –– CH 3 CH 2 O CH 2 CH 2 O Mechanism

68 Dr. Wolf's CHM 201 & O H2CH2CH2CH2C CH 2 CH 3 CH 2 O –– CH 3 CH 2 O CH 2 CH 2 O O CH 2 CH 3 H Mechanism

69 Dr. Wolf's CHM 201 & O H2CH2CH2CH2C CH 2 CH 3 CH 2 O –– CH 3 CH 2 O CH 2 CH 2 O CH 3 CH 2 O CH 2 CH 2 O H O CH 2 CH 3 – O CH 2 CH 3 H Mechanism

70 Dr. Wolf's CHM 201 & (99%) ExampleExample O H2CH2CH2CH2C CH 2 KSCH 2 CH 2 CH 2 CH 3 ethanol-water, 0°C CH 2 CH 2 OH CH 3 CH 2 CH 2 CH 2 S

71 Dr. Wolf's CHM 201 & StereochemistryStereochemistry Inversion of configuration at carbon being attacked by nucleophile Suggests S N 2-like transition state NaOCH 2 CH 3 CH 3 CH 2 OH O HHH OHOHOHOH H OCH 2 CH 3 (67%)

72 Dr. Wolf's CHM 201 & NH 3 H2OH2OH2OH2O (70%) R S R R StereochemistryStereochemistry H3CH3CH3CH3C CH 3 H3CH3CH3CH3C O H H H H OH H2NH2NH2NH2N Inversion of configuration at carbon being attacked by nucleophile Suggests S N 2-like transition state

73 Dr. Wolf's CHM 201 & NH 3 H2OH2OH2OH2O (70%) ++++ ---- R S R R StereochemistryStereochemistry H3CH3CH3CH3C CH 3 H3CH3CH3CH3C O H H H H OH H2NH2NH2NH2N H3NH3NH3NH3N O H3CH3CH3CH3C H H3CH3CH3CH3C H

74 Dr. Wolf's CHM 201 & NaOCH 3 CH 3 OH CH 3 CH CCH 3 CH 3 OHOHOHOH CH 3 O (53%) C C H H3CH3CH3CH3C CH 3 O consistent with S N 2-like transition state Anionic nucleophile attacks less-crowded carbon

75 Dr. Wolf's CHM 201 & Anionic nucleophile attacks less-crowded carbon 1. diethyl ether 2. H 3 O + MgBr + O H2CH2CH2CH2C CHCH 3 CH 2 CHCH 3 OHOHOHOH (60%)

76 Dr. Wolf's CHM 201 & (90%) Hydride attacks less-crowded carbon Lithium aluminum hydride reduces epoxides O H2CH2CH2CH2C CH(CH 2 ) 7 CH 3 1. LiAlH 4, diethyl ether 2. H 2 O OHOHOHOH H3CH3CH3CH3C CH(CH 2 ) 7 CH 3

77 Dr. Wolf's CHM 201 & Acid-Catalyzed Ring-Opening Reactions of Epoxides

78 Dr. Wolf's CHM 201 & ExampleExample O H2CH2CH2CH2C CH 2 CH 3 CH 2 OCH 2 CH 2 OH (87-92%) CH 3 CH 2 OCH 2 CH 2 OCH 2 CH 3 formed only on heating and/or longer reaction times CH 3 CH 2 OH H 2 SO 4, 25°C

79 Dr. Wolf's CHM 201 & ExampleExample O H2CH2CH2CH2C CH 2 HBr 10°C BrCH 2 CH 2 OH (87-92%) BrCH 2 CH 2 Br formed only on heating and/or longer reaction times

80 Dr. Wolf's CHM 201 & Mechanism O H2CH2CH2CH2C CH 2 + H Br – O H2CH2CH2CH2C CH 2 H Br

81 Dr. Wolf's CHM 201 & Mechanism O H2CH2CH2CH2C CH 2 + H O Br CH 2 CH 2 H Br – O H2CH2CH2CH2C CH 2 H Br

82 Dr. Wolf's CHM 201 & Figure 16.6 Acid-Catalyzed Hydrolysis of Ethylene Oxide O H2CH2CH2CH2C CH 2 + H O H2CH2CH2CH2C CH 2 O HHH + O H H Step 1

83 Dr. Wolf's CHM 201 & Figure 16.6 Acid-Catalyzed Hydrolysis of Ethylene Oxide O H2CH2CH2CH2C CH 2 O +HH H Step 2 + O O CH 2 CH 2 HH H

84 Dr. Wolf's CHM 201 & Figure 16.6 Acid-Catalyzed Hydrolysis of Ethylene Oxide O HH Step 3 + O O CH 2 CH 2 HH H O HH + H O O CH 2 CH 2 HH

85 Dr. Wolf's CHM 201 & Acid-Catalyzed Ring Opening of Epoxides nucleophile attacks more substituted carbon of protonated epoxide inversion of configuration at site of nucleophilic attack Characteristics:

86 Dr. Wolf's CHM 201 & CH 3 OH CH 3 CH CCH 3 CH 3 OHOHOHOH OCH 3 (76%) C H H3CH3CH3CH3C CH 3 O consistent with carbocation character at transition state Nucleophile attacks more-substituted carbon H 2 SO 4 C

87 Dr. Wolf's CHM 201 & b CH 3 OH CH 3 CH CCH 3 CH 3 OHOHOHOH OCH 3 (76%) C H H3CH3CH3CH3C CH 3 OHOHOHOH consistent with carbocation character at transition state Nucleophile attacks more-substituted carbon H 2 SO 4 C ++ ++ ++

88 Dr. Wolf's CHM 201 & StereochemistryStereochemistry Inversion of configuration at carbon being attacked by nucleophile (73%) HHO HBr H OHOHOHOH Br H

89 Dr. Wolf's CHM 201 & (57%) R S R R StereochemistryStereochemistry H3CH3CH3CH3C CH 3 H3CH3CH3CH3C O H H H H OH CH 3 O Inversion of configuration at carbon being attacked by nucleophile CH 3 OH H 2 SO 4

90 Dr. Wolf's CHM 201 & R S R R StereochemistryStereochemistry H3CH3CH3CH3C CH 3 H3CH3CH3CH3C O H H H H OH CH 3 O CH 3 OH H 2 SO 4 ++++ ++++ CH 3 O O H3CH3CH3CH3C H H3CH3CH3CH3C H H ++++ H

91 Dr. Wolf's CHM 201 & H2OH2OH2OH2O HClO 4 (80%) anti-Hydroxylation of Alkenes HH CH 3 COOH O HHO H OHOHOHOH OH H

92 Dr. Wolf's CHM 201 & Epoxides in Biological Processes

93 Dr. Wolf's CHM 201 & are common are involved in numerous biological processes Naturally Occurring Epoxides

94 Dr. Wolf's CHM 201 & enzyme-catalyzed oxygen transfer from O 2 to alkene enzymes are referred to as monooxygenases Biosynthesis of Epoxides + + C C ++ O2O2O2O2 H+H+H+H+ C C O NADH H2OH2OH2OH2O + NAD + enzyme

95 Dr. Wolf's CHM 201 & this reaction is an important step in the biosynthesis of cholesterol Example: biological epoxidation of squalene O 2, NADH monoxygenase O

96 Dr. Wolf's CHM 201 & Preparation of Sulfides

97 Dr. Wolf's CHM 201 & prepared by nucleophilic substitution (S N 2) Preparation of RSR' +R'XS R – R S R' CH 3 CHCH CH 2 Cl NaSCH 3 methanol CH 3 CHCH CH 2 SCH 3

98 Dr. Wolf's CHM 201 & Oxidation of Sulfides: Sulfoxides and Sulfones

99 Dr. Wolf's CHM 201 & either the sulfoxide or the sulfone can be isolated depending on the oxidizing agent and reaction conditions Oxidation of RSR' R S R' R S R' O –+ R S R' O – ++O – sulfidesulfoxidesulfone

100 Dr. Wolf's CHM 201 & ExampleExample SCH 3 NaIO 4 SCH 3 O –+ Sodium metaperiodate oxidizes sulfides to sulfoxides and no further. (91%) water

101 Dr. Wolf's CHM 201 & ExampleExample H2O2H2O2H2O2H2O2 1 equiv of H 2 O 2 or a peroxy acid gives a sulfoxide, 2 equiv give a sulfone (74-78%) (2 equiv) SCH CH 2 SCH O –++ CH 2 O –

102 Dr. Wolf's CHM 201 & Alkylation of Sulfides: Sulfonium Salts

103 Dr. Wolf's CHM 201 & product is a sulfonium salt Sulfides can act as nucleophiles + R" X S R R S R" R'R' + X–X–X–X–

104 Dr. Wolf's CHM 201 & ExampleExample CH 3 (CH 2 ) 10 CH 2 SCH 3 CH 3 I CH 3 (CH 2 ) 10 CH 2 SCH 3 CH 3 + I–I–I–I–

105 Dr. Wolf's CHM 201 & Spectroscopic Analysis of Ethers

106 Dr. Wolf's CHM 201 & C—O stretching: 1070 and 1150 cm -1 (strong) Infrared Spectroscopy

107 Dr. Wolf's CHM 201 & Wave number, cm -1 Figure 16.8 Infrared Spectrum of Dipropyl Ether C—O—C CH 3 CH 2 CH 2 OCH 2 CH 2 CH 3

108 Dr. Wolf's CHM 201 & H—C—O proton is deshielded by O; range is ca.  ppm. 1 H NMR CH 3 CH 2 CH 2 OCH 2 CH 2 CH 3  0.8 ppm  1.4 ppm  3.2 ppm

109 Dr. Wolf's CHM 201 & Chemical shift ( , ppm) CH 3 CH 2 CH 2 OCH 2 CH 2 CH 3

110 Dr. Wolf's CHM 201 & ppm Carbons of C—O—C appear in the range  ppm ppm 13 C NMR O

111 Dr. Wolf's CHM 201 & Simple ethers have their absorption maximum at about 185 nm and are transparent to ultraviolet radiation above about 220 nm. UV-VISUV-VIS

112 Dr. Wolf's CHM 201 & Molecular ion fragments to give oxygen-stabilized carbocation. m/z 102 CH 3 CH 2 O CHCH 2 CH 3 CH 3 CH 3 CH 2 O + CH CH 3 CH 3 CH 2 O + CHCH 2 CH 3 m/z 87 m/z 73 Mass Spectrometry +

113 End of Chapter 16


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