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Carbonyl compounds

Carbonyl compounds. class. general formula. class. general formula. Ketones 酮. Esters 酯. Aldehydes 醛. Acid chlorides 酰卤. Carboxylic acids 羧酸. Amides 酰胺. Acid anhydride 酸酐. Chapter 10 Aldehydes and Ketones. Text 1: p 774-835 Text 2: p 311-348.

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Carbonyl compounds

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  1. Carbonyl compounds class general formula class general formula Ketones 酮 Esters 酯 Aldehydes 醛 Acid chlorides 酰卤 Carboxylic acids羧酸 Amides 酰胺 Acid anhydride 酸酐

  2. Chapter 10 Aldehydes and Ketones Text 1: p 774-835 Text 2: p 311-348

  3. Structure of the carbonyl group 1. C-sp2 hybridization 2. The bond angles is 120o. 3. It is a trigonal planar structure 4. The carbon-oxygen double bond consists of a sigma bond and a pi-bond Resonance structures

  4. Salicylaldehyde (from meadowsweet) 水杨醛 ([植]绣线菊) Benzaldehyde (from bitter almonds) 苯甲醛(苦杏仁) Vanillin (from vanilla beans) 香草醛 (香草豆) Piperonal (made from safrole; odor of heliotrope) 胡椒醛 由黄樟油精制备, [植] 向日葵气味 Cinnamaldehyde (from cinnamon) 肉桂醛 (3-苯基丙烯醛） ([植物]肉桂, 桂皮)

  5. Acetophenone 苯乙酮 乳香味 Muscone 麝香酮 Camphor 樟脑 Carvone 香芹酮 （-）薄荷味 （+）香菜味

  6. 10.1 Nomenclature of aldehydes and ketones IUPAC names common names aldehydes: alkane — alkanal ---ic acid—---aldehyde ketones: alkane — alkanone alkyl alkyl ketone Methanal 甲醛 formaldehyde Ethanal 乙醛 acetaldehyde Propanal 丙醛 propionaldehyde Butanal 丁醛 butyraldehyde (formic acid) (acetic acid) (propionic acid) (butyric acid)

  7. 3-bromobutanal 3-溴丁醛 β-bromobutyraldehyde 2-pentenal (pent-2-enal) 2-戊烯醛 benzenecarbaldehyde 苯甲醛 benzaldehyde cyclohexanecarbaldehyde 环己烷（基）甲醛 2-Naphthalenecarbaldehyde 2-萘甲醛

  8. 4-penten-2-one 4-戊烯-2-酮 2-propanone acetone 丙酮 dimethyl ketone 2-butanone (butan-2-one) 2-丁酮 methyl ethyl ketone 3-oxopentanal 3-氧代戊醛

  9. acetophenone (methyl phenyl ketone) 苯乙酮 benzophenone (diphenyl ketone) 二苯甲酮 2-formylbenzoic acid 2-甲酰基苯甲酸 4-acetylbenzenesulfonic acid 4-乙酰基苯磺酸

  10. 10.2 Physical properties of aldehydes and ketones Boiling point: alkane < ether < aldehyde< ketone < alcohol Solubility in water: acetone, ethanal are misible（混溶） with water (hydrogen bond) formaldehyde: 40% aqueous solution (formalin, 福尔马林) trioxane 三聚甲醛 paraldehyde 三聚乙醛

  11. ~1685 cm-1 ν: 1714 1745 1790 1815 cm-1 10.3 Spectroscopy of aldehydes and ketones IR C=O ~1710 cm-1 (O=)C-H 2720, 2820 cm-1 n-π*, weak, 280~300 nm; π -π*, strong, < 200 nm; C=C-C=O, >200 nm UV

  12. δ: 2.4 2.1 9~10 17 42 14 209 30 CH3CH2CH2COCH3 1H NMR: 1H NMR 13C NMR C=O: ~200 ppm, α-C: 30~40

  13. CH3CH2CH2COCH3 （1） 43 （2） Mclafferty rearrangement (麦氏重排) 86 58 71 MS γ-H is needed; m/e: even (偶数)

  14. 10.4 Synthesis of aldehydes and ketones 1. Aldehydes and ketones from oxidation of alcohols Oxidants: • K2Cr2O7 or Na2Cr2O7 / H2SO4 • CrO3/ H2SO4 • PCC (Pyridinium chlorochromate, 吡啶三氧化铬) • PDC (Pyridinium dichromate, 重铬酸吡啶盐)

  15. 2. Aldehydes and ketones from ozonolysis of alkenes

  16. + 3. Aldehydes and ketones from alkynes

  17. 4. Aromatic aldehydes and ketones from acylation of benzene derivatives Friedel-Crafts acylation Gatterman-Koch formylation (盖特曼-考赫甲酰化反应)

  18. 5. Synthesis of aldehydes and ketones using 1,3-dithiane 1,3- dithiane 1,3-二噻烷 （硫缩醛）

  19. 6. Synthesis of ketones from carboxylic acids

  20. 7. Synthesis of aldehydes and ketones from acid chlorides Not LiAlH4 Not RMgX

  21. 8. Synthesis of ketones from nitriles (腈 jing)

  22. 9. Other methods ……………………

  23. Assignments Problem 18-1, 7, 8, 9, 11

  24. acidity Nu 10.5 Reactions of aldehydes and ketones • Nucleophilic addition to the carbon-oxygen double bond • Reduction and oxidation of aldehydes and ketones • Reactions of α-H

  25. 1. Nucleophilic addition to the carbon-oxygen double bond Nucleophilic atom: C (carbon) O (oxygen) N (nitrogen) S (sulfur)

  26. alkynol (炔醇) 1). Carbon as nucleophilic atom (碳为亲核性原子) (1) organometallic reagents addition to C=O

  27. (2) The Wittig reaction: the addition of ylide (叶立德) (18-13) 魏悌希反应 The wittig reaction has proved to be a valuable method for synthesizing alkenes. Wittig was a co-winner of the Nobel prize for chemistry in 1979.

  28. Preparation of phosphorus ylides: 1° RX are prefered Mechanism: Methylenecyclohexane

  29. Problem 18-14 Trimethylphosphine is much less expensive than triphenylphosphine. Why is trimethylphosphine unsuitable for making most phosphorus ylides? Problem 18-15 Predict the products. What is the stereochemistry of the double bond in the product?

  30. (3) The addition of hydrogen cyanide (HCN) Cyanohydrins 腈醇, α-羟基腈

  31. Cyanohydrins are useful intermediates in organic synthesis. β-amino alcohol β-氨基醇 α-hydroxy acid α-羟基酸 α,β-unsaturated acid α,β-不饱和酸

  32. For example

  33. 2). Oxygen as nucleophilic atom (氧为亲核性原子) (1) The addition of water to aldehydes and ketones: formation of hydrates(水合物) Hydrate ( a gem-diol)同碳二醇 Catalysis: acid or base Reversible reaction 可逆反应 unstable How about the mechanisms ?

  34. (2) The addition of alcohols to aldehydes and ketones: Formation of Acetals(缩醛（酮）) hemiacetal 半缩醛(酮) acetal 缩醛(酮) Old use: acetal 缩醛 ketal 缩酮 IUPAC: acetal Catalysis: acid Reversible reaction 可逆反应

  35. Mechanism Hemiacetal 半缩醛(酮) SN1 acetal 缩醛(酮) Base (-OH) can not catalyze the acetal formation. Why?

  36. For example Cyclic acetals (环状缩酮)often have more favorable equilibrium constants than acyclic acetals.

  37. Example 1 Use of acetals as protecting groups （保护基）.

  38. Example 2

  39. Example 3

  40. 3). Nitrogen as nucleophilic atom(氮为亲核性原子) NH2—Hammonia 氨 NH2—R amine 胺 NH2—OH hydroxylamine 羟氨 NH2—NH2 hydrazine 肼 NH2—NHCONH2 semicarbazine 氨基脲

  41. (1) Formation of imines (亚胺) and enamine (烯胺) carbinolamine 醇胺 Catalysis: acid Reversible reaction 可逆反应 Imine 亚胺 Shiff base 西佛碱

  42. 2°amine 仲胺 enamine 烯胺 The pH value is crucial to imine formation. Why? Catalyst: Acid catalyzes the dehydration. Nu: the nucleophilicity of RNH2 can be weaken in strong acid conditions. Product: unstable in strong acid conditions.

  43. hydroxylamine 羟胺 oxime 肟 hydrazone 腙 hydrazine 肼 2,4-dinitrophenylhydrazine 2,4-二硝基苯肼 2,4-dinitrophenylhydrzone 2,4-二硝基苯腙 (2) Condensation with hydroxylamine (羟氨) and hydrazine (肼)

  44. semicarbazide 氨基脲 semicarbazone 缩氨基脲 肟、腙、缩氨基脲都是很好的结晶。有固定的熔点。 在酸性水溶液中加热分解为原来的醛酮。 可用来鉴别和提纯醛、酮。如实验室常用2，4-二硝基苯肼鉴别醛、酮。

  45. 4). Sulfur as nucleophilic atom硫为亲核原子 (1) Formation of thioacetals (硫缩醛和硫缩酮) Thiol硫醇 1，3-二噻烷

  46. (2) The addition of sodium bisulfite (NaHSO3) Sodium α-hydroxysulfonate α-羟基磺酸钠 产物为很好的结晶，不溶于饱和亚硫酸氢钠溶液。反应可逆，加酸可得原来的醛酮，故好可用于鉴别和提纯醛酮。

  47. 另外，用于制备腈醇，避免了直接使用HCN。

  48. Summary of the nucleophilic addition to C=O bond 1. Types of addition: Simple addition Addition-elimination To form C-C, C-O, C-S single bond To form C=C, C=N double bond 2. Factors affecting the reaction rate: Steric hindrance (空间位阻) Electronegative of the substituents（取代基电负性） Nucleophiles（亲核试剂强度） Catalyst (催化剂)

  49. Examples: (1) Reactivity: Aldehydes > ketones (2) Ability of forming hydrates: CH3CH2CHO HCHO Cl3CCHO K: 0.7 40 500 (3) Ability of forming cyanohydrins CH3CHO CH3COCH2CH3 (CH3)3CCOC(CH3)3 K: > 104 38 <=1 (4) The pH is crucial to imine formation

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