1 / 27

54c) Fill in the blanks.

54c) Fill in the blanks. 1. 2. 3. f). 2. 1. 3. 1. 2. j). 4. 3. 1. 2. k). 4. 5. 3. 1. 2. 55d). 3. 4. 1. 2. f). 3. 4. 5. j). 1. 2. 3. 4. 1. 2. k). 3. 4. 5. Oxidation and Reduction. Oxidation of Alcohols.

sun
Télécharger la présentation

54c) Fill in the blanks.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 54c) Fill in the blanks. 1 2 3

  2. f) 2 1 3

  3. 1 2 j) 4 3

  4. 1 2 k) 4 5 3

  5. 1 2 55d) 3 4

  6. 1 2 f) 3 4 5

  7. j) 1 2 3 4

  8. 1 2 k) 3 4 5

  9. Oxidation and Reduction Oxidation of Alcohols • Alcohols are oxidized to a variety of carbonyl compounds.

  10. Oxidation and Reduction Oxidation of Alcohols • Recall that the oxidation of alcohols to carbonyl compounds is typically carried out with Cr6+ oxidants, which are reduced to Cr3+ products. • CrO3, Na2Cr2O7, and K2Cr2O7 are strong, nonselective oxidants used in aqueous acid (H2SO4 + H2O). • PCC is soluble in CH2Cl2 (dichloromethane) and can be used without strong acid present, making it a more selective, milder oxidant.

  11. Oxidation and Reduction Oxidation of 2° Alcohols • Any of the Cr6+ oxidants effectively oxidize 2° alcohols to ketones.

  12. Oxidation and Reduction Oxidation of 1° Alcohols • 1° Alcohols are oxidized to either aldehydes or carboxylic acids, depending on the reagent.

  13. Oxidation and Reduction Oxidation of 1° Alcohols

  14. 2 58a) 1 4 3 5

  15. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • A single elimination reaction produces a  bond of an alkene. Two consecutive elimination reactions produce two  bonds of an alkyne.

  16. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • Two elimination reactions are needed to remove two moles of HX from a dihalide substrate. • Two different starting materials can be used—a vicinal dihalide or a geminal dihalide.

  17. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • Stronger bases are needed to synthesize alkynes by dehydrohalogenation than are needed to synthesize alkenes. • The typical base used is ¯NH2 (amide), used as the sodium salt of NaNH2. KOC(CH3)3 can also be used with DMSO as solvent.

  18. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis • The reason that stronger bases are needed for this dehydrohalogenation is that the transition state for the second elimination reaction includes partial cleavage of the C—H bond. In this case however, the carbon atom is sp2 hybridized and sp2 hybridized C—H bonds are stronger than sp3 hybridized C—H bonds. As a result, a stronger base is needed to cleave this bond.

  19. Alkyl Halides and Elimination Reactions E2 Reactions and Alkyne Synthesis Figure 8.9 Example of dehydrohalogenation of dihalides to afford alkynes

  20. b) 1 2

  21. Alkynes Introduction to Alkyne Reactions—Acetylide anions • Because sp hybridized C—H bonds are more acidic than sp2 and sp3 hybridized C—H bonds, terminal alkynes are readily deprotonated with strong base in a BrØnsted-Lowry acid-base reaction. The resulting ion is called the acetylide ion.

  22. Alkynes Reactions of Acetylide Anions • Acetylide anions react with unhindered alkyl halides to yield products of nucleophilic substitution. • Because acetylides are strong nucleophiles, the mechanism of substitution is SN2, and thus the reaction is fastest with CH3X and 10 alkyl halides.

  23. Alkynes Reactions of Acetylide Anions • Steric hindrance around the leaving group causes 2° and 3 ° alkyl halides to undergo elimination by an E2 mechanism, as shown with 2-bromo-2-methylpropane. • Thus, nucleophilic substitution with acetylide anions forms new carbon-carbon bonds in high yield only with unhindered CH3X and 1° alkyl halides.

  24. Alkynes Reactions of Acetylide Anions • Acetylide anions are strong nucleophiles that open epoxide rings by an SN2 mechanism. • Backside attack occurs at the less substituted end of the epoxide.

  25. 1 2 h) 4 3 5 6

More Related