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Section 2c CHEM 222 Coursepack p. 211-248

Section 2c CHEM 222 Coursepack p. 211-248. Alcohol Synthesis. Organolithium and Grignard reagents deliver alkyl anion to C  O Acidic workup provides the alcohol. Alcohol Oxidation to Carbonyl. Oxidation of 1° alcohols makes aldehydes Oxidation of 2° alcohols makes ketones

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Section 2c CHEM 222 Coursepack p. 211-248

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  1. Section 2c CHEM 222 Coursepack p. 211-248

  2. Alcohol Synthesis • Organolithium and Grignard reagents deliver alkyl anion to C  O • Acidic workup provides the alcohol

  3. Alcohol Oxidation to Carbonyl • Oxidation of 1° alcohols makes aldehydes • Oxidation of 2° alcohols makes ketones • 3° Alcohols cannot be oxidized!

  4. Oxidation Reagents • Chromium trioxide (CrO3) in pyridine • Sodium chromate (Na2CrO4) or sodium dichromate (Na2CrO7) in H2SO4 (Jones Oxidation) • MnO2 is effective at making aldehydes • HNO3 and KMnO4 good for making carboxylic acids • DMSO and oxalyl chloride, (COCl)2, good at generating aldehydes (Swern Oxidation)

  5. Oxidation Examples

  6. List the reagents in the correct order to form compound A, from compound B. (Not all reagents needed) 1) PCC 2) HO-(CH2)2-OH /trace H3O+ 3) SOCl2 4) H3O+ 5) ClCOCH2CH2CH3 6) MgBr-(CH2)2-CH3/diethylether 7) Na2Cr2O7/H2SO4

  7. The following methods are all acceptable methods of forming ketones EXCEPT: A) Oxidation of secondary alcohol B) Reduction of carboxylic acid C) Ozonolysis of tetrasubstituted alkene D) Friedel crafts acylation E) Both B and C

  8. Which reagent would cause 1-butanol to be oxidized to butanal? A) PCC B) Na2Cr2O7, H2SO4 C) O3 D) LiAlH4

  9. Organometallic Reagents (cont.) • The Mg atom in a Grignard reagent is a strongly Lewis acidic site. It is usually stabilized by an ether solvent: • The formation of a Grignard reagent involves a radical mechanism: 9

  10. Organometallic Reagents (cont.) • The C atom attached to the metal in Grignard reagents and organolithium reagents has a lot of negative charge on it. It is a strong Brønsted base and can deprotonate water: 10

  11. Organometallic Reagents (cont.) • This reaction can be used to label specific sites with deuterium:

  12. Which solvent would not be appropriate to prepare a Grignard reagent in? A) CH3OH B) Et2O (ether) C) H2O D) Both A and C

  13. Organometallic Reagents • Organometallic reactions are irreversible • Organocuprates (R2CuLi) good reagents to displace halides • Organocuprates made from organolithium compounds and copper iodide

  14. Example of R2CuLi Reaction

  15. Solvents in Organic Chemistry • Solvents can play a key role in the properties of the solutes dissolved in them. The stronger solvent-solute interaction for methoxide versus t-butoxide is a reason that the latter is a stronger base: 15

  16. Solvents in Organic Chemistry (cont.) • A variety of polar solvents are commonly used in organic chemistry. They are classified as polar protic if they can engage in hydrogen bonding and polar aprotic if they cannot.

  17. Solvents in Organic Chemistry (cont.) • The saying “like dissolves like” reminds us that polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes. 17

  18. Solvents in Organic Chemistry (cont.) 18

  19. Solvents in Organic Chemistry (cont.) • Consider possible intermolecular interactions, i.e., between a polar solvent and an ionic compound: • Stronger interactions lead to better solubility!

  20. Solvents in Organic Chemistry (cont.) • A polar solvent can also dissolve polar organic compounds if there are strong enough intermolecular interactions between solvent and solute, like hydrogen bonding: 20

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