Lecture 15: Oxidation and Reduction of Carbonyls, Hydride Reagents, Organometallic Reagents

How to identify Oxidation vs Reduction?

Nox(product)-Nox(reactant)

+: oxidation

-: reduction

PCC

1° alcohol—> aldehyde (O=C2-H)

2° alcohol—> ketone (C=O)

Reagents: CrO3, HCl, Pyridine

Jones

1° alcohol—>carboxylic acid (O=C-OH)

2° alcohol—> ketone (C=O)

aldehyde—> carboxylic acid

Reagents: H2O, H2SO4, CrO3

Tollens

selectively converts aldehyde—> carboxylic acid

*think of TAC

Reagents: Ag2O, NH4OH, H2O

Why can PCC and Jones oxidize primary and secondary alcohols but NOT tertiary?

Because tertiary alcohols have no protons on the alpha carbons to the alcohol

Steps for PCC mechanism

1. Identify Nu and LG-E

2. SnAc part 1: Nu attacks E and break double bond

3. Acid base

4. SnAc part 2: LG leaves, regenerate double bond (E2)

Reagents to convert carboxylic acid to ester (O=C-O)

NaH, BrCH3

H2SO4, HOCH3

List the organometallic reagents

Grignard: R-MgBr

Organolithium: R-Li

Terminal Alkyne: R-C≡CNa)

What bonds do organometallic reagents form?

New C-C bonds

Organometallic reagents just add to which types of carboys?

Ketons and aldehydes

What bonds do hydride reagents form?

New C-H bonds

Name 2 types of hydride reagents

1. LiAlH4

2. NaBH4

What does LiAlH4 do in a rxn?

Less selective: will change ALL Oxygen—>OH

What does NaBH4 do in a rxn?

More selective, will change some Oxygen—>OH