aldehydes and ketones ii oxidation and reduction synthesis
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Aldehydes and Ketones. II. Oxidation and Reduction; Synthesis

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Aldehydes and Ketones. II. Oxidation and Reduction; Synthesis. Chapter 17. Assignment for Chapter 17. Skip the following sections: Section 17.3 Sections 17.13 through 17.15 . Problem Assignment. In-Text Problems 17-1, 2, 3, 4 5 (NH 2 -NH 2 is misssing from the problem!!)

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assignment for chapter 17
Assignment for Chapter 17
  • Skip the following sections:
  • Section 17.3
  • Sections 17.13 through 17.15
problem assignment
Problem Assignment
  • In-Text Problems
    • 17-1, 2, 3, 4
    • 5 (NH2-NH2 is misssing from the problem!!)
    • 6 - 11 15, 17, 18
  • End-of-Chapter Problems
    • 1, 2, 3
oxidation and reduction an overview
Oxidation and reduction -- an overview
  • Oxidation: add O or remove H2
  • Reduction: remove O or add H2
  • Oxidation numbers are relatively useless for carbon!
reactions of sodium borohydride
Reactions of sodium borohydride
  • Aldehydes yield primary alcohols
  • Ketones yield secondary alcohols
  • Esters give no reaction!
  • Amides give no reaction!
keep water away from lithium aluminum hydride
Keep water away from lithium aluminum hydride!

LiOH + Al(OH)

+ 4 H2

+ 4 H

O

LiAlH

4

2

3

reactions of lithium aluminum hydride
Reactions of lithium aluminum hydride
  • Aldehydes give primary alcohols
  • Ketones give secondary alcohols
  • Esters give primary alcohols from the

carboxylic acid part of the ester

  • Amides give primary amines!!
sect 17 2 reduction of carbonyl groups with hydrogen
Sect. 17.2: Reduction of carbonyl groups with hydrogen
  • You really have to “pound” on carbonyl compounds to reduce them by using hydrogen under high pressure!
  • Aldehydes give primary alcohols
  • Ketones give secondary alcohols
  • Other carbonyl compounds, such as esters are virtually unreactive.
selective reduction of c c and c o bonds
Selective reduction of C=C and C=O bonds
  • Hydrogen/ Pt (low pressure): reduces C=C but not the C=O group
  • Sodium borohydride: reduces C=O but not the C=C group
sect 17 7 oxidations
Sect. 17.7: Oxidations

NOTE: A dehydrogenationis also a form of oxidation!

oxidation an overview
Oxidation: an overview

Mild oxidizers: CrO3 in pyridine

CrO3 in acetone

pyridinium chlorochromate (PCC)

Primary alcohols give aldehydes

Secondary alcohols give ketones

Strong oxidizers: K2Cr2O7 in acid

CrO3 in acid

KMnO4

Primary alcohols give carboxylic acids

Secondary alcohols give ketones

important
Important!!
  • Sarrett reaction: Primary alcohols get oxidized to aldehydes
  • Aldehydes are not further oxidized to carboxylic acids
important22
Important!!
  • PCC reactions: Primary alcohols get oxidized to aldehydes
  • Aldehydes are not further oxidized to carboxylic acids
sect 17 11 silver and copper oxidation of aldehydes
Sect. 17.11: Silver and Copper oxidation of aldehydes
  • Tollens: oxidation with silver ion yields a carboxylic acid; Ag+ is reduced to Ago (silver mirror)
  • Benedict’s: oxidation with copper ion yields a carboxylic acid; Cu2+ is reduced to Cu+ (Cu2O)
sect 17 12 reducing and non reducing sugars
Sect. 17.12: Reducing and non-reducing sugars
  • Carbohydrates that have hemi acetal structures are in equilibrium with a “free” aldehyde ---- reducing sugars
  • Carbohydrates that are in the acetal form, do not have free aldehyde --- non-reducing
  • Reducing sugar =positive Tollens/Benedicts
  • Non-reducing sugar = negative tests
sect 17 18 ketone synthesis using organometallic reagents
Sect. 17.18: Ketone Synthesis using Organometallic Reagents
  • Acid chlorides give ketones with lithium dialkyl cuprates
  • Acid chlorides give ketones with Grignard reagents, but only at low temperatures
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