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Aldehydes and Ketones Overview

ALDEHYDES AND KETONES

MAIN IDEA

  • Aldehydes and ketones are organic molecules defined by the presence of the carbonyl group.

    • Carbonyl Group: A carbon atom double-bonded to an oxygen atom.

    • Aldehyde: Carbonyl group is at the end of a carbon chain.

    • Ketone: Carbonyl group is in the middle of a carbon chain.

  • Both functional groups are reactive, capable of undergoing oxidation and reduction reactions, and reacting with alcohols.

SKILLS TO MASTER

  • Naming: Identify correct names for aldehydes and ketones.

  • Oxidation Products: Predict the product of aldehyde oxidation, including recognizing oxidizing reagents that can also oxidize alcohols.

  • Reduction Products: Predict the product of the reduction of an aldehyde or ketone.

  • Reaction Type Identification: Determine if a reaction is an oxidation or a reduction.

  • Aldehyde/Ketone-Alcohol Reactions: Anticipate the product of reactions between aldehydes or ketones and alcohols, including distinguishing products based on the number of alcohol molecules involved.

  • Identify Acetals/Hemiacetals: Determine whether a molecule is an acetal or a hemiacetal.

TERMINOLOGY

  • Acetal (ASS-i-tal)

  • Aldehyde (al-DUH-hide)

  • Carbonyl (car-buh-KNEEL)

  • Hemiacetal (hem-ee-ASS-i-tal)

  • Ketone (key-TONE)

  • Oxidation

  • Reduction

NAMING ALDEHYDES AND KETONES

Naming Overview

  • Both aldehydes and ketones contain a carbon-oxygen double bond functional group.

  • Identifying Longest Chain: Essential to include the carbon-oxygen double bond in the longest carbon chain.

    • Numbering begins from the end closest to the double bond.

  • Name branches or substituents following conventional naming rules.

Definitions of Aldehydes and Ketones

  • Aldehyde:

    • Characterized by a carbon-oxygen double bond attached to at least one hydrogen.

    • Suffix: “-al”

    • Example: To name an aldehyde, drop the final "e" and replace it with "-al."

  • Ketone:

    • Contains a carbon-oxygen double bond without any hydrogen atoms attached.

    • Typically has carbon atoms adjacent to the double bond.

    • Suffix: “-one”

    • Example: To name a ketone, drop the "e" from the molecule name and replace it with "-one."

Specific Examples of Aldehyde and Ketone Naming

  • Aldehyde Example:

    • 1-butanol

    • Four-carbon chain (butane), with the double bond on carbon 1.

  • Ketone Example:

    • 2-propanone

    • Three-carbon chain (propane) with the double bond on carbon 2.

  • Ketone with Bromine:

    • 3-bromo-2-pentanone

    • Five-carbon chain (pentane), indicating the bromine branch on carbon 3.

  • Cyclic Ketone Example:

    • Cyclopentanone

    • Refers to a cyclic structure with one carbon-oxygen double bond.

REDUCTION OF ALDEHYDES AND KETONES

Reaction Classification and Prediction

  • Classify reactions as oxidation or reduction and predict their products.

Key Concepts

Aldehyde Specifics

  • Confusion regarding the opposite side of the carbon-oxygen double bond can have either a carbon atom or hydrogen.

General Reduction Overview

  • Both aldehydes and ketones undergo reduction to form alcohols,

    • Aldehydes yield primary alcohols.

    • Ketones yield secondary alcohols.

OXIDATION REACTIONS OF ALDEHYDES

Definition and Process

  • Oxidation Reaction: Aldehydes convert to carboxylic acids by adding an oxygen atom.

  • Representation often includes oxidation denoted as capital "O" in square brackets above the reaction arrow.

Reagents for Oxidizing Aldehydes

  • Tollen's Reagent:

    • Common Name: Tollen's reagent.

    • Chemical Composition: Silver (I) oxide Ag2O and ammonium hydroxide NH4OH.

  • Potassium Dichromate:

    • Chemical Composition: K2Cr2O_7,

    • Functions also to oxidize alcohols in addition to aldehydes.

Examples of Aldehyde Oxidation Reactions

  • Example 1: Using both K2Cr2O7 and Tollen's reagent, the reaction involves similar mechanisms and products.

  • Example 2: Involves an aldehyde reacting with an alcohol using K2Cr2O7, resulting in alcohol oxidizing to a carboxylic acid.

  • Example 3: Understanding that ketones do not undergo oxidation and remain unaffected in reactions involving aldehydes.

REDUCTION REACTIONS OF ALDEHYDES AND KETONES

Overview

  • Reduction converts carbon-oxygen double bonds to single bonds, producing alcohols.

    • Aldehydes lead to primary alcohols.

    • Ketones yield secondary alcohols.

Reagents Used in Reduction Reactions

  • Hydrogen gas (H₂) is a common reagent, requiring a metal catalyst, such as platinum, palladium, or nickel.

Specific Reaction Examples

  • Aldehyde Reaction: Results in primary alcohol through the addition of hydrogen to both carbon and oxygen.

  • Ketone Reaction: Results in secondary alcohol similarly by converting double to single bonds.

TYPES OF REACTIONS: OXIDATION AND REDUCTION

Oxidation Reactions

  • Definition: Characterized by the addition of oxygen or removal of hydrogen.

Reduction Reactions

  • Definition: Characterized by the loss of oxygen or the addition of hydrogen.

Predicting Reaction Products

  • Included examples with hydrogen gas and platinum to demonstrate the reactions.

OVERVIEW OF THE ALEX PROBLEM

Problem Types

  • Two versions concerning carbonyl reduction: predicting reactants and products.