CHE110_Chapter_16_PowerPoint
Chapter 16 Overview
Learning Changes Everything.®
Lecture Outline prepared by Andrea Leonard, University of Louisiana at Lafayette, Copyright 2022 © McGraw Hill LLC.
16.1 Structure and Bonding
Types of Compounds
Compounds containing a carbonyl group are classified into two broad categories:
Compounds with only C and H atoms bonded to the carbonyl group:
Aldehyde: At least one H atom is bonded to the carbonyl group.
Ketone: Two alkyl groups bonded to the carbonyl group.
Compounds containing electronegative atoms (N or O) bonded to the carbonyl group.
16.2 Nomenclature
A. Naming Aldehydes
IUPAC Naming Process:
Identify the longest carbon chain containing the CHO group.
Change the parent alkane's ending from -e to -al.
Number the chain to position the CHO group at C1 (omit the "1" in the name).
Follow standard nomenclature rules.
Sample Problems (Naming Aldehydes)
Problem 16.1 (Part a)
Solution Steps:
Identify the longest chain containing the CHO.
Name substituents, ensuring the CHO group is at C1.
Problem 16.1 (Part b)
Repeat the solution steps as for part a.
Common Names for Aldehydes
For simple aldehydes, common names are used with the suffix “-aldehyde.”
B. Naming Ketones
IUPAC Naming Process:
Identify the longest chain containing the carbonyl group.
Change the parent alkane's ending from -e to -one.
Number the chain to give the carbonyl carbon the lowest number.
Follow standard nomenclature rules.
Sample Problems (Naming Ketones)
Problem 16.2 (Part a)
Solution Steps:
Identify the longest chain containing the carbonyl group.
Name substituents, ensuring the carbonyl carbon has the lower number.
Problem 16.2 (Part b)
Name the ring, ensuring the carbonyl carbon is at C1.
Common Names for Ketones
Common names are formed by naming both alkyl groups, arranging them alphabetically, and adding “-ketone.”
Examples of Common Names
Some widely used names do not follow the above rule.
16.4 Interesting Aldehydes and Ketones
Formaldehyde
Simplest aldehyde.
Used in synthesis of resins and plastics; sold as formalin (37% aqueous solution for preserving biological specimens).
Acetone
Simplest ketone.
Used as an industrial solvent and starting material for organic polymers.
Produced during the breakdown of fatty acids; high levels found in diabetic patients.
Dihydroxyacetone
Functions as a sunless tanning agent.
Common sunscreen ingredients include avobenzone, oxybenzone, and dioxybenzone.
16.3 Physical Properties
Carbonyl Compounds
Aldehydes and ketones exhibit interactions wherein a negatively charged carbonyl oxygen of one molecule associates with a positively charged carbonyl carbon of another.
Boiling Points
Comparing boiling points:
Pentane (5 carbon alkane): 36°C
Butanal (4 carbon, one carbonyl): 76°C
1-Butanol (4 carbon, with an OH group): 118°C
16.5 Reactions of Aldehydes and Ketones
Treatment with Tollen's reagent alters aldehydes into carboxylic acids without affecting alcohols.
16.6 Reduction of Aldehydes and Ketones
Reduction process:
Aldehyde → primary alcohol (one bond of C=O is broken).
Ketone → secondary alcohol (similar process).
16.8 Acetal Formation
Hemiacetal vs. Acetal
Hemiacetal: Contains one OH and one OR group bonded to a central carbon.
Acetal: Contains two OR groups bonded to a central carbon.
Reactions Involving Ethanol and Hemiacetals
Reaction of an aldehyde with ethanol produces a hemiacetal, which can further react to form an acetal.
In the case of a 5-membered carbon ring involving a ketone, the reaction with ethanol also produces a hemiacetal that can transform into an acetal.
Structural Changes
Structural rearrangements result from reactions involving water and acids, leading to formation or decomposition of acetals and hemiacetals.