Chapter 12: The Common Carbonyl-Containing Groups Study Notes

CHAPTER 12: THE COMMON CARBONYL-CONTAINING GROUPS

12.1 CARBONYL CONTAINING FUNCTIONAL GROUPS

  • Definition:

    • Carbonyl group: oxygen double bonded to a carbon (C=O)

    • A component of various functional groups.

CARBONYL-CONTAINING GROUPS (Know these 5):

  1. Aldehyde: General structure - RCHO

  2. Ketone: General structure - RCOR'

  3. Carboxylic Acid: General structure - RCOOH

  4. Ester: General structure - RCOOR'

  5. Amide: General structure - RCONH2, RCONHR, or RCONR2

Properties of Carbonyl Groups

  • Geometry: Trigonal planar

  • Polarity: C=O bond is polar; interacts well with other polar compounds.

  • Solubility: Many carbonyl compounds are soluble in water.

12.2 ALDEHYDES

General Structure

  • Structure: R-CHO

  • Example molecules:

    • Cinnamaldehyde

    • Methanal (formaldehyde): HCHO

    • Ethanal (acetaldehyde): CH3CHO

    • Propanal: CH3CH2CHO

Properties of Aldehydes

  • Are polar molecules.

  • Do not form hydrogen bonds with each other.

  • Can form hydrogen bonds with water.

  • Less soluble than alcohols but more soluble than hydrocarbons of similar size.

IUPAC Nomenclature for Aldehydes

  1. Assign the root: The longest carbon chain containing the C=O group.

  2. Assign the ending: Replace “-e” at the end of the alkane name with “-al”.

  3. Assign the prefix: Carbonyl C is assigned as # 1.

Naming Aldehydes Examples

  • Methanal (formaldehyde)

  • Ethanal (acetaldehyde)

  • Propanal (CH3CH2CHO)

Clicker Questions about Aldehydes

  1. What is the common name of the smallest aldehyde?

    • Ans: Methanal (formaldehyde).

12.3 KETONES

General Structure

  • Structure: RC(O)R'

    • Example general structure: H-C-C-C-C-C-H

Properties of Ketones

  • Polar molecules.

  • Serve as good organic solvents.

  • Used in treatments (e.g., Prednisone: a synthetic steroid).

IUPAC Nomenclature for Ketones

  1. Assign the root: The main chain must contain the C=O group.

  2. Assign ending: Replace “-e” from the alkane name with “-one”.

  3. Assign locator number: Indicate where the carbonyl group is located in the chain (e.g., alkan-#-one).

  4. Assign prefix: Name substituents.

Clicker Question on Ketones

  • Identify the correct IUPAC name for the given structure.

Naming Aldehydes and Ketones Practice

  • Practice naming specified aldehydes and ketones from structures.

Solubility and Boiling Points of Aldehydes and Ketones

  • Solubility: Aldehydes and ketones with 3-4 C atoms are generally soluble in water due to their ability to form hydrogen bonds.

  • Boiling Points: They have higher boiling points than similar-sized alkanes but lower than alcohols.

12.4 CARBOXYLIC ACIDS

General Structure

  • Structure: RCOOH

    • Distinction: Not an alcohol; generally have unpleasant odors.

    • Example: Carbonyl carbon, aromatic carbon, etc.

Ionization of Carboxylic Acids

  • Can lose a proton (H+) to form a carboxylate ion (RCOO−).

  • Names end in “-ate ion.”

Solubility of Carboxylic Acids

  • Most soluble in water with 5-6 C atoms due to hydrogen bond formation.

  • Elevated boiling points relative to similar MW alkanes, aldehydes/ketones, and alcohols.

Carboxylic Acids in Nature and Pharmaceuticals

  • Examples include fatty acids, citric acid (found in fruits), and NSAIDs like ibuprofen.

Naming Carboxylic Acids

  1. Assign root.

  2. Replace “-e” with “-oic acid”.

  3. Assign prefix: Carbonyl C is # 1.

12.5 ESTERS

General Structure

  • Structure: RCOOR'

  • Formed when -OH group of carboxylic acid is replaced with -OR'.

  • Characteristics: Found in fragrances, insoluble in water, contain a polar group.

Naming Esters

  1. Assign the root to the carbon chain with the C=O group (C # 1).

  2. Drop the “-e” and add “-oate” for the parent name.

  3. Name the R group on the O as a substituent.

Examples of Esters and Their Properties

  • Many common esters possess characteristic fruity or spicy odors.

12.6 AMIDES

General Structure

  • Structure: RCONH2, RCONHR, or RCONR2

  • Amides are neutral molecules and include the amide functional group found in proteins.

Naming Amides

  1. Assign the root.

  2. Replace “-e” with “-amide”.

  3. Name R groups on the N as substituents (prefix: N-).

Additional Concepts Related to Functional Groups

Boiling Points

  • Higher intermolecular forces result in higher boiling points (e.g., hydrogen bonding).

Solubility of Organic Molecules in Water

  • Solubility depends on polarity and the presence of O or N.

Clicker Questions Recap

  • Various clicker questions related to functional groups, nomenclature, and compounds with specified structures.

Problem Sets

  1. Name compounds based on provided structures.

  2. Classify alcohols, esters, and other functional groups from given examples.

End of Chapter Summary

This chapter covered carbonyl-containing groups including aldehydes, ketones, carboxylic acids, esters, and amides, their structures, properties, naming conventions, and real-world applications in natural products and pharmaceuticals.