Carbon Chapter 4

Chapter 4: Carbon, Bonds, and Functional Groups

Objectives

  • Explain the importance of Carbon

  • Understand the concept of isomers and apply it

  • Familiarity with the various functional groups

Review of Molecules

  • A molecule is composed of atoms linked via chemical bonds.

  • Covalent bonds result from atoms sharing electrons, which can lead to:

    • Polar molecules

    • Non-polar molecules

Carbon and the Molecular Diversity of Life

  • Organic chemistry is the study of carbon compounds.

  • Almost all molecules associated with life contain Carbon.

  • The structure of a carbon atom allows it to form up to four atomic bonds (valence = 4).

  • Carbon's electronegativity enables it to form both polar and nonpolar bonds.

  • Carbon-based molecules are believed to have evolved to form the four types of organic molecules that living things make:

    • Proteins

    • Nucleic acids

    • Carbohydrates

    • Lipids

Isomers

  • Isomers: Variations in the structure of organic molecules with the same molecular formula.

    • Structural Isomers: Differ in the covalent arrangement of atoms.

    • Geometric Isomers: Differ in their spatial arrangement around a C=C bond.

    • Enantiomers: Structures that are mirror images of each other, built around an asymmetric (chiral) carbon atom.

Functional Groups

  • Functional groups are groups of atoms frequently attached to the skeletons of organic molecules.

  • They are the components of organic molecules most commonly involved in chemical reactions.

  • The number and arrangement of functional groups give each molecule its unique properties.

Key Functional Groups

  • Hydroxyl Group (-OH): Found in alcohols; polar due to electronegativity of oxygen.

  • Carbonyl Group (C=O):

    • Aldehyde: At the end of a carbon chain.

    • Ketone: Nested within a carbon chain.

  • Carboxyl Group (-COOH): Acts as acids by forming H+ ions.

  • Amino Group (-NH2):

    • Found in amines; acts as a base.

  • Sulfhydryl Group (-SH):

    • Found in thiols; important for protein stabilization.

  • Phosphate Group (-PO4^{2-}):

    • Found in ATP; usually very reactive.

Detailed Functionality of Functional Groups

Hydroxyl Group

  • Example: Ethanol.

  • Alcohols typically end in -ol.

  • Polar due to oxygen's electronegativity; can form hydrogen bonds with water, aiding in the dissolution of sugars.

Carbonyl Group

  • Ketones (within skeleton) and Aldehydes (at chain end) can be structural isomers.

  • Found in sugars, leading to two major groups: ketoses (with ketone groups) and aldoses (with aldehyde groups).

Carboxyl Group

  • Acts as an acid (donates H+) due to the polarity of the O-H bond.

  • Exists as an ion (carboxylate) in cells with a charge of 1-.

Amino Group

  • Nonionized and Ionized forms exist; acts as a base (can pick up H+).

  • Ionized form carries a charge of +1.

Sulfhydryl Group

  • Forms covalent bonds (cross-linking) which stabilize protein structures.

  • Cysteine cross-linking affects hair texture.

Phosphate Group

  • Contributes negative charge to molecules, aiding reactivity (2- at end, 1- internally).

  • Molecules with phosphate groups can react with water, releasing energy.

Methyl Group

  • Methylated compounds affect gene expression and can influence molecular shapes and functions.