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12.2: Families of Organic Molecules - Functional Groups

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    Learning Objectives

    • Identify and describe functional groups in organic molecules.

    Organic molecules can be classified into families based on structural similarities. Within a family, molecules have similar physical behavior and often have predictable chemical reactivity. The structural components differentiating different organic families involve specific arrangements of atoms or bonds, called functional groups. If you understand the behavior of a particular functional group, you can describe the general properties of that class of compounds.

    The simplest organic compounds are in the alkane family and contain only carbon–carbon and carbon–hydrogen single bonds but do not have any specific functional group. Hydrocarbons containing at least one carbon–carbon double bond, (denoted C=C), are in the alkene family. Alkynes have at least one carbon–carbon triple bond (C≡C). Both carbon–carbon double bonds and triple bonds chemically react in specific ways that differ from reactions of alkanes and each other, making these specific functional groups.

    In the next few chapters, we will learn more about additional functional groups that are made up of atoms or groups of atoms attached to hydrocarbons. Being able to recognize different functional groups will help to understand and describe common medications and biomolecules such as amino acids, carbohydrates, and fats. Table \(\PageIndex{1}\) and Figure \(\PageIndex{1}\) below list several of the functional groups to become familiar with as you learn about organic chemistry.

    Table \(\PageIndex{1}\): Organic Families and Functional Groups
    Family Name

    Functional Group Structure

    		 Simple Example Structure Simple Example Name Name Suffix
    alkane none CH3CH2CH3 propane -ane
    alkene Structural formula of ethylene, showing two carbon atoms connected by a double bond. H2C=CH2 ethene (ethylene) -ene
    alkyne Chemical structure of a carbon-carbon triple bond represented by "C≡C" in red. HC≡CH ethyne (acetylene) -yne
    aromatic Chemical structure of benzene, a hexagonal ring of six carbon atoms with alternating double bonds, depicted in red. A simple black silhouette of a cat sitting upright with its tail curled around its body. benzene none
    alkyl halide A simple black and red logo featuring the letter "X" and a mathematical expression. (X = F, Cl, Br, I) CH3CH2Cl chloroethane none
    alcohol Chemical structure of ethanol, featuring a molecular formula and an -OH hydroxyl group highlighted in red. CH3CH2OH ethanol -ol
    ether Red circular icon with two horizontal lines extending from each side on a black background. CH3CH2–O–CH2CH3 diethyl ether none*
    amine A black background with the letter 'N' in bold red, slightly tilted to the right. CH3CH2NH2 ethylamine -amine
    aldehyde Chemical structure of acetic acid, showing one carbon atom bonded to two oxygen atoms and one hydrogen atom. A simple black silhouette of a cactus with multiple arms and a rounded top. ethanal -al
    ketone Chemical structure of carbon dioxide (CO₂) shown with red lettering and bonds. A black silhouette of a cat sitting with its tail curled around its body. propanone (acetone) -one
    carboxylic acid Chemical structure of acetic acid (CH3COOH) displayed with red atoms and bonds. A simple black line drawing of a light bulb. ethanoic acid (acetic acid) -oic acid
    anhydride Chemical structure of a cyclic compound featuring carbon (C) and oxygen (O) atoms, represented in red. A simple black silhouette of a person raising their arms in a celebratory pose. acetic anhydride none
    ester Chemical structure of a carbon compound featuring two oxygen atoms and one carbon atom, depicted in red. A simple black silhouette of a cat sitting down, facing right. methyl ethanoate (methyl acetate) -ate
    amide Chemical structure of an amino acid with a carbon atom (C) connected to a carboxyl group (O) and an amino group (NH2). A silhouette of a person sitting on a bench under a tree, with a sunset in the background. acetamide -amide
    thiol Logo featuring the word "SHE" in black, with a red dash and "SH" at the end. CH3CH2SH ethanethiol -thiol
    disulfide Text design featuring two stylized "S" letters connected by horizontal lines, colored in red. CH3S–SCH3 dimethyl disulfide none
    sulfide Red letter "S" with horizontal lines above and below, set against a black background. CH3CH2SCH3 ethyl methyl sulfide none

    Atoms and bonds in red indicate the functional group. Bonds not specified are attached to R groups (carbons and hydrogens).

    *Ethers do not have a suffix in their common name; all ethers end with the word ether.

    Organic-Functional-Groups-2016_24ee.pdfOrganic-Functional-Groups-2016.pdfOrganic-Functional-Groups-–-Expanded-v2.png

    Figure \(\PageIndex{1}\): Functional groups in organic chemistry. (CC BY-NC-ND, CompoundChem.com).

    This page titled 12.2: Families of Organic Molecules - Functional Groups is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by Lisa Sharpe Elles.