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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 clipboard_ebd253a6e4db6b69e36382d896d43ca8d.png H2C=CH2 ethene (ethylene) -ene
    alkyne clipboard_e5d260ec8b430ccf9c0d628965e7dc212.png HC≡CH ethyne (acetylene) -yne
    aromatic clipboard_e0bf98d68d8680205ca5b522279305771.png clipboard_e7aa881c96f4917175c54ae1b0bc344d5.png benzene none
    alkyl halide clipboard_e0e94be8b5e8e8322a7cddae4462da886.png (X = F, Cl, Br, I) CH3CH2Cl chloroethane none
    alcohol clipboard_e3e3100b63a583b9fdaa8ee8438c0564b.png CH3CH2OH ethanol -ol
    ether clipboard_e2df9d10f296da57128f4bf8851153139.png CH3CH2–O–CH2CH3 diethyl ether none*
    amine clipboard_e5c7c513ea24f80b81f55d181bbb675da.png CH3CH2NH2 ethylamine -amine
    aldehyde clipboard_ea8f50753926a1541ca7803328144faf3.png clipboard_e78928d97d84b75b8ef575ae61b84d0a3.png ethanal -al
    ketone clipboard_e11d2dbb471a80f1c6504067d841f1e21.png clipboard_e3ee6cb6fc3dc1a4e7a7726b8ac18c590.png propanone (acetone) -one
    carboxylic acid clipboard_ec2196234e57a448603730446173c2252.png clipboard_e546afb8a2f697cec03fd27256ee4d1be.png ethanoic acid (acetic acid) -oic acid
    anhydride clipboard_e47c600d87a44c91e2ef24411d1801e54.png clipboard_e4500e8d211ca78c71e9c8fe4b53f68dc.png acetic anhydride none
    ester clipboard_ed32b122c068f4c5f251cb75c8054d708.png clipboard_e7e9dac28bf1a814e69cfb9da176cb4e5.png methyl ethanoate (methyl acetate) -ate
    amide clipboard_e6ce7fc20e9f03da219454282c2518861.png clipboard_ec1eb960a2bb8cd8037634b334d22d4e2.png acetamide -amide
    thiol clipboard_edd73e181748655020a846c380d7342c1.png CH3CH2SH ethanethiol -thiol
    disulfide clipboard_ed1774522fae2b15531ff636b38be0cb2.png CH3S–SCH3 dimethyl disulfide none
    sulfide clipboard_e43054ea1e2a63310fd48eb69bec79741.png 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.