10.2: Families/Functional Groups and Prefixes
- Page ID
- 444317
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)- Identify and describe functional groups in organic molecules.
- Use prefixes to identify the number of carbon atoms in an organic molecule
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.
| Family Name |
Functional Group Structure |
Simple Example Structure | Simple Example Name | Name Suffix |
|---|---|---|---|---|
| alkane | none | CH3CH2CH3 | propane | -ane |
| alkene |  |
H2C=CH2 | ethene (ethylene) | -ene |
| alkyne |  |
HC≡CH | ethyne (acetylene) | -yne |
| aromatic |  |
 |
benzene | none |
| alkyl halide |  (X = F, Cl, Br, I) |
CH3CH2Cl | chloroethane | none |
| alcohol |  |
CH3CH2OH | ethanol | -ol |
| ether |  |
CH3CH2–O–CH2CH3 | diethyl ether | none* |
| amine |  |
CH3CH2NH2 | ethylamine | -amine |
| aldehyde |  |
 |
ethanal | -al |
| ketone |  |
 |
propanone (acetone) | -one |
| carboxylic acid |  |
 |
ethanoic acid (acetic acid) | -oic acid |
| anhydride |  |
 |
acetic anhydride | none |
| ester |  |
 |
methyl ethanoate (methyl acetate) | -ate |
| amide |  |
 |
acetamide | -amide |
|
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. |
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In the language of organic chemistry, parent names are used to identify the number of carbon atoms in a molecule. These names may be new to you so take a minute so study Table 10.2.2. While you may not fully understand what "pentane" is yet, from this table hopefully you can see that it an organic molecule with five carbon atoms. (In the next section you will see that the ending "ane" tells you all the carbon atoms are single bonded to each other.)
Looking at Table 10.2.2, notice in the example names that all of the endings are "ane." This will not always be the case. These endings can change but the number of carbon atoms will remain the same. For example, hexane, hexene, hexanol, and hexanoic acid are all organic molecules with six carbon atoms.
| Number of Carbons | Parent Chain (LCC) Name | Example Alkane Name | Example Condensed Structural Formula |
|---|---|---|---|
| 1 | meth- | methane | CH4 |
| 2 | eth- | ethane | CH3CH3 |
| 3 | prop- | propane | CH3CH2CH3 |
| 4 | but- | butane | CH3CH2CH2CH3 |
| 5 | pent- | pentane | CH3CH2CH2CH2CH3 |
| 6 | hex- | hexane | CH3CH2CH2CH2CH2CH3 |
| 7 | hept- | heptane | CH3CH2CH2CH2CH2CH2CH3 |
| 8 | oct- | octane | CH3CH2CH2CH2CH2CH2CH2CH3 |
| 9 | non- | nonane | CH3CH2CH2CH2CH2CH2CH2CH2CH3 |
| 10 | dec- | decane | CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3 |
Practice
To complete the following questions, you can ignore both the numbers before the names as well as the letters at the end of the names. Look at the first three or four letters of the word to determine the number of carbon atoms in the following molecules
- 2-butanol
- 1-propene
- 2-pentanone