3.1: Nomenclature
- Page ID
- 319703
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Nomenclature
How do we name organic compounds? There are two ways
- common name – colloquial name CHCl3 = chloroform
- IUPAC – “official” international naming system of International Union of Pure and Applied Chemistry CHCl3 = trichloromethane
For starters, we need to know how to describe the atoms and bonds that are depicted using line-angle notation. We use a specific language to describe how many carbons are in a molecule and what kinds of functional groups are in a molecule. Watch the video below for a crash course on this language, which will be followed up with more complicated nomenclature.
Now that you know simple alkane nomenclature and various functional groups, we can begin to discuss more complicated systems.
1. Branched alkanes CnH2n+2 = suffix -ane
a) identify the longest contiguous chain
b) number the chain; start with a substituent group occupying the lowest number possible
c) locate the substituents, give them a number
d) alphabetize
e) if more than one of the same substituent, use following prefixes: 2 = di; 3 = tri; 4 = tetra, 5 = penta; 6 = hexa; 7 = hepta; 8 = octa; 9 = nona; 10 = deca
Example:
12 carbons = dodecane
2,3,5,9-tetramethyl
6-propyl
10-ethyl
Name: 10-ethyl-2,3,5,9-tetramethyl-6-propyldodecane
Example:
IUPAC name: 3-chloro-4-(1-methylethyl)-5-methylheptane
Common name: 3-chloro-4-isopropyl-5-methylheptane
Other common groups (IUPAC names):
nBu = normal butyl (butyl)
tBu = tertiary butyl (1,1-dimethylethyl)
iPr = isopropyl (1-methylethyl)
iBu = isobutyl (2-methylpropyl)
sBu = secondary butyl (1-methylpropyl)
2. Cycloalkanes CnH2n
a) count number of carbons in the ring
b) add prefix “cyclo” to the alkane chain
Examples:
In cycloalkanes, there are often stereoisomers that arise:
3. Bicycloalkanes – a fused or bridged cycloalkane that requires 2 bonds to be broken to become acyclic
a) count # of carbons in the bridged system (do NOT include substituents)
b) add prefix “bicyclo” to parent chain
c) identify bridgehead carbons (ring fusion centers) and count # of intervening carbons in each bridge
d) insert [#.#.#] in between “bicyclo” and parent chain
e) number around the largest ring first, then next largest ring, etc.
f) when two rings are the same size, number ring with substituent first
Examples:
4. Functional groups
If more than one functional group exists, the base or parent name will depend on its priority rank.
IUPAC name: 4-hydroxypentanoic acid (not 4-carboxy-2-butanol - carboxylic acid has higher priority than alcohol!)
Let’s have some practice. What is the IUPAC name for the following molecules?
