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4.1-4.3 IUPAC Nomenclature of
Alkanes, alkyl halides, and alcohols
- When only a finite number of organic molecules
were known, common names were given.
- We now need a “language” as a systematic way
to name compounds and determine structure
based on name.
- International Union of Pure and Applied Chemistry
- Gives each compound an un-ambiguous name
- PRACTICE, PRACTICE, PRACTICE!!!!!!!!!
- Read sections 4.1-4.2 (except bicyclic), 7.2, 7.7,
9.2 do ALL problems within these sections at the
end of the chapters AND the drill manual AND
any others you find!!!!
Names for Unbranched Alkanes
- Table 4.1 should become your best friend (C
- Root names are the same for any
hydrocarbon or substituted hydrocarbon
based on number of Carbon atoms in the
chain.
- Root + “ane” ending is for alkANEs
- Here are those important to you now.
Unbranched Alkyl Groups
- Remove one H from an alkane: alkyl group
- Groups are named with “root” + “-yl”
- For unbranched, names are intuitive
Alkane Alkyl
group
Ab
methane CH 3 -H methyl^ CH 3 - Me
ethane CH 3 CH 2 -H ethyl^ CH 3 CH 2 - Et
propane CH 3 CH 2 CH 2 -H propyl^ CH 3 CH 2 CH 2 - Pr
butane CH 3 CH 2 CH 2 CH 2 -H butyl^ CH 3 CH 2 CH 2 CH 2 - Bu
Branched Chain Alkanes
1. Locate the longest continuous chain of C
atoms. This is the “parent chain.” Note: The
parent chain may not be drawn in a straight
line.
CH 3 CH 2 CH 2 CH 2 CHCH 3
CH 3
CH 3 CH 2 CH 2 CH 2 CHCH 3
CH 2
CH 3
Branched Chain Alkanes
3. Used the numbers obtained from Rule #2 to
designate the location of the substituent group.
CH 3 CH 2 CH 2 CH 2 CHCH 3
CH 3
methyl
CH 3 CH 2 CH 2 CH 2 CHCH 3
CH 2
CH 3
methyl
Branched Chain Alkanes
- When 2+ substituents are present, give each sub. a number corresponding to its position on the parent chain. Substituents are listed alphabetically in the name DISREGARDING prefixes (ex: di- and tri-)
CH 3 CHCH 2 CH 2 CHCH 2 CH 3
CH 2
CH 3
CH 3
Branched Chain Alkanes
6. When 2+ subs. are identical, indicate this by the use
of prefixes di-, tri-, tetra-
Make sure each sub. has a number. Separate
numbers with a comma.
CH 3 CHCHCH 3
CH 3
CH 3
CH 3 CHCHCHCH 3
CH 3 CH 3
CH 3
CH 3 CCH 2 CCH 3
CH (^3) CH 3
CH 3 CH 3
Branched Chain Alkanes
7. When 2 chains of equal length compete for
selection as the parent chain, choose the chain
with the greater number of substituents.
Branched Chain Alkanes
8. When branching first occurs at an equal distance
from either end of the longest chain, chose the
name that gives the lower number at the first
point of difference.
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Nomenclature of Branched Alkyl Groups
- Remember names of unbranched alkyl groups (1 H
removed from terminal C)
- If a compound has >2 C atoms, an internal H can be
removed and more than one substituent group is possible.
CH 3 CH 2 CH 3
CH 3 CH 2 CH 2
CH 3 CHCH 3
propane
propyl group
1-methyl ethyl or isopropyl group
4.4 Nomenclature of Cycloalkanes
- Cylcoalkanes are named as the alkane
with “ cyclo” as the prefix
- If only one sub is on the ring, no need to
number it
- If 2+, number the 1 st^ ABC as one and
move in the direction to give the next sub
the lowest possible number(s).
- When a ring system is attached to a chain
with a greater number of Cs, then name as
cycloalkylalkanes
Cl
Substituent groups
