1. ! Review Chapter 12 of Nomenclature of Alkanes
• Straight-chain alkanes are named by counting the number of C atoms in the
backbone and adding the family suffix -ane
• Branched chain alkanes can be named in the following 4 steps.
STEP 1: Name the main chain. Find the longest continuous chain of carbons,
and name the chain according to the number of carbon atoms it contains.
The longest chain may not be immediately obvious because it is not always
written on one line; you may have to “turn corners” to find it.
STEP 2: Number the carbon atoms in the main chain. Begin at the end nearer
the first branch point:
STEP 3: Identify the branching substituents, and number each according to
its point of !
attachment to the main chain:
If there are two substituents on the same carbon, assign the same number to
both. There must always be as many numbers in the name as there are
substituents.
STEP 4: Write the name as a single word, using hyphens to separate the
numbers from !the different prefixes and commas to separate numbers if
necessary. If two or more different substituent groups are present, cite them in
alphabetical order.
If two or more identical substituents are present, use one of the prefixes di-, tri-,
tetra-, and so forth, but do not use these prefixes for alphabetizing purposes.
• Cycloalkanes are named by a straightforward extension of the rules for naming
open-chain alkanes. In most cases, only two steps are needed.
STEP 1: Use the cycloalkane name as the parent. That is, compounds are
named as alkyl-substituted cycloalkanes rather than as cycloalkyl substituted alkanes . If there is only one substituent on the ring, it is not
even necessary to assign a number because all ring positions are identical.
STEP 2: Identify and number the substituents. Start numbering at the group
that has alphabetical priority, and proceed around the ring in the direction
that gives the second substituent the lower possible number.
Lets do some examples!
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Chapter Objectives
1.!
What are alkenes, alkynes, and aromatic compounds? Be able to recognize the
functional groups in these three families of unsaturated organic compounds and give
examples of each.!
2.!
How are alkenes, alkynes, and aromatic compounds named? Be able to name an
alkene, alkyne, or simple aromatic compound from its structure, or write the structure,
given the name.!
3.!
What are cis–trans isomers? Be able to identify cis –trans isomers of alkenes and
predict their occurrence.
4.!
What are the categories of organic reactions? Be able to recognize and describe
addition, elimination, substitution, and rearrangement reactions.!
5.!
What are the typical reactions of alkenes, alkynes, and aromatic compounds? Be
able to predict the products of reactions of alkenes, alkynes, and aromatic
compounds.!
6.!
How do organic reactions take place? Be able to show how addition reactions
occur.
1.!
What are alkenes, alkynes, and aromatic compounds?
alkenes:
alkynes:
aromatic compounds:
Saturated:
Unsaturated:
2.!
How are alkenes, alkynes, and aromatic compounds named?
STEP 1: Name the parent compound. Find the longest chain containing the
double or triple bond, and name the parent compound by adding the suffix ene or - yne to the name for the main chain.
The number of multiple bonds is indicated using a numerical prefix ( diene = 2
double bonds, triene = 3 double bonds, and so on) when there is more than
one.
STEP 2: Number the carbon atoms in the main chain, beginning at the end
nearer the multiple bond. If the multiple bond is an equal distance from both
ends, begin numbering at the end nearer the first branch point.
Cyclic alkenes are called cycloalkenes . The double-bond carbon atoms in
substituted cycloalkenes are numbered 1 and 2 so as to give the first
substituent the lower number:
STEP 3: Write the full name. Assign numbers to the branching substituents ,
and list the substituents alphabetically.
Use commas to separate numbers and hyphens to separate words from
numbers.
Indicate the position of the multiple bond in the chain by giving the number of the
first multiple-bonded carbon. If more than one double bond is present,
identify the position of each and use the appropriate name ending (for
example, 1,3-butadiene and 1,3,6-heptatriene).
For historical reasons, there are a few alkenes and alkynes whose names do not
conform strictly to the rules.
Lets do some examples!
3.!
What are cis–trans isomers? Isomers:
cis-trans Isomers: