organic naming rules 2
TRANSCRIPT
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Organic Naming Rules
AP Chemistry 439
For complete Rules go to:
http://www.acdlabs.com/iupac/nomenclature/
http://www.acdlabs.com/iupac/nomenclature/http://www.acdlabs.com/iupac/nomenclature/ -
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Organic Compounds
Consist of mainly four
elements
Carbon
Hydrogen
Oxygen
Nitrogen
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Why Do We Need a Separate Set
of Rules? Examine some typical organic compounds
CH4
C2H6
Name these using typical covalent rules
Carbon tetrahydride
Dicarbon hexahydride
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So?
That wasnt so bad, right?
How about these:
C4H10
C5H12
See my point?
Tetracarbon decahydride
Pentacarbon ??? hydride
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Isomers
If thats not enough, how about this one:
C
H
H
C
H
H
C
H
H
C
H
H
H H
Formula?
C4H
10
C
H
H
C
H
HC
H
HCH
H
H
H
Formula?
C4H
10
DifferentStructure
Same
Formula
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Overall Problems
Memorizing too manyprefixes for largenumbers
Different chemicalshaving the sameformulas
Keep in mind that thusfar weve only dealtwith TWO differentelements!
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So what to do?
Number of hydrogens is going to be the
same, regardless of isomerism
C
H
H
C
H
H
C
H
H
C
H
H
H HC
H
H
C
H
H
C
H
H
C
H H
C
H
H
H H
C
H
H C HH
C
H
H
C
H H
C
H
H
H
H
CH
H
C5H12C5H12
C5H12
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Solution
Since number of
hydrogens dont change
with isomerism, why
bother naming them?
Name the molecule simply
based on number of
CARBONS
We can always add
prefixes or suffixes later
for differentiation
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Name based on number of
Carbons 1
2
3
4
5
6
7
8
9
10
Methane
Ethane
Propane
Butane
Pentane
Hexane
Heptane
Octane
Nonane
Decane
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Did that Really Help?
C
H
H
C
H
H
HH
C
H
H
HH Carbon tetrahydride becomes: Methane
Dicarbon hexahydride becomes: Ethane
C
H
H
C
H
H
C
H
H
C
H
H
H HC
H
H
C
H
H
C
H
H
C
H
H
CH4
C2H6
Octacarbon ???hydride becomes:
Octane
C8H18
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Branches Straight-chain alkanes (Just C & H with
single bonds) are now easy
C
H
H
C
H
H
C
H
H
C
H
H
H H C4H10 Butane
But how do we deal with branches?
C
H
H
C
H
HC
H
HCH
H
H
H
C4H10 ????
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Rules pt. 2
Identify the longest unbranched
chain ofcarbons
Name it as normal
Identify the branch
Name it but give it a yl
suffix
Put the names of all branchesfirst, then put name of longest
chain
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Example
C
H
H
C
H
HC
H
HCH
H
H
HLongest unbranched
chain of carbons is
three long
propane
Branch is one long methyl
Methyl Propane
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Practice
C
H
H
C
H
H
C
H
H C
H
H
H
C
H
H H
Methylbutane
H H H H H
C
H
C
H
CH C
H
C
H
H
C HH
C
H
HH
Ethylpentane
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One More Practice
C C C
C
C
C C C
C
C
It doesnt matterwhich way you go!
(Provided you correctly pickthe longest unbranched chain)
MethylButane
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Be Careful
H
C C C C CH H H H
H H H H
HH
CH H
CH
HH
Hexane
This is your
longest
uninterruptedchain
Methyl
Methyl Hexane
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A Small Wrinkle
H
C C C C CH H H H
H H H H
HH
CH HH
H
C C C C CH H H H
H H H H
HH
CH HH
MethylPentane
MethylPentane
These are different molecules, though!!!
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So Now What?
Since two different
molecules cant have
the same name, wemust differentiate
If we look closely,
though, the only
difference betweenthem is theposition of
the methyl group
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Positioning
H
C C C C CH H H H
H H H H
HH
CH HH
H
C C C C CH H H H
H H H H
HH
CH HH
Here the methyl group
is on the second carbonfrom the end
Here the methyl group
is on the third carbonfrom the end
MethylPentane MethylPentane
So
2- 3-
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Rules pt. 3
Identify the longest unbranchedchain ofcarbons
Name it as normal
Identify the branch
Name it but give it a yl suffix
Put the names of all branchesfirst, then put name of longest
chain Put the numberof the carbon the
branch is on (start numberingfrom the closest single end)
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Practice
H
C C C C CH H H H
H HH H
HH
CH HH
CH
H
CH
H
H
C C C C CH H H H
H H H H
HH
CH H
H
C CH H
H H
CH
H
2-methyl heptane
4-methyl octane
H
C C C CH H H
H H H
H
CH H
H
CH
H
HCH
H 2-methyl hexane
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Multiple Branches
So far weve only had
one branch
What happens whenthere are multple
branches?
Just add a prefix to
indicate the numberof
a particular type of
branch
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Practice
H
C C C C C
H H H
H HH H
HH
CH HH
C
H
HC
H
H
CH H
H
heptane
methyl
methyl2-
2-
2-methyl, 2-methyl heptaneSounds redundant
2,2 dimethyl heptane
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More Practice
CH HH
H
C C C C CH H H
H H H H
HH C CH H
HH
CH
H
CH H
H
C C C C CH H H
H H H
HH
CH HH
H
CH H
CH H
H
CH HH
2, 6-dimethyl
octane
3 ethyl-2,4-
dimethyl pentane
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Is your arm sore yet?
Are you sick to death
of writing all those
carbons? Even worse, are you
sick of writing all
those Hydrogens?
How about this
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Shorthand notation
C
H
H
C
H
H
C
H
H
C
H
H
H HKeep in mind that we have been
ignoring the hydrogens for a long
time.
Our names have been based
entirely on the positioning of the
carbons.
So lets now ignore the hydrogens
completely!
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Is it that easy?
H
C C C C CH H H H
H HH H
HH
CH H
H
CH
H
CH
H
CH HH
H
C C C C CH H H
H H H H
HH C CH H
HH
CH
H
CH H
H
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One More
C C C C C
H H H
H H H
HH
CH HH
H
CH H
CH H
H
CH HH
CH
H
Shorthand notation?
Name?
3-ethyl-2,4 dimethyl hexane
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So is that it?
Not even close!!
There are literally
millions of differentorganic compounds.
What else can we do
to make things more
complicated?
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Rings
Thus far we have dealt
with chains that are
straight or branched. If hydrocarbons are
long enough, one end
can wrap around and
link up with itself!
We call these cyclic
hydrocarbons.
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Cyclic Hydrocarbons
Name the molecule as
normal
Add the prefix cyclo-to the front of the
name of the longest
chain
Start numbering from
the most important
branch in the ring
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Examples
Cyclohexane
Cyclooctane
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More Examples
Methyl cyclopentane
1,2 dimethyl
cyclohexane
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Try These
1 ethyl, 3 methyl
cyclobutane
3 methyl, 1 propylcylclohexane
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Multiple Bonds
So far, even with thecyclic structures wehave dealt only with
single bonds
Carbon can makemultiple bonds toanother carbon
This changes the name
Why?
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Examine Structures
C
H
H
C
H
H
H H C2H6 Ethane- notice that eachcarbon has four bonds
What will happen to the structure if we double bond the two carbons?
C
H
C
H
H H
C2H4 Each carbon still has fourbonds BUT now the
hydrogens have changed!!
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Naming molecules with multiple
bonds Name the molecule as
normal
Change the suffix of the
longest chain name
Double bonds = ene
Triple bonds = yne
Use numbering and
prefixes for positioning
and multiple multiple
bonds.
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So.
C
H
H
C
H
H
H H C
H
C
H
H H C CH H
C2H6 C2H4 C2H2
ethane ethene ethyne
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Practice
C C C CH H
H H H
H
H
CH H
H
CH
H 3 methyl-1-pentene
H
H
C C C C CH H H H
H H H
H CH
H
CH
H
2-heptene
H
H
C CH
H
H CH
CH
H
1-butene
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How about in Shorthand?
Notice the twolines means the
double bond is
there!
2 pentene
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Practice!
Methyl propene
2,4-dimethyl-2-pentene
3-ethyl-2,4,4-trimethyl-1-pentene
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Tough Ones
2 methyl 1,3 butadiene
1,2dimethyl-1,4 cyclohexadiene
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Triples?
3, 3-dimethyl-1-butyne
1,4 cyclohexadiyne
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So thats it, right?
Not even close, bud.
All this.all this was
just for two elements,carbon and hydrogen!!
We havent even dealt
with any of the others,
yet.
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Wait!! Dont jump!!
Get off that bridge.
Its not that bad
provided we arrangethings in an organized
fashion!
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Functional Groups
Nature has done us afavor.
There are manycommon groups thatwe can organized orfile into differentcategories.
Then we can namethem based on thesecategories.
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Functional Groups
A group of atoms that, when added to a
hydrocarbon chain, alter the chemical
properties of the chain. Just a few different functional groups to
know
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Functional Groups
Halogens
Alcohols
Ethers Aldehydes
Ketones
Carboxylic Acids Esters
Amines
R-F, R-Cl, R-Br, R-I
R-OH
R-O-R R-COH
R-CO-R
R-COOH R-COO-R
R-NH2
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Halides
Fluorides, Chlorides,
Bromides, and Iodides
Simply name themolecule as normal
but add the prefix
Fluoro, Chloro,
Bromo, or Iodo asnecessary
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Halides
Cl
Cl
2, 3 dichlorohexane
I
I
3, 3 diiodo-1-pentene
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Alcohols
R-OH
Name like normal
except add anolsuffix
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AlcoholsOH
OHC
H
H
C
H
H
H
OH
2 propanol
ethanol
1cyclobutenol
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Ethers
R-O-R
Name two R groups
withyl endings End name in ether
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Ethers
ODimethyl ether
O Ethyl methyl ether
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Aldehyde
R-COH
This is a carbon to
oxygen double bondwith a hydrogen at the
end.
Name as normal
except use a -alsuffix
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Aldehydes
C
H
H
C
H
H
C
H
H
CH H
O
butanal
C
H
H
C
Cl
Cl
C
H
H
C H
O
C
H
H
H 3,3 dichloropentanal
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Ketones
R-CO-R
This is a carbon to
oxygen double bondbut in the center of a
hydrocarbon chain
rather than the end
Name as normal butgive it a -one suffix
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Ketones
propanone
2 hexanone
C
H
H
C
H
H
CH H
O
C
H
H
C
H
H
C
H
H
C
O
C
H
H
H C
H
H
H
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Carboxylic Acids
R-COOH or R-CO2H
This is a carbon to
oxygn double bondwith the same carbon
single-bonded to an
OH group.
Name as normalexcept give it the
suffix -anoic acid.
H
C2H3O2
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Carboxylic Acids
C
H
H
C
H
H
C
H
H
CH OH
O
Butanoic acid
C
H
H
C
H
H
FC
O
HO 3-Fluoropropanoic acid
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Esters
R-COO-R
This is a carbon to oxygen
double bond with a carbon
to oxygen single bondedto another single bonded
carbon
Name by given secondary
branch -yl suffix andmain branch -anoate
suffix.
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Esters
C
H
H
C
H
H
C
H
H
C
O
C
H
H
H C
H
H
HO
Secondary
BranchMain Branch
methylpentanoate
Methyl Pentanoate
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Esters
C
H
H
H C
H
H
C
O
C
H
H
O C
H
H
HC
H
H
C
H
H
Butylpropanoate
C
H
H
H O
H
H
C
O
C
H
H
C C
H
H
HC
H
H
C
H
H
Methyl hexanoate
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Amines
R-NH2
Name the R group
or groups with -ylendings
Add the word amine
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Amines
C
H
H
N
H
H
H Methylamine
C
H
H
N
C
H
H
HH
H Dimethylamine
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Summary
ClR
Halide
OHR
Alcohol
RR O
Ether
HR C
Aldehyde
O
RR C
Ketone
O
OHR CCarboxylic
Acid
O
OR CEster
O
R NH2R
Amine
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Alkanes
Alkenes
Alkynes
Halides Alcohols
Ethers
Aldehydes
Ketones Carboxylic Acids
Esters
Amines
Summary
- -ane
= -ene
-yne
R-X -o R-OH -ol
R-O-R -yl ether
R-COH -al
R-CO-R -one R-COOH -anoic acid
R-COO-R -yl -anoate
R-NH2 -yl amine
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Can You Do This?
YES!
It takes:
Memorization
Practice
Practice
Practice
Practice And, oh yes
Practice!