Organic Naming Rules Chem 332 For complete Rules go to:
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Transcript of Organic Naming Rules Chem 332 For complete Rules go to:
Organic Naming Rules
Chem 332
For complete Rules go to:
http://www.acdlabs.com/iupac/nomenclature/
Organic Compounds
• Consist of mainly four elements
• Carbon
• Hydrogen
• Oxygen
• Nitrogen
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
So?
• How about these:• C4H10
• C5H12
• See my point?
Tetracarbon decahydride
Pentacarbon ??? hydride
Isomers• If that’s not enough, how about this one:
C
H
H
C
H
H
C
H
H
C
H
H
H H
Formula?
C4H10
C
H
H
C
H
HC
H
HCH
H
H
H
Formula?
C4H10
Different Structure
Same Formula
Overall Problems
• Memorizing too many prefixes for large numbers
• Different chemicals having the same formulas
• Keep in mind that thus far we’ve only dealt with TWO different elements!
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
C
H
H
C5H12C5H12
C5H12
Solution
• Since number of hydrogens don’t 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
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
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:
OctaneC8H18
Alkanes• Alkanes are hydrocarbons
that contain only single bonds.
• The general formula for alkanes is: CnH2n+2
• n represents the number of carbon atoms in the molecule
Some Practice
• What is the formula for an alkane that has 6 carbon atoms?
• Use the general formula to figure this out.• Draw out the dot structure for this
molecule.• Do all carbon atoms share 4 times?• Do all hydrogen atoms share 1 time?
Hmm, not too bad!If there are 6 carbon atoms,
then the H atoms must equal 14
Formula = C6H14 Hexane
Dot Structure
C – C – C – C – C – C
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
HC
H
HC
H
HCH
H
H
H
C4H10 ????
Rules pt. 2
• Identify the longest unbranched chain of carbons
• Name it as normal• Identify the branch
• Name it but give it a “–yl” suffix• Put the names of all branches
first, then put name of longest chain
Example
C
H
HC
H
HC
H
HCH
H
H
HLongest unbranched chain of carbons is
three long
propane
Branch is one long methyl
Methyl Propane
Practice
C
H
H
C
H
H
C
H
H C
H
H
H
C
H
H H
Methyl butane
H H H H H
C
H
C
H
CH C
H
C
H
H
C HH
C
H
HH
Ethyl pentane
One More Practice
C C C
C
C
C C C
C
C
It doesn’t matter which way you go!(Provided you correctly pick the longest unbranched chain)
Methyl Butane
Be CarefulH
C C C C CH H H H
H H H H
HH
CH H
CH
HH
HexaneThis is your longest uninterrupted chain
Methyl
Methyl Hexane
A Small Wrinkle
H
C C C C CH H H H
H H H H
HH
CH H
H
H
C C C C CH H H H
H H H H
HH
CH H
H
Methyl Pentane
Methyl Pentane
These are different molecules, though!!!
So Now What?
• Since two different molecules can’t have the same name, we must differentiate
• If we look closely, though, the only difference between them is the position of the methyl group
Positioning
H
C C C C CH H H H
H H H H
HH
CH H
H
H
C C C C CH H H H
H H H H
HH
CH H
H
Here the methyl group is on the second carbon from the end
Here the methyl group is on the third carbon from the end
Methyl Pentane Methyl Pentane
So…
2- 3-
Rules pt. 3
• Identify the longest unbranched chain of carbons
• Name it as normal• Identify the branch
• Name it but give it a “–yl” suffix• Put the names of all branches
first, then put name of longest chain
• Put the number of the carbon the branch is on (start numbering
from the closest single end)
Practice
H
C C C C CH H H H
H HH H
HH
CH H
H
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
Multiple Branches
• So far we’ve only had one branch
• What happens when there are multple branches?
• Just add a prefix to indicate the number of a particular type of branch
Practice
H
C C C C CH H H
H HH H
HH
CH H
H
CH
H
CH
H
CH H
H
heptane
methyl
methyl2-
2-
2-methyl, 2-methyl heptaneSounds redundant
2,2 dimethyl heptane
More Practice
CH H
H
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 H
H
H
CH H
CH H
H
CH H
H
2, 6-dimethyl octane
3 ethyl-2,4-dimethyl pentane
Multiple Bonds
• So far, even with the cyclic structures we have dealt only with single bonds
• Carbon can make multiple bonds to another carbon
• This changes the name
• Why?
Examine Structures
C
H
H
C
H
H
H H C2H6Ethane- notice that each carbon has four bonds
What will happen to the structure if we double bond the two carbons?
C
H
C
H
H HC2H4
Each carbon still has four bonds BUT now the hydrogens have changed!!
Alkenes
• Alkenes contain a double bond in the molecule.
• The general formula for alkenes is CnH2n
A little practiceA little practice..
• What is the formula for an alkene with 4 carbons?
• Draw the dot structure.• You can place the double bond between any
two carbons since it wasn’t specified.
Wow, I can do this!Wow, I can do this!
• The formula is C4H8 Butene
• The dot structure is
C – C = C – C
Alkynes
• Alkynes contain a triple bond in the molecule.
• The general formula for alkynes is CnH2n-2
Some more practice.
• What is the formula for an alkyne with 7 carbons?
• Draw the dot structure.• You can place the triple bond between any
two carbons since it wasn’t specified.
I am so smart!
• The formula is C7H12 Heptyne
• The dot structure is
C – C ≡ C – C – C – C – C
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.
So….
C
H
H
C
H
H
H H C
H
C
H
H H C CH H
C2H6 C2H4 C2H2
ethane ethene ethyne
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
1-
2-
3-
4-
5-
6-
7-
8-
9-
10-
Mono
Di
Tri
Tetra
Penta
Hexa
Hepta
Octa
Nona
Deca
Prefixes for #’s of groups
1-
2-
3-
4-
5-
6-
7-
8-
9-
10-
Meth
Eth
Prop
But
Penta
Hexa
Hepta
Octa
Nona
Deca
Prefixes for #’s of CARBONS
Suffixes Single
Double
Triple
-ane
-ene
-yne
Circles use Cyclo-
1. Identify the longest chain (it must contain the double or triple bond if present)
2. Name it as normal
3. If Double or triple bonds are present use the correct suffix and identify the starting position with a number
4. Identify the branches
5. Name any branches by using carbon prefixes and –yl suffixes and identify their positions with a number
6. Add a prefix to indicate multiple branches using the groups prefixes
Branches use -yl
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…
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!
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 H
H
H
C C C C CH H H
H H H H
HH C CH H
HH
CH
H
CH H
H
One More
C C C C CH H H
H H H
HH
CH H
H
H
CH H
CH H
H
CH H
H
CH
H
Shorthand notation?
Name?
3-ethyl-2,4 dimethyl hexane
So is that it?
• Not even close!!• There are literally millions of different
organic compounds.• What else can we do
to make things more complicated?
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.
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
Examples
Cyclohexane
Cyclooctane
More Examples
Methyl cyclopentane
1,2 dimethyl cyclohexane
Try These
1 ethyl, 3 methyl cyclobutane
1 propyl, 3 methyl cylclohexane
How about in Shorthand?
Notice the two lines means the double bond is there!
2 pentene
Practice!
Methyl propene
2,4-dimethyl-2-pentene
3-ethyl-2,4,4-trimethyl-1-pentene
AP Area
• Unless you are a chemist, or in AP Chem you don’t need to worry about this
Tough Ones
2 methyl 1,3 butadiene
1,2 dimethyl-1,4 cyclohexadiene
Triples?
3, 3-dimethyl-1-butyne
1,4 cyclohexadiyne
So that’s it, right?
• Not even close, bud.• All this….all this was
just for two elements, carbon and hydrogen!!
• We haven’t even dealt with any of the others, yet.
Wait!! Don’t jump!!
• Get off that bridge.• It’s not that bad
provided we arrange things in an organized fashion!
Functional Groups
• Nature has done us a favor.
• There are many common groups that we can organized or file into different categories.
• Then we can name them based on these categories.
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…
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
Functional Groups
• Nature has done us a favor.
• There are many common groups that we can organize or file into different categories.
• Then we can name them based on these categories.
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…
Functional Groups
• Halogens• Alcohols• Ethers
• Aldehydes• Ketones
• Carboxylic Acids• Esters• Amines
• R-F, R-Cl, R-Br, • R-OH• R-O-R• R-COH• R-CO-R• R-COOH• R-COO-R• R-NH2
What the heck is R?
• The R represents a chain of carbon atoms.
• The the length of the chain is not significant.
• It is important to understand where the functional group lies in relation to the chain of carbon atoms
Halides
• Fluorides, Chlorides, Bromides, and Iodides
• Simply name the molecule as normal but add the prefix Fluoro, Chloro, Bromo, or Iodo as necessary
Halides
Cl
Cl
2, 3 dichlorohexane
I
I
3, 3 diiodo-1-pentene
Alcohols
• R-OH• Name like normal
except add an –ol suffix
Alcohols
OH
OHC
H
H
C
H
H
H
OH
2 propanol
ethanol
1butenol
Ethers
• R-O-R• Name two “R” groups
with –yl endings• End name in ether
Uses of Ethers
Common solvents.
General anesthetic
Ethers are slightly soluble in water.
Ethers
ODimethyl ether
O Ethyl methyl ether
Aldehyde
• R-COH• This is a carbon to
oxygen double bond with a hydrogen at the end.
• Name as normal except use a “-al” suffix
Al Who?Al Who?
Aldehydes
C
H
H
C
H
H
C
H
H
CH H
Obutanal
C
H
H
C
Cl
Cl
C
H
H
C H
O
C
H
H
H 3,3 dichloropentanal
Uses ofUses of AldehydesAldehydes• Formaldehyde H2CO is used in the production of:
Dollar BillsInk used in books, magazines, and newspapersWrinkle-Free ClothingGluesCar bumpers
KetonesKetones
• R-CO-R• This is a carbon to
oxygen double bond but in the center of a hydrocarbon chain rather than the end
• Name as normal but give it a “-one” suffix
Uses of KetonesUses of Ketones
• Ketones are often used as stabilizers in paints and perfumes. They prevent the other chemicals from degrading or breaking down.
• Acetone is found in nail polish remover.
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
Carboxylic Acids
• R-COOH or R-CO2H
• This is a carbon to oxygn double bond with the same carbon single-bonded to an OH group.
• Name as normal except give it the suffix “-anoic acid”.
HC
2 H3 O
2
Uses of Carboxylic AcidsUses of Carboxylic Acids
Carboxylic Acids are relatively weak acids.
Acetic Acid is the main ingredient in vinegar
Carboxylic Acids
C
H
H
C
H
H
C
H
H
CH OH
O
Butananoic acid
C
H
H
C
H
H
FC
O
HO 3-Fluoropropanoic acid
Esters
• R-COO-R• This is a carbon to oxygen
double bond with a carbon to oxygen single bonded to another single bonded carbon
• Name by given secondary branch “-yl” suffix and main branch “-anoate” suffix.
Esters
C
H
H
C
H
H
C
H
H
C
O
C
H
H
H C
H
H
HO
Secondary Branch
Main Branch
methylpentanoate
Methyl Pentanoate
Esters
C
H
H
H C
H
H
C
O
C
H
H
O C
H
H
HC
H
H
C
H
H
Butyl propanoate
C
H
H
H O
H
H
C
O
C
H
H
C C
H
H
HC
H
H
C
H
H
Methyl hexanoate
AminesAmines
• R-NH2
• Name the “R” group or groups with “-yl” endings
• Add the word “amine”
Amines
C
H
H
N
H
H
H Methyl amine
C
H
H
N
C
H
H
HH
H Dimethyl amine
Summary
ClR
Halide
OHRAlcohol
RR OEther
HR CAldehyde
O
RR CKetone
O
OHR CCarboxylic
Acid
O
OR CEster
O
R NH2RAmine
• 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”