Organic Naming Rules

Chemistry 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?

• That wasn’t so bad, right?

• 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

• Meth• Eth• Prop• But• Pent• Hex• Hept• Oct• Non• Dec

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

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

Multiple Bonds

• Carbon can make multiple bonds with 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!!

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

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

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

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

AlcoholsOH

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 Bills

Ink used in books, magazines, and newspapers

Wrinkle-Free Clothing

Glues

Car 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 oxygen 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.

EstersEsters

Many esters have distinctive fruit-like odors, which has led to their common use in artificial flavorings and fragrances.

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”

Uses of Amines

• Amines are found in many pharmaceuticals

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”

Can You Do This?

• YES!

• It takes:

• Memorization

• Practice

• Practice

• Practice

• Practice

• And, oh yes…

• Practice!