Organic Naming Rules

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

H H C H H H H H H H H C C C C H H C C C H H H H H H H H Isomers • If that’s not enough, how about this one: Different Structure Same Formula Formula? Formula? C4H10 C4H10

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!

H H H C H H C H H H H H H H H H H H H C C C C C H H C C C H H C C C C H H H H H H H H H H H H C H H H So what to do? • Number of hydrogens is going to be the same, regardless of isomerism C5H12 C5H12 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

1 2 3 4 5 6 7 8 9 10 Meth Eth Prop But Pent Hex Hept Oct Non Dec Name based on number of Carbons

H H C H H H H H C C H H H H H H H H H H H H C C C C C C C C H H H H H H H H H Did that Really Help? CH4 Carbon tetrahydride becomes: Methane C2H6 Dicarbon hexahydride becomes: Ethane C8H18 Octacarbon ???hydride becomes: Octane

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?

H H H C C H H H H H H C C H Examine Structures C2H6 Ethane- notice that each carbon has four bonds What will happen to the structure if we double bond the two carbons? C2H4 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.

H H H C C H H C C H H H H H H C C H So…. C2H6 C2H2 C2H4 ethane ethyne ethene

Alkenes • Alkenes contain adouble bondin the molecule. • The general formula for alkenes is CnH2n

A 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! • 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

H C H H H H H H H H H H C C C C C C C H H H H H C C C C C H H H H H H H H H H H H H H C C C C H H H H Practice 2-heptene 1-butene 3 methyl-1-pentene

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…

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 Functional Groups

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

Cl Cl I I Halides 2, 3 dichlorohexane 3, 3 diiodo-1-pentene

Alcohols • R-OH • Name like normal except add an –ol suffix

OH OH H H OH H C C H H Alcohols 2 propanol 1butenol ethanol

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.

O O Ethers Dimethylether Ethyl methylether

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?

O H H H H C C C C H H H H O H H Cl H H C C C C C H H H Cl H Aldehydes butanal 3,3 dichloropentanal

Uses ofAldehydes • Formaldehyde H2CO is used in the production of: Dollar Bills Ink used in books, magazines, and newspapers Wrinkle-Free Clothing Glues Car bumpers

Ketones • 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 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.

O H H H C C C H H H O H H H H H H C C C C C C H H H H H H Ketones propanone 2 hexanone

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”. HC2H3O2

Uses of Carboxylic Acids Carboxylic Acidsare relatively weak acids. Acetic Acid is the main ingredient in vinegar

O H H H H C C C C OH H H H O H H HO C C C F H H Carboxylic Acids Butananoic acid 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 Many esters have distinctive fruit-like odors, which has led to their common use in artificial flavorings and fragrances.

Secondary Branch Main Branch O H H H H H H C C C C C O C H H H H H H Esters methyl pentanoate Methyl Pentanoate

O H H H H H H H C C C O C C C C H H H H H H H O H H H H H H H C O C C C C C C H H H H H H H Esters Butylpropanoate Methylhexanoate

Amines • R-NH2 • Name the “R” group or groups with “-yl” endings • Add the word “amine”

Organic Naming Rules