Organic Naming Rules Chem 332 For complete Rules go to: http://www.acdlabs.com/iupac/nomenclature/

Organic Compounds Carbon Hydrogen Oxygen Nitrogen 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 Does anyone know the prefixes beyond ten?

C4H10 C4H10 Isomers Different Structure Same Formula If that’s not enough, how about this one: C H Different Structure Same Formula C H Formula? Formula? Definition: Isomer- chemicals that have the same formula but different structures 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!

So what to do? Number of hydrogens is going to be the same, regardless of isomerism C H C H C H 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 The number of hydrogens will change later but for right now with only single bonds, they will always be the same. What is the equation for C & H in an alkane? CnH2n+2

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 Note the differences between this list and the covalent prefixes. Only the first four are diffferent.

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

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 C4H10 Butane But how do we deal with branches? C 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

Methyl Propane Example methyl propane Branch is one long Longest unbranched chain of carbons is three long propane Methyl Propane

Practice C H Methyl butane H C Ethyl pentane

One More Practice Methyl Butane It doesn’t matter which way you go! (Provided you correctly pick the longest unbranched chain) You can turn corners, go up, down, left, right, zig-zag, or do what ever you want provided you don’t double back on yourself. C

Methyl Hexane Be Careful Methyl Hexane C This is your longest uninterrupted chain Hexane Remember that molecules don’t care about left or right, top or bottom. Methyl Hexane

A Small Wrinkle Methyl Pentane Methyl Pentane C Methyl Pentane H C 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 2- 3- So… Methyl Pentane Methyl Pentane C C Here the methyl group is on the second carbon from the end Here the methyl group is on the third carbon from the end Again, the molecule on the left is 2-methyl pentane NOT 4-methyl pentane. Molecules don’t care about left or right so we start numbering from the closest side. So…

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 2-methyl heptane H C 4-methyl octane H C 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

2,2 dimethyl heptane Practice 2- methyl heptane 2- methyl 2-methyl, 2-methyl heptane Sounds redundant 2,2 dimethyl heptane

More Practice 2, 6-dimethyl octane 3 ethyl-2,4-dimethyl pentane C C H Technically you should but branches in alphabetical order but I won’t be that picky. 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 C2H6 C2H4 Ethane- notice that each carbon has four bonds What will happen to the structure if we double bond the two carbons? Different structures need different names C2H4 C H 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 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

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. Alkenes are molecules with double bonds Alkynes are molecules with triple bonds Alkanes are molecules only with single bonds

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

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

Prefixes for #’s of groups Prefixes for #’s of CARBONS Suffixes Single Double Triple -ane -ene -yne 1- 2- 3- 4- 5- 6- 7- 8- 9- 10- Mono Di Tri Tetra Penta Hexa Hepta Octa Nona Deca 1- 2- 3- 4- 5- 6- 7- 8- 9- 10- Meth Eth Prop But Penta Hexa Hepta Octa Nona Deca Branches use -yl Circles use Cyclo- Identify the longest chain (it must contain the double or triple bond if present) Name it as normal If Double or triple bonds are present use the correct suffix and identify the starting position with a number Identify the branches Name any branches by using carbon prefixes and –yl suffixes and identify their positions with a number Add a prefix to indicate multiple branches using the groups prefixes

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 Keep 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. Each end and each “point” represents a carbon atom. The hydrogen atoms are assumed to be there. So lets now ignore the hydrogens completely!

Is it that easy? H C C H

One More C 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? Multiple bonds, rings, other atoms

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 Note that a number is not needed on the first example. Note that numbers are now needed to indicate position. It doesn’t matter, though which is 1 and which is 2 1,2 dimethyl cyclohexane

Try These 1 ethyl, 3 methyl cyclobutane 1 propyl, 3 methyl cylclohexane

How about in Shorthand? 2 pentene 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 2, 3 dichlorohexane I 3, 3 diiodo-1-pentene

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

Alcohols OH OH 2 propanol 1butenol OH C H ethanol

Ethers R-O-R Name two “R” groups with –yl endings End name in ether

Ethers are slightly soluble in water. Uses of Ethers Common solvents. General anesthetic Ethers are slightly soluble in water.

Ethers O Dimethyl 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?

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

Uses of Aldehydes 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.

Ketones C H O propanone C H O 2 hexanone

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”. HC2H3O2

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

Carboxylic Acids Butananoic acid 3-Fluoropropanoic acid C H OH O C H F

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

Esters C H O Butyl propanoate C H O Methyl hexanoate

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

Amines C H N Methyl amine C H N Dimethyl amine

Summary Cl R Halide OH R Alcohol R O Ether H R C Aldehyde O R C Ketone Carboxylic Acid O O R C Ester NH2 R Amine

Summary - “-ane” Alkanes Alkenes Alkynes Halides Alcohols Ethers Aldehydes Ketones Carboxylic Acids Esters Amines - “-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”