Organic ChemistryOrganic Chemistry

Nomenclature: Nomenclature: AlkanesAlkanes

Summary: IUPAC Rules for Alkane Summary: IUPAC Rules for Alkane NomenclatureNomenclature

 1.1.   Find and name the longest continuous carbon chain.   Find and name the longest continuous carbon chain. This is called the This is called the parent chainparent chain. (Examples: methane, . (Examples: methane, propane, etc.)propane, etc.)

  2.2.   Number the chain consecutively, starting at the end   Number the chain consecutively, starting at the end nearest an attached group (nearest an attached group (substituentsubstituent). ).

  3.3.   Identify and name groups attached to this chain.   Identify and name groups attached to this chain.   4.4.   Designate the location of each substituent group with   Designate the location of each substituent group with

the number of the carbon parent chain on which the the number of the carbon parent chain on which the group is attached. Place a dash between numbers and group is attached. Place a dash between numbers and letters.  letters.  

5.5.   Assemble the name, listing groups in alphabetical   Assemble the name, listing groups in alphabetical order. order.     The prefixes di, tri, tetra etc., used to designate     The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered several groups of the same kind, are not considered when alphabetizing. Place a comma between multiple when alphabetizing. Place a comma between multiple numbers. (Example: 2,3-dimethylpropane)numbers. (Example: 2,3-dimethylpropane)

Step 1. Find the parent chain.Step 1. Find the parent chain.

• Where is the longest continuous chain of Where is the longest continuous chain of carbons?carbons?

Prefixes for # of CarbonsPrefixes for # of Carbons

11 MethMeth 66 HexHex

22 EthEth 77 HeptHept

33 PropProp 88 OctOct

44 ButBut 99 NonNon

55 PentPent 1010 DecDec

EndingsEndings

• Alkanes (all C-C single bonded parent Alkanes (all C-C single bonded parent chain) end in chain) end in –ane–ane– MethMethaneane CHCH44

– EthEthaneane CC22HH66

– PropPropaneane CC33HH88

• Attached carbon groups (substituents) end Attached carbon groups (substituents) end in in –yl–yl– MethMethylyl CH CH33 - -– EthEthylyl CHCH33CHCH22--– PropPropylyl CH CH33CHCH22CHCH2 2 –  –     

3-ethylpentane

Step 2. Number the parent chain.Step 2. Number the parent chain.• Number the parent chain so that the

attached groups are on the lowest numbers

1 2 3 4 5

Methyl is on carbon #2 of the parent chain

5 4 3 2 1

Methyl is on carbon #4 of the parent chain

GREEN is the right way for this one!

1 2

3 7 8

4 5 6

8 7

6 2 1

5 4 3

Groups on 2, 3, and 5Groups on 4, 6, and 7

1 2 3 4 5 6

7Groups on 2 and 5

7 6 5 4 3 2 1

Groups on 3 and 6

Step 3. Name the attached groups.Step 3. Name the attached groups.

• Carbon (alkCarbon (alkylyl) groups) groups– MethMethylyl CH CH33 - -

– EthEthylyl CHCH33CHCH22--

– PropPropylyl CH CH33CHCH22CHCH2 2 ––

Step 4. Designate where the group Step 4. Designate where the group is attached to the parent chain.is attached to the parent chain.

• Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain.

1 2 3 4 5

2-methyl

Step 5. Alphabetize the groups, Step 5. Alphabetize the groups, combine like groups, and assemble.combine like groups, and assemble.

• The prefixes di, tri, tetra The prefixes di, tri, tetra etc., used to designate etc., used to designate several groups of the several groups of the same kindsame kind

• Prefixes are not Prefixes are not considered when considered when alphabetizing (Example: alphabetizing (Example: dimethyl = m for dimethyl = m for alphabetizing)alphabetizing)

• Parent chain goes LASTParent chain goes LAST

Draw Some Simple AlkanesDraw Some Simple Alkanes

• 2-methylpentane2-methylpentane

• 3-ethylhexane3-ethylhexane

• 2,2-dimethylbutane2,2-dimethylbutane

• 2,3-dimethylbutane2,3-dimethylbutane

Structural FormulasStructural Formulas

• “Lazy” way to write the Hydrogens• Instead of drawing the bonds, just state

how many hydrogens are attached• NOTE: The bonds are between

CARBONS in a parent chain, and not hydrogens!

Structural FormulaLewis Structure

IsomersIsomers

• Straight chain alkanes:Straight chain alkanes: An alkane that An alkane that has all its carbons connected in a row.has all its carbons connected in a row.• Branched chain alkanes:Branched chain alkanes: An alkane An alkane that has a branching connection of that has a branching connection of carbons.carbons.• Isomers: Isomers: Compounds with same Compounds with same molecular formula but different molecular formula but different structures.structures.

AlkanesAlkanes

Example:Example: Name the following compounds: Name the following compounds:

CH3 CH CH CH2 CH CH3

CH2CH3C

CHCH3

CH3

CH3

CH3

CH3

AlkanesAlkanesExample: Write the condensed structure for Example: Write the condensed structure for the following compounds:the following compounds:

3,3-dimethylpentane3,3-dimethylpentane

2-methyl-4-sec-butyloctane2-methyl-4-sec-butyloctane

1,2-dichloro-3-methylheptane1,2-dichloro-3-methylheptane