Naming organic compounds (rules of the IUPAC) Straight (continuous) chain hydrocarbons:

1. Naming organic compounds (rules of the IUPAC) • Straight (continuous) chain hydrocarbons: • A single path from one end C to the other end C • passes through every C atom without backtracking • This is called the normal form. • The letter n- precedes the name. • Most hydrocarbons so far have been this type. Ex. n-hexane Ex. n-hexane

2. B. Branched chain IUPAC rules: • The “parent name” is named after the longest • continuous chain of carbon atoms: Ex. Ex. hexane Parent name: because longest continuous carbon chain = 3 and the prefix is: propane Parent name: because longest continuous carbon chain = 6 and the prefix is: prop- hex-

3. The “first name” depends on: • a/ what is attached to the main chain; • b/ where it is attached; and, • c/ how many are attached • a/ What is Attached: • “Attachments” are called alkyl groups • They are alkanes with one less H atom: • Alkane Alkyl group • Name Formula Name Formula • methane CH4 methyl • ethane C2H6 ethyl • propane C3H8 propyl •  Rule: Replace –ane with –yl in name. CH3 C2H5 C3H7

4. How to picture the alkyl group attachments: Methane: methyl group: condensed: Ethane: ethyl group: condensed: Propane: propyl group: condensed: CH3 CH2CH3 CH2CH2CH3

5. Ex. Find the IUPAC name for isobutane: C4H10 Molecular formula: Condensed structural formula: CH3CHCH3CH3 parent name: longest continuous chain = so it is: 3 propane alkyl group: methyl IUPAC name: methyl propane

6. b/ Where the Alkyl Group is Attached: If there are > 3 carbon atoms, you must specify which carbon atom the alkyl group is attached to. This is done by numbering the carbon atoms in the longest chain from the end that will give the lowest number for the attached group. Ex. methyl group is attached at the number 2 carbon Use: 3 4 5 1 2 6 5 6 3 2 1 4 NOT: IUPAC name: 2-methyl hexane

7. Ex. H H parent name: alkyl group: position: IUPAC name: heptane methyl C H H 3 H 3-methyl heptane H H H H H H H H H H H H H Ex. C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H C parent name: alkyl group: position: IUPAC name: octane H methyl C H H 3 H 3-methyl octane

8. c/ A prefix is used to indicate the number of • attached groups there are of each type. • # of groups prefix: • 2 di- • 3 tri- • 4 tetra- • ETC • Ex. In: dimethyl triethylnonane, • di means 2 methyl groups • tri means 3 ethyl groups • nonane means a 9-C backbone • Then numbers are added as in the previous part • to specify exactly which C atom it is that each • of the methyl and ethyl groups are attached to.

9. Ex. What does 2,2,3-trimethyl pentane look like? pentane means start with a 5-C alkane backbone trimethyl means add 3 methyl groups 2,2,3 means place 2 methyls at the number 2 carbon and place 1 methyl at the number 3 carbon structural diagram: H H H H H C H C H H H C H C C H C C H H H H H C H H

10. If more than one type of alkyl group are attached, list them in alphabetical order in front of the parent name. Then put in the position numbers for each. Ex. Draw 3-ethyl-4-methylhexane parent: hexane alkyl groups: At position 3 put 1 ethyl At position 4 put 1 methyl H H C H H H H H H H H H H H H H H H C C C C C C C C H H H

11. Ex. What is the name of the compound below? H--C-----C-----C-----C-----C-----C-----C-----C-----C--H parent: alkyl groups: 2 _______, both at position __ 2 ________ at positions __ and __ start with parent: _______ add alkyls: _______ ______________ use prefixes: ________ _______________ IUPAC name: ______________________________ H C H H C H H H H H H H H H H H H H H H H H C C H H H C H H H H H C H H nonane 3 ethyls 5 methyls 1 nonane methylnonane ethyl dimethylnonane diethyl 3,3-diethyl-1,5-dimethylnonane