Embed Size (px)
DESCRIPTION
Naming Hydrocarbons (nomenclature). What is a Hydrocarbon?. A hydrocarbon is an organic molecule composed of carbon and hydrogen (duh). There are 3 main classes of hydrocarbons - PowerPoint PPT Presentation
Citation preview
Naming Hydrocarbons (nomenclature)
What is a Hydrocarbon?• A hydrocarbon is an organic molecule composed of
carbon and hydrogen (duh).• There are 3 main classes of hydrocarbons
– Alkanes: Since there are only single bonds throughout these molecules, they are referred to as saturated hydrocarbons. The general formula of an alkane is CnH2n + 2.
– Alkenes: An alkene has at least one double bond. It will have 2 less hydrogens (than a comparable alkane) for each double bond.
– Alkynes: An alkyne has at least one triple bond. It will have 4 less hydrogens (than a comparable alkane) for each triple bond.
Basic Naming of Hydrocarbons
Hydrocarbon names are based on: a) type, b) # of carbons, c) side chain type and position
1) The name will end in: -ane for alkanes, -ene for alkenes, or -yne for alkynes
2) the number of carbons is given by a “prefix”
1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec-
Naming straight chains
What names would be given to these:C7H16
C9H20
C2H2
C4H6
CH2
C3H6
heptane nonaneethynebutynemethenepropene
Mnemonic for First Four Prefixes
First four prefixes• Meth-
• Eth-
• Prop-
• But-
Monkeys
Eat
Peeled
Bananas
?Decade
Decimal
Decathalon
Other Prefixes
• Pent-
• Oct-
• Dec-
• Hex-, Hept-, Non-
Drawing Structures: It’s All Good
CH3
CH
CH
CH3
CH3
CH3
CH3
CHCH
CH3
2-butene
This is called the “condensed structure”
C C C C
H
H
H
H H H
H
H
CH3 CH CH CH3
On a test, choose a method that shows all HsCH3CH=CHCH3
Using brackets can also shorten some formulas: CH3CH2CH2CH2CH2CH3 vs. CH3(CH2)4CH3
Numbering CarbonsQ- draw penteneA- Where’s the double
bond? We # C atoms.
• Naming compounds with multiple bonds is more complex than previously indicated.
• When 2+ possibilities exist, #s are needed.• Always give double bond the lowest number.• Q - Name these
C C C CCH3
H
H
H
H H H
HCH31
C2
C3
C4
C5
H
H
H
H H H
HCH35
C4
C3
C2
C1
H
H
H
H H H
H
ethene
3-nonyne
2-buteneCH3
CH
CH
CH3
CH3 CH3
C2H4
1-pentene
CH3 CH3
CH3
CH3Naming Side Chains• The names of molecules with
branches are based on: side chains, root
• The “root” or “parent chain” is usually the longest possible hydrocarbon chain.
• The root must include multiple bonds if they are present. If a cyclic structure is present it will be the root even if it is not the longest chain.
• Side chains are also called “side branches” or “alkyl groups”. Their names end in -yl.
Common side chains :-CH3 methyl, -CH2CH3 ethyl, -CH2CH2CH3 propyl
2,3-dimethylpentane
CH3 CH3
CH3
CH3
IUPAC Rules for Naming Hydrocarbons1. Choose the correct ending: -ane, -ene, or -yne2. Determine the longest carbon chain. Where a
double or triple bond is present, choose the longest chain that includes this bond. If there is a cyclic structure present, the longest chain starts and stops within the cyclic structure.
3. Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest #. Carbons in a multiple bond must be numbered consecutively.
4. Attach a prefix that corresponds to the number of carbons in the parent chain. Add cyclo- to the prefix if it is a cyclic structure.
5. Determine the correct name for each branch (“alkyl” groups include methyl, ethyl, propyl, etc.)
6. Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane)
7. When two or more branches are identical, use prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane). Numbers are separated with commas. Prefixes are ignored when determining alphabetical order. (e.g. 2,3,5-trimethyl-4-propylheptane)
8. When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)
IUPAC Rules for Naming Hydrocarbons
ene
Naming Side ChainsExample: use the rules on this handout to
name the following structure
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
Rule 1: choose the correct ending
ene
Rule 2: determine the longest carbon chain
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
Naming Side Chains
Rule 3: Assign numbers to each carbon
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
ene
Naming Side Chains
Rule 3: Assign numbers to each carbon
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
ene
Naming Side Chains
1-hexene ene
Rule 4: attach prefix (according to # of Cs)
Naming Side Chains
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
Rule 5: Determine name for side chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
1-hexene 1-hexene
ethyl
methyl
methyl
Naming Side Chains
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
1-hexene2-ethyl-4-methyl-4-methyl-1-hexene
ethyl
methyl
methylRule 6: attach name of branches alphabetically
Naming Side Chains
Rule 7,8: group similar branches
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
1-hexene2-ethyl-4-methyl-4-methyl-1-hexene
ethyl
methyl
methyl
Naming Side Chains
Rule 7,8: group similar branches
CH3 CH2 C
CH2
CH2 C
CH2
CH3
CH3
CH3
CH3 CH2 C2
CH21
CH23
C4
CH25
CH3
CH3
CH36
2-ethyl-4,4-dimethyl-1-hexene
ethyl
methyl
methyl
Naming Side Chains
Page 547-8 Questions 3, 5
CH3 CH CH2
CH3 CH CH CH3
CH3 CH CH C
CH3 CH3
CH3
CH C CH2 CH3
2-butene
propene
1-butyne
CH3 CH CH2
CH3 CH CH CH3
CH3 CH CH C
CH3 CH3
CH3
2,4-dimethyl-2-pentene
CH C CH2 CH3
CH2 CH C CH2 CH3
CH3
CH3
CH3 C CH CH2
CH3
CH2 CH3
CH CH CH2
CH2 CH3
CC
CH3CH3
CH3
For more lessons, visit www.chalkbored.com
b) same
c) 5-ethyl-4-methyl-2-heptyne
a) 3,3-dimethyl-1-pentene
CH2 CH C CH2 CH3
CH3
CH3
CH3 C CH CH2
CH3
CH2 CH3
CH CH CH2
CH2 CH3
CC
CH3CH3
CH3
For more lessons, visit www.chalkbored.com
