1. Alkanes - Isomerism
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2. Nomenclature
Organic nomenclature is based on a class of compounds known as alkanes
Contain only carbon and hydrogen
All carbon atoms are sp3 hybridized
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3. Nomenclature
International Union of Pure and Applied Chemistry (IUPAC) has established the system
We will refer to names derived from this system as systematic nomenclature or IUPAC nomenclature (shown in blue)
Additional names such as isopentane and neopentane are common names (shown in red)
A compound may have more than one name BUT a name must specify only one compound
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4. Nomenclature
Typically any unspecified alkyl group is represented as R-
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5. Nomenclature
Alkyl substituent group names are combined as needed with the alkane name for the longest continuous straight chain to constitute a compound name
Note that these compounds all have the formula C7H16; they are isomers
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6. IUPAC Systematic Nomenclature - Alkanes
Determine longest continuous chain (i.e. parent hydrocarbon)
Cite the name of substituent before the name of the parent hydrocarbon along with the number of the carbon to which it is attached
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7. IUPAC Systematic Nomenclature - Alkanes
Number in the direction that gives the lower number for the lowest-numbered substituent. Substituents are listed in alphabetical order – neglecting prefixes such as di- tri- tert- etc.
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8. IUPAC Systematic Nomenclature - Alkanes
When both directions yield the same lower number for the lowest numbered substituent, select the direction that yields the lower number for the next lowest numbered substituent
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9. IUPAC Systematic Nomenclature - Alkanes
If same substituent numbers are obtained in either direction, number in direction giving lowest number to the first named substituent
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10. IUPAC Systematic Nomenclature - Alkanes
If compound has two or more chains of the same length, parent hydrocarbon is chain with greatest number of substituents
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11. IUPAC Systematic Nomenclature - Alkanes
Names such as sec-butyl and tert-butyl are acceptable, but systematic substituent names are preferable
Numbering of the substituent begins with the carbon attached to the parent hydrocarbon
This number together with the substituent name is placed inside parentheses
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12. Alkyl Nomenclature
A primary carbon is one that is bonded to only one other carbon, frequently represented by 1
A primary hydrogen is attached to a primary carbon
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13. Alkyl Nomenclature
A secondary carbon is one that is bonded to two other carbons, represented by 2, also by sec- or s-
A secondary hydrogen is attached to a secondary carbon
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14. Alkyl Nomenclature
A tertiary carbon is one that is bonded to three other carbons, represented by 3, also by tert- or t-
A tertiary hydrogen is attached to a tertiary carbon
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15. Alkyl Nomenclature
Reactivity often depends on whether a carbon or hydrogen is 1, 2, or 3
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16. Nomenclature of Cycloalkanes
Cycloalkanes generally are shown as skeletal structures
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17. Nomenclature of Cycloalkanes
Ring is the parent hydrocarbon unless the alkyl substituent has more carbons; in that case the substituent becomes the parent hydrocarbon
If only one substituent, no need to give it a number
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18. Nomenclature of Cycloalkanes
If the ring has 2 substituents, list in alphabetical order and give number 1 to first named group
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19. Nomenclature of Cycloalkanes
If there is more than one substituent, list in alphabetical order; one substituent is given the position number 1; number either clockwise or counterclockwise - lowest numbers
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