The Alkanes Ch 4

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The Alkanes (Ch 4)

• - Hydrocarbons (binary compounds composed of C
  and H only)
• T he stability of C-C bond with respect to the
  C-H bond makes possible
• the formation of long chains
• Single bond only (sp3) alkane
• At least one double bond (sp2) alkene
• At least one triple bond (sp) alkyne

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Functional groups
Alkane Alkyl group Abbr. CH4
(methane) CH3- (methyl) Me- CH3CH3
(ethane) CH3CH2- (ethyl) Et- CH3CH2CH3
(propane) CH3CH2CH2- (propyl) Pr- CH3CH2CH3
(propane) CH3CHCH3 (isopropyl) i-Pr-
R
(phenyl) Ph-
benzene
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Alkyl Halides (Haloalkanes)
primary
secondary
tertiary
4
Alcohols
Or more simply R-OH
CH3CH3 CH3CH2 CH3CH2OH
Ethane ethyl ethyl alcohol
Primary secondary tertiary
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Other Functional Groups Ethers Amines Aldeh
ydes and Ketones Carboxylic acids (and
derivatives) Nitriles
(R alkyl,H)
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Chemistry of Alkanes
Source petroleum distillation, refining and
thermal cracking Shape C-C single bonds, sp3
hybrids, zigzag chains
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Isomerism
C6H14
Chain length C4 C5 C6 C7 C8 C9
C10 of isomers 2 3 5 9
18 35 75
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Alkane nomenclature
Methane C1 Ethane C2 Propane C3 Butane C4 Pentan
e C5 Hexane C6 Heptane C7 Octane C8 Nonane C9
Decane C10 Undecane C11 Dodecane C12 Tridecane
C13 Tetradecane C14 Etc.
Linear alkanes
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What about branched alkanes? (IUPAC)
Rule 1
Locate the longest chain and name it accordingly
CH3CH2CH2CH2CH2CH3
(hexane)
CH3
substituents
CH3CH2CH2CH2CHCH3
(heptane)
CH2
CH3
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Rule 2 Number the longest chain beginning
with the end nearer the substituent (the
heavier if more than one)
1
6 5 4 3 2
7 6 5 4 3
CH3CH2CH2CH2CHCH3
CH3CH2CH2CH2CHCH3
CH3
2
CH2
1
CH3
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What about branched alkanes?
Rule 3 Use the for locating the
substituents
1
6 5 4 3 2
7 6 5 4 3
CH3CH2CH2CH2CHCH3
CH3CH2CH2CH2CHCH3
CH3
2
CH2
2-methylhexane
1
CH3
3-methylheptane
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What about branched alkanes?
Rule 4 when 2 or more subs. are present, give
each subst a corresponding to its location
on the longest chain
CH3CH-CH2-CHCH2CH3
CH3
CH2
4-ethyl-2-methylhexane
CH3
Alphabetical order
NOT 3-ethyl-5-methylhexane
(first point of branching must have smaller )
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Rule 5 When two subs are present on the same
C atom, use that twice
CH3
CH3CH2 C CH2CH2CH3
CH2CH3
3-ethyl-3-methylhexane
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Rule 6
When two or more subs are identical use the greek
suffix di-, tri-, tetra-, etc.
CH3
CH3
CH3
CH3CH CHCH3 CH3CHCHCHCH3
CH3CCH2CCH3
CH3
CH3
CH3
CH3
CH3
CH3
2,3-dimethylbutane 2,3,4-trimethylpentane
2,2,4,4,-tetramethylpentane
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Rule 7
When there are two chains of equal length,
choose as the main the chain with the greater
of subs.
7 6 5 4 3 2 1
CH3CH2 CH CH CH CH CH3
CH3 CH2 CH3 CH3
CH2
CH3
2,3,5-trimethyl-4-propylheptane
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Rule 8
When branching occurs at an equal distance from
either end of the longest chain, choose the name
that gives the lower at the first point of
difference
First point of difference
6 5 4 3 2 1
CH3 CH CH2 CH CH CH3
CH3 CH3 CH3
2,3,5-trimethylhexane and NOT 2,4,5-trimethylhex
ane
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Some  common  names
CH3
CH3 C CH2-
CH3CH2CH2- Propyl or n-propyl CH3CHCH3
1-methylethyl or isopropyl
CH3
Neo-pentyl
CH3CH2CH2CH2 - n-butyl CH3CH2CHCH3
sec-butyl CH3CHCH2-
iso-butyl CH3 C CH3
tert-butyl
CH3CH2CH2CHCH2CH2CH3
CH-CH3
CH3
CH3
CH3
4-isopropylheptane or 4-(1-methylethyl)heptane
CH3
CH3
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Classification of H atoms
CH3
CH3 CH CH2 CH3
primary secondary tertiary
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Alkyl halides
CH3CH2Cl CH3CH2CH2F
CH3CHBrCH3 Chloroethane 1-fluropropane
2-bromopropane The substituent closer to the end
(either X or R alphabetical order counts)
determines the chain numbering.
CH3
CH3
CH3CHCHCH2CH3
CH3CHCH2CHCH3
2-chloro-3-methylpentane
2-chloro-4-methylpentane
Cl
Cl
Also  common  names Ethyl chloride, isopropyl
bromide, tert-butyl chloride, isobutyl chloride,
etc.
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Alcohols (nomenclature)
Add the suffix ol to the IUPAC name
CH3CH2CHCH2CH2CH2OH
CH3
4-methyl-1-hexanol or more preferably
4-methyl-hexan-1-ol
Thus - Select the longest chain to which
the OH is attached - Number the chain to give
the OH the lowest
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A few examples
CH3CHCH2CH2CH2OH
CH3CH2CH2OH CH3CHCH2CH3
CH3
OH
1-propanol 2-butanol
4-methyl-1-pentanol
CH3
ClCH2CH2CH2OH
CH3CHCH2CCH3
OH CH3
3-chloro-1-propanol
4,4-dimethyl-2-pentanol
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Cycloalkanes
Cyclopropane Cyclopentane Cyclohexane