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Review Alkanes CnH2n+2 C4H10 CH3 (CH2) CH3 2
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Newman projections 1 2 3 4 1 2 3 4 staggered eclipsed stable
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Nomenclature heptane heptane heptane 3 branches 2 branches 4 branches
1 2 1 3 7 3 1 3 5 7 4 6 4 2 4 6 5 2 5 6 7 heptane heptane heptane 3 branches 2 branches 4 branches
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Nomenclature 3,5-diethyl -2-methyl -4-propyl heptane 2- methyl methyl
1 2 2- methyl methyl 3- ethyl 3 5 7 4 6 4- ethyl propyl propyl 5- ethyl 3,5-diethyl 3,5-diethyl -2-methyl -4-propyl heptane
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Cycloalkanes linear alkanes CnH2n+2 branched alkanes cycloalkanes
closed rings CnH2n 2 cyclo propane 3 1 bond angle = 60o tetrahedral angle = 109o very unstable
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Cycloalkanes cyclobutane bond angle = 88o tetrahedral angle = 109o
unstable
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Cycloalkanes cyclopentane bond angle = 108o tetrahedral angle = 109o
stable
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Cycloalkanes geometric isomers cis- 1,3- dichloro cyclo butane trans-
- - cis- 1,3- dichloro cyclo butane trans- 1,3- dichloro cyclo butane
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Cycloalkanes cyclohexane predicted bond angle = 120o
tetrahedral angle = 109o stable
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cyclohexane axial positions crowded only H equatorial positions
larger groups chair conformation boat conformation stable unstable
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cyclohexane cis- 1,2- dimethyl cyclo hexane
axial-equatorial trans- 1,2-dimethylcyclohexane trans-1,2-dimethylcyclohexane axial-axial equatorial-equatorial
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Optical isomerism 3-methyl hexane bromo chloro iodo methane bromo
Stereocenter 4 different substituents * * 3-methyl hexane bromo chloro iodo methane * * bromo cyclo pentane trans- 1,3-dibromo cyclopentane no C*
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Alkane Summary 1. Alkanes - sp3 hybridized 2. Relatively unreactive
Substitution with halogens Combustion 3. Non-polar IMF = London Dispersion Forces size structure
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4. Free rotation around C-C bonds
conformations 5. Non-cyclic alkanes - structural isomers 6. Cyclic alkanes - geometric isomers cis-, trans- 7. Alkanes - optical isomers stereocenters C*
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