cyclohexane-lecture

Cyclohexane-lecture - Cyclohexane 1 Axial and Equatorial Positions of Cyclohexane Pink Axial Blue Equatorial 2 Cyclohexane Axial Positions More

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Unformatted text preview: Cyclohexane 1 Axial and Equatorial Positions of Cyclohexane Pink - Axial Blue - Equatorial 2 Cyclohexane Axial Positions More Crowded 1,3-diaxial interaction axial methyl H CH3 ring flip H H H H equatorial methyl H CH3 H H H H 1.8 kcal/mol more stable conformation 3 axial Methyl Cyclohexane 4 equatorial Methyl Cyclohexane 5 dimethylcyclohexane ax CH3 cis-1,2-dimethylcyclohexane 1 2 CH3 1 2 CH3 H CH3 1 2 CH3 2 H CH3 a x eq H H ring flip H 1 CH3 H same interactions in both conformations -equal in energy ax CH3 trans-1,2-dimethylcyclohexane 1 2 H CH3 eq ring flip ax CH3 2 1 CH3 eq CH eq 3 H lower in different interactions in both energy conformations -- NOT equal in energy 6 cis-1,2-dimethylcyclohexane 7 cis-1,2-dimethylcyclohexane 8 trans-1,2-dimethylcyclohexane 9 trans-1,2-dimethylcyclohexane 10 trans-1,2-dimethylcyclohexane 11 cis-1,3-dimethylcyclohexane cis-1,3-dimethylcyclohexane 1 ax CH3 CH3 H 3 CH3 trans-1,3-dimethylcyclohexane CH3 H 1 CH3 1 ring flip H 3 3 ax CH3 eq H3C 3 H different interactions in both conformations -- NOT equal in energy 1 CH3 H eq lower in energy ax CH3 ring flip 1 H 3 eq H3C H 3 ax CH3 1 CH3 eq H same interactions in both conformations -equal in energy 12 cis-1,3-dimethylcyclohexane 13 1,4-dimethylcyclohexane cis-1,4-dimethylcyclohexane 1 ax CH3 CH3 4 1 H3C eq H3C 4 H3C 4 H 1 CH3 eq same interactions in both conformations -- H equal in energy H ax CH3 CH3 1 H ring flip H 4 trans-1,4-dimethylcyclohexane 1 ax CH 3 4 ax CH3 H H ring flip H3C eq different interactions in both conformations -- NOT equal in energy 4 1 CH3 lower in energy eq H 14 1,4-dimethylcyclohexane cis-1-isopropyl-4-methylcyclohexane CH3 CH 1 4 H3C H3C ax CH3 CH ax CH 3 ring flip 1 CH3 4 H3C eq H CH3 4 H 1 CH H The larger group would prefer to be in the equatorial position -NOT equal in energy H lower in energy eq CH3 H Y 1,3-diaxial interaction Y kcal/mol strain Y kcal/mol strain -F 0.12 - CH3 0.9 - Cl 0.25 -CH2CH3 0.95 -Br 0.25 -CH(CH3)2 1.1 -OH 0.5 -C(CH3)3 2.7 15 Boat Conformations boat cyclohexane H H H H H H H H norbornane 16 Sugar Structure Glucose H H HO O OH H H OH H OH H OH HO HO HO H H OH H OH CH2OH 17 Polysaccharides Starch 18 Stereoids R CO2R O H R H R OR R H R 19 20 ...
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This note was uploaded on 12/06/2011 for the course CHEM 341 taught by Professor Sun during the Fall '08 term at ND State.

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