CHEM 2211 1st Edition Lecture 7 Outline of Current Lecture I II III Ring flip with two substituents on a cyclohexane Fused cyclohexane rings Functional groups Vocabulary Cis isomer Conjugated alkene Carboxyl group Trans isomer Cycloalkane Aldehyde Geometric isomer Arene Ketone 1 3 diaxial interactions Alkyne Carboxylic acid Fused ring Alcohol Ester Alkane Alkyl halide Acid halide Alkene Ether Amide Isolated alkene Amines Current Lecture I Ring Flip with two substituents on a cyclohexane A To predict which conformer is more stable we must determine where the substituents are B A cis isomer is an isomer with both groups on the same side as the ring C A trans isomer is an isomer with one group on one side and the other group on the other side of the cyclohexane D These are examples of geometric isomers molecules with the same configuration and the same bonds but different spatial arrangements Cis 1 4 dimethylcyclohexane Trans 1 4 dimethylcyclohexane E Remember that in order for a molecule to be a cis isomer the substituents must be on the same side of the ring Cis isomer Trans isomer F Cis isomer stability vs trans isomer stability in 1 4 dimethylcyclohexane i Because one methyl group is in the equatorial position and the other on the axial position each isomer is equally stable ii The trans isomer is a different story The conformer with the equatorial substituents is the most stable iii The reason the equatorial trans isomer is more stable is because the axial trans isomer has four 1 3 diaxial interactions 1 1 3 diaxial interactions generic term for the interactions between molecules in the same plane II Fused cyclohexane rings A A fused ring shares two carbons with another ring Because of this fact cis fused rings are less stable than trans fused rings Trans fused rings Cis fused rings III Functional Groups A Alkanes B Alkenes i Isolated alkenes Single isolated alkene Double isolated alkene ii Conjugated alkenes iii Cycloalkenes C Arene aka Benzene i An alkene with alternating double bonds D Alkyne i Skeleton model should look like this The carbon to carbon triple bond must have a 180 angle E Alcohol When the functional group is circled the carbon that it s attached to must also be circled F Alkyl Halides X stands for any halogen G Ether Ethers are an oxygen bonded to one or two different groups Note that both of the carbons the oxygen is attached to are circled H Amines Primary secondary tertiary and quaternary Amines I Carbonyl Group Generic carbonyl group where Y O H R X Aldehyde Ester Ketone Acid Halide Carboxylic Acid Amide
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