CH 221 1st Edition Lecture 14 Outline of Last Lecture I. Plane Polarized LightII. Enantiomeric ExcessIII. Compounds with Two Asymmetric CentersIV. DiastereomersOutline of Current Lecture V. Two Asymmetric Centers: Three StereoisomersVI. Meso CompoundsVII. Asymmetric Center versus StereocenterVIII. Cis-Trans IsomersIX. Introduction to AlkenesCurrent LectureV. Two asymmetric centers in three stereoisomers includes a meso compound and a pair of enantiomers.Ex. 2,3-dibromobutaneFischer projections are also used to demonstrate asymmetry.VI. Meso compounds have a plane of symmetry and have superimposable mirror images.- They are optically inactive even with asymmetric centers- Ex. (2R,3S)-3-bromobutan-2-ol- For cyclic compounds with the same substituented bonded to two asymmetric centers- Cis- a meso compound- Trans- pair of enantiomers- Each isomer has two chair conformers- Rings can be trans-fused or cis-fused- Nitrogen and Phosphorus can also be asymmetric centersVII. An asymmetric center has an atom attached to four different groups.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Stereocenter- an atom at which the interchange of two groups produces a stereoisomer.VIII. Cis-Trans Isomers- result from restricted rotation- Cyclic structures restrict rotation- Cis- substituents on same side of ring- Trans- substituents on opposite sides of ring- Ex. Cis-1-bromo-3-chlorocyclobutane, trans-1-bromo-2-methylcyclopentane- Cis-stereoisomers are a pair of enantiomers- Trans-stereoisomers are a pair of enantiomersIX. Alkenes have a molecular formula= CnH2 n+n - There are two hydrogens for every π bond or ring- Degree of unsaturation= total number of π bonds and rings-C8H18 has two degrees of unsaturation- Compounds with six hydrogen have two degrees of unsaturation- Saturated hydrocarbons have no double bonds- Unsaturated hydrocarbons have one or more double bonds- Replace “ane” of alkanes with “ene” to name alkenes- Functional group gets lowest possible number- Ex.
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