CHEM 333 1nd Edition Lecture 6Outline of Last Lecture I. Review of hydrocarbonsII. NomenclatureIII. Physical propertiesIV. Uses and sources of alkanesV. Reactions of alkanesOutline of Current Lecture I. Conformational analysis II. Newman projection formula for ethaneIII. Newman projection formula for propaneIV. Newman projection formula for butaneCurrent LectureI. Conformational analysisConformational analysis deals with the shapes molecules make when they are rotated around singe bonds. For C2H6, we have two different shapes due to the rotation around the single bond between carbons. The rotamers here are conformers.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.II. Newman projection formula for ethaneAs we know ethane has an eclipsed and staggered isomer. In the eclipsed isomer there is 0 ˚ between hydrogen atoms looking from the view of a carbon atom. In the staggered isomer there is 60 ˚ between hydrogen atoms from the view of a carbon atom. (See below)Every hydrogen bond that eclipses is equal to +1 kcal/mol. Therefore the torsional strain is equalto 3 kcal/mol.III. Newman projection for propanePropane or CH3-CH2-CH3 will consist of 5 hydrogens and a methane when looking at the view from a carbon atom. The torsional strain for propane is 3.3 kcal/mol because there are two hydrogen bonds which each equal 1 kcal/mol and a hydrogen to methane bond which equals 1.3 kcal/mol. IV. Newman projection of butaneWhen analyzing butane we examine it from the bond between C2 and C3. Here we have eclipsed, staggered, gauche, and anti-conformation conformations.The dots represent CH3. As the CH3 molecules move farther apart the energy decreases while as they become totally eclipsed (the conformations on the ends) the energy is the
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