CHEM 3331 1nd Edition Lecture 16Outline of Last Lecture I. E1 reactionII. Zaitsev’s RuleIII. E2 reactionIV. StereochemistryV. E1 vs. E2 vs. Sn1 vs. Sn2Outline of Current Lecture I. AlkenesII. Elements of unsaturationIII. NomenclatureIV. UsesV. StabilityVI. Physical propertiesCurrent LectureI. AlkenesAlkenes are also called olefins. The simplest alkene is ethane. In alkenes there is a double bond formed between two carbon atoms. One is a preexisting sigma bond and the other is a newly formed pi bond. Pi bonds are weaker than sigma bonds. There is no free rotation around the double bond. Therefore, we would have to break the pi bond to establish rotation around th single sigma bond.II. Elements of UnsaturationBy using combustion analysis we can view products to determine how much carbon and hydrogen are in our reactant. For example, if we determine a compound is C6H12 we can 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.determine it is either cyclohexane or hexane. Elements of Unsaturation will be abbreviated to EoU. An EoU equal to 1 indicates either a ring or a double bond.The equation for determining our EoU number is 2n(c)+2-n(h)/2. Here n(c) stands for the number of carbons in our compound and n(h) stands for the number of hydrogens. For our example compound EoU= 2(4)+2-6/2=4/2=2. This means we can have two rings, two double bonds, a double bond and a ring, or a triple bond. If our compound contains oxygen it can simply be ignored in the equation. If we have a halogen we expect one less hydrogen. If we havenitrogen we can expect one more hydrogen.III. NomenclatureThe nomenclature for alkenes is similar to that for alkanes. To begin there can be an insertion of –yl- in ethane, butane, and propene.1) the longest chain must contain the double bond.2) number the chain so that the double bond gets the lowest number.3) substituents are secondary to double bondE-Z notation is equated to cis-trans relationship. Choose the higher priority on the left and right side of the molecule. If they reside on the same side (both top, both bottom) then they are E (cis) if they are opposite it is Z (trans).A molecule with two double bonds contains a diene at the end of its name. a molecule with three has triene, and so on. For example, 1,3,5- heptatriene. Vinyl is a small carbon based compound with a double bond. An allyl is a larger carbon based compound with a double bond. IV. UsesUses are commonly related to the reactivity of alkenesEthylene is found in oil or natural gas.Ethylene oxide is transformed to ethylene glycol (antifreeze).The production of ethanol for alcoholic beverages commonly through fermentation.It can be used to produce vinyl chloride which is transformed to PVC (pipes and plumbing).It can be used to produce polyethylene (plastic).Propene can be transformed to propylene glycol and propylene oxide which are commonly usedin cosmetics.It can also be turned into polypropylene (polymer).Isopropyl alcohol (rubbing alcohol) can be transformed to acetone (solvent).A polymer is a long strand of a repeated monomer that break the double bond and create two new bonds with the next monomer strand to be attached.V. StabilityTrans isomers are more stable than cis isomers. Trans have a lower heat of combustion than cis. They also have a lower heat of hydrogenation. Hydrogenation is the most commonly used method. With a double bond the strain on the angles is increased. Unless it is a large enough molecule, such as decene. VI. Physical PropertiesCsp2= s +2p 33% sCsp3= s +3p  25% sS has its highest density at the nucleus. P has no density at the nucleus. Csp2 is more electronegative than Csp3.Cis alkenes are more polar and trans alkenes depending on the substituents will have a polarity close to zero. This also causes a difference in their boiling