CHEM 2211 1nd Edition Lecture 17 Outline of Last Lecture I Chapter 5 Alkenes Outline of Current Lecture I Clicker questions II Chapter 6 Alkene reactions Cl Current Lecture 1 Clicker Questions Assign R S or E Z where appropriate and name the following molecule Rules for numbering Remember that alkene group needs to have the lowest possible number But also look at the other substituents With this in mind we can number the cycloalkene going clockwise with 1 on the alkene and the most substituents and 6 on the Chlorine So name is 6 Chloro 1 Methylcyclohexene Now to assign R and S or E and Z if we can E and Z can not be assign in rings smaller than 8 so we look if there are any sterocenters to assign R or S to The 6th Carbon has 4 different groups off of it so it can be assigned either R or S Cl is 1st priority the alkene to the right is 2nd priority the C to the left is 3rd and the H off the bottom is 4th The priority goes clockwise so the 6th carbon is assign the letter R 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 Since there is only one sterocenter R can go in front of the of name without the number carbon it assigns Final name R 6 Chloro 1Metylcyclohexene Chapter 6 Stability of Alkenes Most stable alkenes have four R groups R groups start with C Most stable Tetra sub tri sub di sub mono sub least stable In between tri and di sub there are two more stabilities cis and trans of di Trans is more stable than cis Both cis an trans are more stable than di sub with both subs coming off one carbon Stability is measured by energy Less energy is more stable Meaning stable conformations exist in the valleys of energy charts not the peaks Less stable also means more reactive Reactions Electron addition 1 2 An electron rich alkene nucleophile attacks an electron poor reagent electrophile forming an intermediate The intermediate electrophile is attacked by an electron rich nucleophile to complete the reactions Mechanisms are how a reaction occurs they show the movement of electrons in the reaction Arrows start at electron source End at an atom empty orbital Markovnikovs rule Tertiary carbocation or equal to allylic carbocation secondary carbocation primary carbocation Carbocation rearrangement A carbocation goes where it is most stable in an alkene reaction o It looks to its neighboring carbons for a more stable place to move to o It can only move once Acid addition Both R and S enantiomers can form if possible
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