CHEM 2211 1nd Edition Lecture 16Outline of Last Lecture I. Alkenes II. Nomenclature for alkenes a. R and S b. E and Z Outline of Current Lecture I. Chapter 5 alkenes Current LectureExamples of how to name and identify E Z and R S. First off lets establish rules for naming: - E and Z naming is used for alkenes - If there is only one double bond then the E or Z goes in front of the whole name - Always goes in parenthesis - R and S naming is used for atoms bonded to 4 different groups - The naming is determined by a priority systemo The higher the atomic number the higher the priority - If 4th priority is attached to a hatched wedge just name the asymmetric center - If it is attached to a solid wedge interchange it with the group on the hatched wedge andname 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.o The configuration after interchanging the groups will be the opposite of the configuration if you just left the groups This means you can leave everything as it is (don’t interchange), name theconfiguration and then use the opposite configuration. Examples: R and S configuration BrC H CH3CH2CH3- Br and CH2CH3 are on the same plane as the center C - H is on a hatched wedge - CH3 is on a solid wedge o Solid wedge is in front of the plane o Hatched is behind the plane Assign priority to the atoms - Br is 1- CH2CH3 is 2- CH3 is 3 - And hatched wedge H is 4 This means we can just assign a configuration no rearrangement needed - We draw an arrow from 1 to 2 to 3 to 4 and see which was it goes - If it is to the right (clockwise) it is R - If it is to the left (counterclockwise) it is S Above I have drawn red arrows to show direction - The configuration is S - The arrows move to the left or counterclockwiseHow would the R configuration of this atom look? BrC CH2CH3 H CH3Assign priority - Br is 1- CH2CH3 is 2- CH3 is 3- H is 4 o H is still on a hatch wedge so No rearrangement needed Draw arrows from 1 to 2, 2 to 3, 3 to 4 - I have done this above with red arrows o R configuration no Clockwise movement E and Z naming examples: E and Z is named on priority of the 4 atoms surrounding the C=C double bond, they are given priority levels high or low on each side. This is based on their atomic number. Higher the number higher the priority Br Cl 1 C=C 2H CH3Give each side high or low priorities 1st C - Br is high priority - H is low priority 2nd C - Cl is high priority - CH3 is low priority Both the high priority atoms are on the top side of the double bond - This means it is Z. - Z means same side o Either top or bottom What does the E atom look like Br CH3C=CH ClAssign priorities 1st C - Br is high - H is low 2nd C- Cl is high - CH3 is low This time the 1st C high priority is above the bond The 2nd C high priority Cl is below the bondThey are on opposite sides of bond there for this is the E
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