alkenesIg

alkenesIg - Copyright, Arizona State University...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Alkenes I 1 Copyright, Arizona State University Copyright, Arizona State University Alkenes I Electrophilic Addition (more. ..) • sometimes called olefins (by me!) 1 Alkene Structures chemistry of double bond C C σ C–C BDE ~ 83 kcal/mol π + σ C=C BDE ~ 146 kcal/mol therefore : π -bond ~ 146 - 83 = 63 kcal/mol • pi-bond is weaker than the sigma-bond • thus, electrons in the pi-bond are higher in energy than those in the sigma-bond How do you break a pi bond? D D H H C C rotate D D H H C C rotate D H H D C C cis-isomer trans-isomer zero overlap of p orbitals: π bond broken! 90° D D H H D H D H Energy 90° 180° ~ 63 kcal/mol Distinguishing isomers trans- cis- what about? Br cis- or trans-? Br Need a different system : Z/E notation, Cahn-Ingold-Prelog convention "rules" 1). Assign priorities to groups attached to each alkene carbon according to atomic # 2) Compare 2nd, 3rd etc. atom away from carbon as necessary, look for first point of difference 3) Multiple bonds "add up" 4) If 2 highest priority groups on same side, then Z, otherwise E Z = zusammen - together (z ame side!) E = entgegen - opposite Examples: Br priority priority 2 1 2 1 highest on same side therefore: Z-alkene!
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Alkenes I 2 Copyright, Arizona State University Cl H 1 2 1 2 highest on same side therefore: Z-alkene! H 2 1 1 2 highest priority on opposite sides therefore: E-alkene! 2 Alkene Nomenclature Rules 1) Look for longest chain containing the double bond ( AND any other functional groups, e.g. halides) 2) Assign lowest numbers to carbons based on the alkene and number through the C=C bond 3) Use the "ene" suffix Examples CH 3 CH CH CH 2 CH 3 1 2 3 4 5 2-pentene cyclohexene (the 1 can be assumed) Br Cl bromine gets 4 alphabeticaly 4-bromo-5-chlorocyclohexene 1 2 3 4 5 • the alkene always gets the 1, always count "through" the double bond 1 2 3 4 5 6 7 3-propyl-1-heptene Br 1 2 3 4 5 6 7 8 build name "in pieces" (3,E)-octene 3-methyl 7-bromo-5-ethyl-3-methyl-(3E)-octene (2E, 4E)-hexadiene
Background image of page 2
Alkenes I 3 Copyright, Arizona State University Copyright, Arizona State University Alkenes I PROBLEMS Alkene Nomenclature In each case, give the IUPAC name for the provided structure 1 (easier) Cl Answer Correct Y / N 2 (easier) (CH 3 CH 2 ) 2 C=C(CH 3 ) 2 Answer Correct Y / N 3 (easier) Answer Correct Y / N 4 (standard) Answer Correct Y / N 5 (standard) Br Answer Correct Y / N 6 (standard) Cl Answer Correct Y / N 7 (standard) Br I F Cl Answer Correct Y / N 8 (standard) Answer Correct Y / N 9 (standard) Cl Answer Correct Y / N 10 (standard) Answer Correct Y / N Answers provided on the website. ... Doing problems is the only way that you will learn organic chemistry. You should do problems in the notes, from the textbook and from problem sets. It is CRITICAL that you keep track of what you know and what you don't know. Each notes problem has a "Correct Y / N" box. When you are PROPERLY CONVINCED that you can do a problem, circle "Y", if you can't do the problem circle "N". Keep coming back to those problems with the circled "N", until you can circle the "Y".
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/07/2012 for the course CHM 233 taught by Professor Skibo during the Fall '08 term at ASU.

Page1 / 23

alkenesIg - Copyright, Arizona State University...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online