Chapter14 - 14 Conjugated Dienes and Ultraviolet...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
14. Conjugated Dienes and Ultraviolet Spectroscopy Based on McMurry’s Organic Chemistry , 6 th edition ©2003 Ronald Kluger Department of Chemistry University of Toronto
Background image of page 1

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

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 2 Conjugated and Nonconjugated Dienes Compounds can have more than one double or triple bond If they are separated by only one single bond they are conjugated and their orbitals interact The conjugated diene 1,3-butadiene has properties that are very different from those of the nonconjugated diene , 1,5-pentadiene
Background image of page 2
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 3 Polyenes Compounds with many alternating single and double bonds Extended conjugation leads to absorption of visible light, producing color Conjugated hydrocarbon with many double bonds are polyenes (lycopene is responsible for red color in tomatoes) Extended conjugation in ketones (enones) found in hormones such as progesterone
Background image of page 3

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

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 4 14.1 Preparation and Stability of Conjugated Dienes Typically by elimination in allylic halide Specific industrial processes for large scale production of commodities by catalytic dehydrogenation and dehydration
Background image of page 4
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 5 Measuring Stability Conjugated dienes are more stable than nonconjugated based on heats of hydrogenation Hydrogenating 1,3-butadiene takes up 16 kJ/mol more heat than 1,4-pentadiene
Background image of page 5

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

View Full DocumentRight Arrow Icon
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 6 14.2 Molecular Orbital Description of 1,3-Butadiene The single bond between the conujgated double bonds is shorter and stronger than sp 3 The bonding π -orbitals are made from 4 p orbitals that provide greater delocalization and lower energy than in isolated C=C The 4 molecular orbitals include fewer total nodes than in the isolated case (See Figures 14-1 and 14-2) In addition, the single bond between the two double bonds is strengthened by overlap of p orbitals In summary, we say electrons in 1,3-butadiene are delocalized over the π bond system Delocalization leads to stabilization
Background image of page 6
McMurry Organic Chemistry 6th edition Chapter 14 (c) 20 7 14.3 Electrophilic Additions to Conjugated Dienes: Allylic Carbocations Review: addition of electrophile to C=C Markovnikov regiochemistry via more stable carbocation
Background image of page 7

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

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 01/03/2012.

Page1 / 26

Chapter14 - 14 Conjugated Dienes and Ultraviolet...

This preview shows document pages 1 - 8. Sign up to view the full document.

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