lecture 14 - 14. Conjugated Compounds and Ultraviolet...

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

View Full Document Right Arrow Icon
14. Conjugated Compounds and Ultraviolet Spectroscopy Based on McMurry’s Organic Chemistry , 7 th edition
Background image of page 1

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

View Full DocumentRight Arrow Icon
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
3 Why this Chapter? Conjugated compounds are common in nature 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) Examine properties of conjugated molecules and reasons for the properties
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 14.1 Stability of Conjugated Dienes: Molecular Orbital Theory 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
5 Measuring Stability Conjugated dienes are more stable than nonconjugated based on heats of hydrogenation Hydrogenating 1,3-butadiene produces 16 kJ/mol less 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
6 Molecular Orbital Description of 1,3-Butadiene The single bond between the conjugated 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
7 14.2 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 note was uploaded on 09/06/2009 for the course CHEM chem 12 AB taught by Professor Adamczeski during the Spring '09 term at San Jose City College.

Page1 / 26

lecture 14 - 14. Conjugated Compounds 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