organic chemistry b chapter 13 ali phatic cyclic compounds alicyclic compounds by prof. dr
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Organic chemistry B Chapter 13 Ali phatic cyclic compounds Alicyclic compounds By Prof. Dr. Adel M. Awadallah Islamic University of Gaza. Cycloalkanes: Nomenclature. Industrial source. Preparation. Reactions similar to that of alkanes (free radical substitution) , . - PowerPoint PPT PresentationTRANSCRIPT
Organic chemistry BChapter 13
Aliphatic cyclic compoundsAlicyclic compounds
By Prof. Dr.Adel M. Awadallah
Islamic University of Gaza
• Cycloalkanes: Nomenclature
Cyclopropane Cyclobutane Cyclopentane Cyclohexane
OH
OH CH3
Br
OH
OH
Bicyclo[2.2.1]heptane Bicyclo[2.2.2]octaneBicyclo[2.1.1]hexane
Bicyclo[2.2.2]octa-2-ene Tricyclo[2.2.2.02,6]octaneTricyclo[2.2.1.02,6]heptane
Cyclopentanol 1,3-Cyclopentadiene 3-Ethylcyclopentene
2-Cyclohexenol 1-Bromo-3-methylcyclohexane 1,3-Cyclohexanediol
Norbornane
1 2
3
45
6
7
Industrial source
Preparation
Reactionssimilar to that of alkanes (free radical substitution) ,
Reactionsalkenes (addition or cleavage of the double bond)
Ring Strain in Cyclopropane• Average heat of composition per CH2 = 157.4 Kcal / mol• Ring strain in cyclopropane = 27.6 Kcal/mol• Ring strain in cyclobutane = 26.3 Kcal/mol
Ring Strain in Cyclopropane
• Eclipsing (torsional) strain: • Strain resulting from deviation
from the staggered arrangement
• Bond-Angle Strain:• Strain resulting from deviation
from the normal bond angle (tetrahedral 109.5)
Addition to cyclopropane
Addition to cyclopropaneCyclobutane undergoes hydrogenation under vigorous conditions
Relieve of torsional strain in cyclobutanePuckered structure (butterfly)
Relieve of torsional strain in cyclopentaneEnvelope (half chair) structure
• Conformations of Cyclohexane
CH3H
CH3
H
flip
Chair conformation
Boat conformation
axial
equatorial
flip
5% 95%
flip
0% 100%
methylcyclohexane tert-butylcyclohexane
Conformations of cyclohexane
Twist boat is more stable than the boat conformation
1,2 + 1,4 Trans diaxial or diequatorial1,3 cis diaxial or diequatorial
Example