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Halogens replace HydrogensC5H10Cl2 is saturated
ClCl
C6H9Br has 2 degrees of unsaturation
Br
Br
Br
Br
Saturated compounds with Oxygen and Nitrogen
C C
HH
H
H
HH
C2H6
HH
H
C O C
H
HH
C2H6O
N C
H
HHH
C
H
HH
C2H7NCnH2n+2 CnH2n+2O CnH2n+3N
Determine the # elements of Unsaturation
C8H10Br2OC8H18 is saturatedcompound is deficient by 6 "H's"3 degrees of unsaturation
O
BrBrCH2OH
CH3
Br
Br
e.g.
OH Br
Br
Alkyl Groups with -Bonds
CH=CH2
Br
cis 1-bromo-3-vinylcyclohexane
a vinyl group CH2CH=CH2
4-allylcyclopentene
an allyl group(or ethenyl)(or 2-propenyl)
a phenyl group
3-phenyl-1-nonene
3,3-dimethyl-1,4-cyclohexadiene 2-butyl-1,5-hexadiene
(E) 1-ethylidene-2-methylcyclopentane3-allylcyclohexene
Hyperconjugation bond associates with adjacent C-H bond
CC
C
mono-substituted disubstituted
C
1-butene trans 2-butene
Markovnikov’s Rule
The addition of H-X across a double bond results in the more
highly substituted alkyl halide as the major product.
Addition of HBr or HClMarkovnikov Addition
Markovnikov
Br
C CH
H
HCH3
CH3
HBr
CH3
CH3
CH
HC
CH3
CH3C
H
H
Br
C
H
not formed
Definitions• Regioisomers – two constitutional isomers
that could result from an addition reaction. • Regiospecific – only one regiosisomer
forms at the expense of the other.• Regioselective – both regioisomers are
formed, but one is formed in preference.
Hammond’s Postulate
• Related species that are close in energy are close in structure.
• In an endothermic reaction, the transition state is similar to the product in structure and stability.
• In an exothermic reaction, the transition state is similar to the reactant in structure and stability.
• i.e. the structure of the transition state resembles the structure of the most stable species.