FreeRadicals

1
Chapter 4
2
Free-Radicals
1998 Nobel Prize in Medicine Important Signaling
molecule B.P. regulation and blood
clotting Neutotransmission Immune response
against tumor cells
Oxygen, diradical
3
The free-radical bromination of ethyl benzene has
two propagation steps. The first one is shown

• Draw the second propagation step.
• B.Give 3 possible termination steps.

4
Below are listed several general properties of
reactive intermediates a. sp2 hybridized b.
sp3 hybridized c. divalent carbon d.
trivalent carbon e. nucleophilic f.
electrophilic g. strongly basic h. positively
charged i. negatively charged j..
neutral. k. 3 intermediate is most stable l.
methyl intermediate is most stable m.
stabilized by resonance n. also known as
carbonium ions o. stabilized by neighboring
electron-rich alkyl groups Using the letters
above, classify each type of reactive
intermediate carbocation _______________________
________ carbanion ______________________________
___ free-radical ________________________________
_ carbene (CHOOSE from a-j ONLY)
_____________________
a, d, f, h, k, m, n, o
b, d, e, g, i, l, m
a, d, f, j, k, m, o
a, c, e, f, j
5
List the following radicals in order of
increasing stability (ie, from least stable to
most stable). (CH3)3C, CH2CHCH2, CH3CH2,
CH3, (CH3)2CH
lt
CH2CHCH2
(CH3)3C
CH3CH2
CH3
(CH3)2CH
lt
lt
lt
Me
Pri.
Tert.
Resonance
Sec.
6

• Free-radical chlorination of hexane gives very
  poor yields of 1-chlorohexane, while cyclohexane
  can be converted to chlorocyclohexane in good
  yield.
• How do you account for this difference?