Fluorocarbons Final (250 pts doubled is 500)
NAME:
1) Easy Questions (70pts)
a) (16pts)
Where does the name fluorine come from?
What is a fluorocarbon?
In general, do these compounds naturally?
What are the three characteristics that make fluorine such a special and unique
substituent?
What does perfluorinated mean?
Name two famous fluorine chemists and state what area of fluorine chemistry they each
contributed to.
Give two similarities between Hydrogen and Fluorine.
Give two differences between Hydrogen and Fluorine.
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b) (22pts)
Draw a Lewis structure with lone pairs for a Fluorine atom; fluorine molecule; fluoride
ion; hydrogen fluoride.
State and briefly explain one historical reason why organofluorine chemistry grew
rapidly during the 1900’s.
Give one possible reason why nature finds it (almost) impossible to synthesize
organofluorine compounds?
Circle which bond is longer
C-H
or
C-F
Circle which bond is stronger
C-H
or
C-F
Circle which bond is more polar
C-H
or
C-F
Circle the molecule with the stronger σ bond:
CBr4
CF4
CF4
CF2H2
BCl3
BBr3
F-F
Cl-Cl
Circle the weakest sigma bond in each molecule:
H
F C H
F
H
HH
F
H
F
H
F
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F
H
H
H
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c) (12pts)
Match the reagents with the correct process:
Pb(OAc)4, HF
Nucleophilic Trifluoromethylation
(CH3OCH2CH2)2NSF3
Electrophilic Trifluoromethylation
CoF3
t
Oxidative Fluorination
CsF, Diglyme
Nucleophilic Epoxidation
BuOOH, tBuLi
Cartman Chiral Fluoridation
F2
Electrophilic Epoxidation
O
F3C
Nucleophilic Fluorination
O
O
CF3
, heat
O
Migratory Insertion
Sharpless Epoxidation
Reductive Defluorination
N
TfO +
F
-
OH
F3C
N
H
Garrison Cycloaddition
/ KOtBu
N
Ph
SF4, HF
F2, H2SO4
KF, Sulpholane
Electrophilic Fluorination
Oxidative Elimination
Radical Fluorination
Radical Trifluoromethylation
DeoxoFluorination
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d) (20pts)
These ten questions are True/False:
Perfluorocarbons and analogous hydrocarbons have similar boiling points.
Hexafluorobenzene will undergo Nucleophilic Aromatic Substitution reactions.
Perfluoroalkyl-alkynes are more stable than fluoro-alkynes.
A Fluorine atom has 10 neutrons.
SF4 is a safer alternative to BAST and DAST reagents.
Perfluorocarbons are normally more dense than hydrocarbons.
Perfluorocarbons will undergo reductive defluorination reactions with strong electron
donors.
Fluoride ion is a worse nucleophile in diethyl ether than in ethanol.
Tetrafluorethene undergoes concerted [2+2] cycloadditions since the WoodwardHoffman rules do not apply to compounds with fluorine substituents.
All compounds containing a C-F bond are very toxic.
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2) Transformations (4x15 = 60pts)
Fill in the products:
C2F5
SelectFluor
F2/N2
HCO2H
CH3CN
CoF3
1) KOH
2)CF3-Si(CH3)3, CsF, THF
O
O
SF4 / HF
OH
3) H2O
Heat
DAST, hexane
PhOK
moist DMF
F3C
CF3
H2O, NaOH
F
O 2N
HF
CH3NH2
CCl3
SbF5
1) Fe, HCl
2) NaNO2, HCl
3) HBF4, heat
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3) Detailed Questions (3x20 = 60pts)
Answer three of the four following questions:
a) Why did the Montreal Protocol seek to put a ban on the production and use of
chlorofluorocarbons?
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b) Explain why even though chloride is traditionally a better leaving group than fluoride,
the following regioselectivity for nucleophilic substitution of chlorotrifluoroethene is
observed.
F
Cl
F
F
CH3OK, CH3OH
F
Cl
H3CO
F
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c) Explain the formation, and the relative ratios, of the three products generated in the
following reaction.
CCl2
CF2
80oC
CCl2
CF2
F2C CCl2
F2C CCl2
(15%)
(83%)
(2%)
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d) Explain why the following halogen exchange (HALEX) reaction works, even though
direct nucleophilic substitution does not occur at highly halogenated sp3 carbons.
F
Cl Cl
Cl
Cl
F
Cl Cl
KF, N.M.P.
180oC
F
F F
F
F
F
F F
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4) Mechanisms (3x20 = 60pts)
Using curly arrows, write mechanisms for three of the four following reactions.
a)
CH3
CH3
HF, SbF5
CCl4
CF3
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b)
F
N S F
CH3CH2
F
CH3CH2
OH
Diglyme
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F
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c)
N
2 equivs. N +
+
F
CH2Cl
2(BF4-)
CH3CN, H2O, reflux
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O
C6H5 C CF2-C6H5
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d)
N
+
N
+
F
CH2Cl
2 (BF4)S
S
F
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