Friedel-Crafts Alkylations (Exp.II)

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Question of the Day Which organic products can
be formed during the hydrolysis of tert-butyl
chloride? (write the structures of two)
??
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Today- Conclusion of Exp.1 Kinetics- Exp.
2, Friedel-Crafts
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Calculations for Exp.1 Solvolysis
at t10, RCl 0.90 RClo

• Assume you want to determine k in a given
  solvent system at a given temperature, but the
  reaction is too fast to reasonably measure t 10.
  What could you do to obtain k (same solvent/same
  temp.)?
• How could you calculate k by using the half
  life?

0.90RCl
o

kt
-ln
10
RCl
o

kt
-ln
0.90
0.1053
10
0.1053

k
t
10
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Arrhenius Equation and Calculation of Ea and A
R1.987216 cal/Kmol
What does Ea tell us about the reaction?
ln k ln A -Ea/RT
y b m x
Plot ln k vs. 1/T for each solvent mixture
ln k
What is b in our equation, what is m?
1/T
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Friedel-Crafts Alkylations (Exp.II)(Read your
Organic text chapter on Friedel-Crafts
reactions.)
Reaction of p-xylene with 1-bromopropane in the
presence of aluminum trichloride (our lab
experiment) Mechanism?
Aluminum trichloride is a Lewis acid. What is a
Lewis acid? What problems can arise during
Friedel-Crafts alkylations?
Friedel-Crafts reactions increase the number of
C-atoms of the reactant. Do you know any other
reactions that do this, too?
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Friedel-Crafts Alkylations (Exp.II)Lab
Experiment(Microscale procedure. Remember
omission!)
Why does the lab apparatus have to be very dry?
Why is a gas trap needed? What is the meaning
of "tared" (as in "tared flask")? Why is ice
added after the reaction took place? And why ice
and not water?
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Evaluation of products byGas Chromatography
1. What types of samples can be separated by
GC? 2. Which is the moving phase, which is
the stationary phase? 3. What peaks do you
expect in your GC of Exp.II? 4. What determines
their approximate sequence?
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Gas Chromatography / Mass Spectrometry
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Gas Chromatogram of a Crude Oil Sample
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What is the mole ratio? What is the mole
fraction?
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Calculations for Friedel-Crafts Experiment
II. Weight of product mixture What is in
product mixture? Percent by weight of mono
n-propyl product in product mixture Weight
fraction Remember Different molecular
weights Theoretical yield in
grams of mono n-propyl product Balanced
equation (assuming that only mono n-propyl
product is formed), mols, mol ratios Percent
yield mono n-propyl product Actual yield /
theor. Yield x   Ratio of n-propyl to
isopropyl product GC! Area ratio mol ratio
     
3.
1.
4.
2.
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Next time Friedel-Crafts (conclusion) NBS
Bromination (Exp.3) MiniQuiz on Exp1. and 2
(Kinetics and Friedel-Crafts) !