Organic Chemistry Lab 315
Fall, 2014
DUE DATES
• Today
– At beginning of lab – GC of Distillate
Report
– At end of lab -- copy of laboratory
notebook pages for today's experiment
• Next Week
– Synthesis of tert-Pentyl Cl Report
– See my lab web site for instructions on writing
Synthesis reports.
Report Notes – Last Week
• Instructions said to show on the graphs the
data used to estimate the volumes of Et and
Bu acetate.
• In the summary, the assumptions would
include explaining how you decided which data
to use.
• The summary should include the fact that you
actually graphed vol. vs. T data.
• Instructions said to explicitly compare the
mole % calculated for each method.
– That does not mean “about the same”, or “less
than 10% difference”, etc.
Notes
• The next slides show the mechanism for the
formation of a tertiary alkyl chloride from a
tertiary alcohol. The specific example used is
tert-butyl. You can easily re-write it using tertpentyl.
• When you look up the reaction starting
materials, products and by-products you will
likely need to use the systematic IUPAC names.
• tert-Pentyl is also known as tert-amyl.
In Lab Today
•Synthesis of tert-butyl chloride
– The mechanism of the reaction is SN1
CH3
CH3 C OH
CH3
CH3
H Cl
CH3 C O
CH3
H
Cl
H
Step 1 is an acid/base reaction
between HCl (acid) and alcohol
(base) to form the oxonium ion.
Step 2 is the dissociation of the
oxonium ion to form the tert-butyl
carbocation and the leaving
group, H2O.
Step 3 is the reaction (Lewis
acid/base) between the
carbocation and the nucleophile,
Cl-, resulting in overall
substitution.
In Lab Today
•Synthesis of tert-butyl chloride
– The mechanism of the reaction is SN1
CH3
CH3
CH3 C OH
H Cl
CH3 C O
CH3
CH3
CH3
CH3 C
CH3
H
CH3
OH2
CH3 C
CH3
H2O
Cl
H
Step 1 is an acid/base reaction
between HCl (acid) and alcohol
(base) to form the oxonium ion.
Step 2 is the dissociation of the
oxonium ion to form the tert-butyl
carbocation and the leaving
group, H2O.
Step 3 is the reaction (Lewis
acid/base) between the
carbocation and the nucleophile,
Cl-, resulting in overall
substitution.
In Lab Today
•Synthesis of tert-butyl chloride
– The mechanism of the reaction is SN1
CH3
CH3
CH3 C OH
H Cl
CH3 C O
CH3
CH3
CH3
CH3 C
OH2
CH3 C
H2O
CH3
Step 2 is the dissociation of the
oxonium ion to form the tert-butyl
carbocation and the leaving
group, H2O.
CH3
CH3
CH3
Cl
H
CH3
CH3
CH3 C
H
Step 1 is a Bronsted-Lowry
acid/base reaction between HCl
(acid) and alcohol (base) to form
the oxonium ion.
Cl
CH3 C Cl
CH3
Step 3 is the reaction (Lewis
acid/base) between the
carbocation and the nucleophile,
Cl¯, resulting in overall
substitution.
In Lab Today
• Reaction takes place within a
separatory funnel
• tert-pentyl alcohol and HCl are
mixed to form one phase initially,
and then begin to react.
• As the products tert-pentyl
chloride and water form, the
reaction mixture separates into
two phases.
In Lab Today
• Two phases are the upper tPentCl phase (with some water
and aq. acid) and the lower
aqueous phase with dissolved
acid.
• Separate the phases (keeping
upper phase in funnel).
• Wash the t-PentCl layer with
water (removes ___?)
• Add aq. sodium bicarbonate. The
basic bicarbonate neutralizes the
acid and forms CO2 gas.
In Lab Today
• Wash the t-PentCl with water
again (removes __?)
• The t-PentCl will be mostly pure
with just a small amount of water
present.
• Review drying organic solvents
(See p. 696 in Pavia)
• Decant t-PentCl into clean dry
pre-weighed vial (± .001g).
• Do not distill.
Experiment Notes
• Determine the refractive index, take an IR
spectrum and calculate the percentage
yield.
• Store t-PentCl product in a tightly capped
vial in the storage drawer.
• Dispose of aqueous solutions in the sink
with plenty of water.
Synthesis Report
•See the instructions on the web site for
writing a Synthesis report.
•Pay particular attention to the table on the
Report Form, which is actually a calculation
of theoretical yield.
•A strong acid, HCl is used as a reagent, so
be sure to follow the instructions for
calculating the amount
•Separation scheme -- flow chart of
procedure for separating a pure product
from reaction by-products. (Even though
you do not do a final distillation, include it
on the Separation Scheme.)
Lab Clean-up
• Muhammad Siddiqui