Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
Synthesis of
tert-butyl chloride
Natalja Früh, 07-922-404, D-CHAB, [email protected]
Assistant: Alexey Federov
1
Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
1. Theory
1.1.
Reaction
1.2.
Mechanism
RDS
The mechanism for the synthesis of tert-butyl chloride is a nucleophilic substitution of type SN1 of
tert-butanol with hydrochloric acid (HCl).
A nucleophilic substitution of type SN2 doesn’t occur, because the center is sterically hindered.
A side reaction that could occur would be an elimination of type E1 with product isobutene. This side
reaction is preferred by high temperature.
The second step is the rate-determining step (RDS), in which a carbocation is formed, when the C
goes from sp3-hybridization to sp2-hybridization.
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Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
2. Procedure
2.1.
Experimental setup
2.1.1. Extraction
separation funnel
organic phase
aqueous phase
100
100 mL
75
50
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Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
2.1.2. Distillation
contact thermometer
30o
vigreux column
100 m L
in
out
cooling water
250 m L
LaboBib
300
50
©
AN
AN
AUS
AUS
1500
100
0 U/min
250
500
o
C
200
150
1000
750
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Organic chemistry practical course
Autumn semester 2008
2.2.
Synthesis of tert-butyl chloride
26.10.2008
Procedure
20.68g of tert-butanol and 65ml of HCl (37%) are put into a 500ml seperatory funnel and mixed
together. After vigorous shaking for about 5 minutes, there are two phases, an organic one and an
aqueous one. The aqueous phase is due to the higher density on the bottom and can be discharged.
The organic layer (upper) is washed three times with 20ml saturated NaHCO3 to neutralize the
remaining HCl and once with 25ml saturated NaCl to fetch the remaining H2O out. Each time the
funnel is shaken for short time, the device is opened while the funnel is upside down to let the
accumulated gas escape.
The organic phase is put into a 100ml round-neck-flask and a spattle of CaCl2 is added to dry. The
substance is purified by distillation under atmospheric pressure, as the boiling point of the product is
around 51°C. The measured vapor temperature is between 47°C to 50°C as expected.
Important for the distillation is, that the first and the last few drops are collected in a small flask
because these drops could be impure and contaminate the product.
After the distillation the product is kept in a round-neck-flask closed by a stopper due to the low
boiling point.
2.3.
Results
2.3.1. Yield
Substance
Amount
[mol]
Equivalent/yield
tert-butanol
HCl (37% / ~ 12M)
tert-butyl chloride
discarded drops (distillation)
20.68 g
65 ml
15.46 g
0.75 g
0.279 mol
0.8 mol
0.167 mol
~ 0.01 mol
1 eq
3 eq
60% (yield)
~ 3 % (yield)
2.3.2. Refractive index
A refractive index of n20D = 1.383 is measured, the literature value of tert-butyl chloride is
n20D =1.3856.
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Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
2.3.3. Infrared spectrum
Literature
Measured spectrum
Bands [cm-1]
2990 - 2950
1470
1456
1370
1150
809
Interpretation
C-H stretching vibration
C-H deforming vibration
C-C vibration
C-Cl stretching vibration
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Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
7
Organic chemistry practical course
Autumn semester 2008
Synthesis of tert-butyl chloride
26.10.2008
3. Physical and Chemical Properties of Substances
tert-butanol
C4H10O
CAS: 75-65-0
Molecular Weight
Density
Refractive Index
Risk phrases
 R11
 R20
Safety phrases
 S9
 S16
74.122 g/mol
d254 0.78 g/cm3
n20D 1.3823
Melting Point
Boiling Point
25.5° C
82.8 ° C
Highly flammable
Harmful by inhalation
Keep container in a well-ventilated place
Keep away from sources of ignition – no smoking
CH Toxicity class 4
MAK 100ml/m3; 300mg/m3
hydrogen chloride (37%)
HCl
CAS: 7647-01-0/37
Molecular Weight
Density
Risk phrases
 R34
 R37
Safety phrases
 S26
HCl

S36/37/38

S45
36.461 g/mol
d25 1.19 g/ml
Melting Point
Boiling Point
-25° C
85° C
Causes burns
Irritating to the respiratory system
In case of contact with eyes, rinse immediately
with plenty of water and seek medical advice
Wear suitable protective clothing, gloves and
eye/face protection
In case of accident or if you feel unwell, seek
medical advice immediately (show label where
possible)
CH Toxicity class 2
MAK 5ml/m3; 7mg/ml3
Sodium hydrogen
carbonate
NaHCO3
CAS: 144-5-8
Molecular Weight
Density
Refractive Index
84.007 g/mol
d25 2.159 g/cm3
n20D 1.500
Melting Point
decomposes around 50° C
Safety phrases
 S24/25
Avoid contact with skin and eyes
CH Toxicity class 5
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Organic chemistry practical course
Autumn semester 2008
Sodium chloride
NaCl
CAS: 7647-14-5
Synthesis of tert-butyl chloride
26.10.2008
Molecular Weight
Density
58.442 g/mol
d25 2.16 g/cm3
Melting Point
Boiling Point
Safety phrases
 S24/25
Avoid contact with skin and eyes
801° C
1413° C
NaCl
CH Toxicity class non-toxic
Calcium chloride
CaCl2
CAS: 10043-52-4
CaCl2
tert-butyl chloride
C4H9Cl
CAS: 507-20-0
Molecular Weight
Density
Risk phrases
 R36
Safety phrases
 S15
 S25
Molecular Weight
Density
Refractive Index
Risk phrases
 R11
Safety phrases
 S7/99



S16
S29
S33
110.983 g/mol
d25 2.15 g/cm3
Melting Point
Boiling Point
772° C
>1600° C
Irritating to eyes
Keep away from heat
Avoid contact with eyes
92.568 g/mol
d15 0.85 g/cm3
n20D 1.3856
Melting Point
Boiling Point
-25° C
52° C
Highly flammable
Keep container tightly closed and in a wellventilated place
Keep away from sources of ignition – no smoking
Do not empty in drains
Take precautionary measures against static
discharges
CH Toxicity class 4
4. Sources
Combined Chemical Dictionary, Taylor & Francis Group, 2008
http://ccd.chemnetbase.com/dictionary-search.do?method=view&id=2145609&si=
Verein Biologie Studierender, 2008
http://www.vebis.ch
AIST, National Institute of Advanced Industrial Science and Technology (Japan), 2008
http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi
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