Meilen, 16.12.2007

Organic chemistry practical course (OCPI)

HS 07

529-0229-00

Fabienne Vukotic

06-910-541

D-BIOL

Assistant: Guo Xiaoqiang

Synthesis of

Triphenylmethanol

1. Method

The method for the synthesis of Triphenylmethanol is a Grignard reaction with benzophenone and phenylmagnesium bromide as the Grignard reagent.

2. Reaction Equation

3. Mechanism

4. Physical and Chemical Properties of Substances
Calcium chloride dihydrate
CAS: 10035-04-8 / M = 147.02g/mol
ρ = 0.70g/mL / mp = 175 C
/ Risk phrases
- R36: Irritating to the eyes
Safety phrases
- S22: Do not breathe dust
- S24: Avoid contact with skin
Magnesium
CAS: 7439-95-4 / M: 24.31 g/mol / bp: 1090 °C
mp: 648 °C
Mg / CH-toxicity class: free
Risk Phrases
-R11: Highly flammable
-R15: Contact with water liberates extremely flammable gases
Safety Phrases
-S7/8: Keep container tightly closed and dry
-S43: n case of fire, use ... (indicate in the space the precise type of fire-fighting equipment. If water increases the risk add - Never use water)
Iodine
CAS: 7553-56-2 / M: 253.81 g/mol
d: 2.00 g/mL at 25°C / bp: 184 °C
mp: 113 °C
I2 / MAK: 1 mg/m3, 0.1 mL/m3
CH-toxicity class: 2
Risk Phrases
-R20/21: Harmful by inhalation and in contact with skin
-R50: Very Toxic to aquatic organisms
Safety Phrases
-S23: Do not breathe gas/fumes/vapor/spray (appropriate wording to be specified by the manufacturer)
-S25: Avoid contact with eyes
-S61: void release to the environment. Refer to special instructions safety data sheet
Diethyl ether (anhydrous)
CAS: 60-29-7 / M: 74.12 g/mol
d: 0.706 g/mL / bp: 34.6 °C
mp: -116 °C
n20D: 1.3530
/ MAK: 1200 mg/m3, 400 mL/m3
CH-toxicity class: 4
Risk Phrases
-R12: Extremely Flammable
-R19: May form explosive peroxides
-R22: Harmful if swallowed
-R66: Repeated exposure may cause skin dryness or cracking
-R67: Vapors may cause drowsiness and dizziness
Safety Phrases
-S9: Keep container in a well-ventilated place
-S16: Keep away from sources of ignition - No smoking
-S29: Do not empty into drains
-S33: Take precautionary measures against static discharges
Bromobenzene
CAS: 108-86-1 / M: 157.01 g/mol
d: 1.491 g/mL / bp: 156 °C
mp: -31 °C
n20D: 1.559
/ CH-toxicity class: 3
Risk Phrases
-R10: Flammable
-R38: Irritating to the skin
-R51/53: Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment
Safety Phrases
-S61: Avoid release to the environment. Refer to special instructions safety data sheet
Phenylmagnesium bromide
CAS: 100-58-3 / M: 181.31 g/mol
d: 1.01 g/mL at 25°C
/ Risk Phrases
-R12: Extremely flammable
-R14/15: Reacts violently with water, liberating extremely flammable gases.
-R22: Harmful if swallowed
-R34: Causes burns.
-R67: Vapours may cause drowsiness and dizziness.
Safety Phrases
-S16: Keep away from sources of ignition – no smoking
-S33: Take precautionary measures against static discharges.
S36/37/39: Wear suitable protective clothing, gloves and eye/face protection.
-S43B: In case of fire, use fire-fighting equipment on basis of sodium chloride or sodium bicarbonate (never use water
-S45: In case of accident or if you feel unwell, seek medical advice immediately (show label where possible)
-S6A: Keep under nitrogen
S7/8: Keep container tightly closed and dry
Benzophenone
CAS: 119-61-9 / M: 182.22 g/mol
d: 0.70 g/mL / bp: 305 °C
mp: 47-51 °C
/ CH-toxicity class: 4
Risk Phrases
-R36/37/38: Irritating to eyes, respiratory system and skin
-R52/53: Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic environment
Safety Phrases
-S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice
-S61: Avoid release to the environment. Refer to special instructions safety data sheet
Hydrochloric acid (6M
CAS: 7647-01-0 / M = 36.46g/mol
ρ = 1.06g/mL at 25 C / bp =85°C
mp = -25°C
HCl (aq.) / CH toxicity class: 2
MAK: 5ml/m3, 7mg/ml3
Risk-phrases
- R34: Causes burns
- R37: Irritating to the respiratory system
Safety-phrases
- S26: In case of contact with eyes, rinse immediately with plenty of water and seek medical advice
- S36/37/39: Wear suitable protective clothing, gloves and eye/face protection
- S45: In case of accident or if you feel unwell, seek medical advice immediately (show label where possible)
Sodium bicarbonate
CAS: 144-55-8 / M = 84.01g/mol
ρ = 2.16g/mLat 25°C / mp = 270°C
/ CH toxicity class: 5
Safety phrases
S24/25: Avoid contact with skin and eyes
Sodium chloride
CAS: 7647-14-5 / M = 58.44g/mol
ρ = 1.37g/mL / bp =1413°C
mp = 801°C
NaCl / CH toxicity class: non-toxic
Safety phrases
S24/25: Avoid contact with skin and eyes
Sodium sulfate
CAS: 7757-82-6 / M = 142.04g/mol
ρ = 2.68g/mLat 25°C / mp = 884°C
/ CH toxicity class: 5
Triphenylmethanol
CAS: 76-84-6 / M: 260.33 g/mol
d: 0.90 g/mL / bp: 142 °C
mp: 160-163 °C
/ Risk Phrases
-R38: Irritating to the skin
Safety Phrases
-S22: Do not breathe dust
-S24/25: Avoid contact with skin and eyes
5. Experimental Setup
reflux: / vacuum filtration:
6. Amounts of Substance used
Substance / measured amount [ml] / [g] / [mmol] / eq
Magnesium / 0.45 / 18.5 / 2.9
Iodine / 1 crystal / catalyst
Diethyl ether (anhydrous) / 60 / solvent
Bromobenzene / 1.75 / 2.61 / 16.6 / 2.6
Benzophenone / 2.1518 / 6.3 / 1.0
HCl / 3 / 18 / 2.9

Benzophenone is the limiting reactant.

7. Experimental Section (Procedure)

In a 250 mL 3-neck round bottom flask, 0.45 g (2.9 eq.) of magnesium slivers, on I2 crystal, and 20 mL of anhydrous Et2O are stirred together. Actually, it would have been better to take only have as much Et2O. The liquid turns yellow. A solution of 1.75 mL (2.6 eq.) in 20 mL of anhydrous Et2O is added dropwisely. It now starts to reflux ,which means that the reaction has started. The mixture is heated at 35 °C for 15 min and the mixture first becomes milky grey and later it turns to a brownish color; the magnesium is dissolved, now. 2.1515 g (1.0 eq) in 20 mL anhydrous Et2O is added slowly. The solution is now pink but after 1 min it suddenly turns to a soft pink and gets lighter and lighter until it is white. The solution is acified to a pH below 1 with 3 ml of a 6M HCl solution. The color turns to yellow and becomes clear and darker with a second phase which is still milky, light yellow. The two phases are separated in an extraction funnel and the aqeous phase is washed with Et2O (2x 25 mL). The organic phases are collected, washed with saturated NaHCO3 (aq.) (2x 25 mL) and with saturated NaCl (aq.) (1x 25 mL), and dried over MgSO4. The solution is filtered and then concentrated by evaporation of the solvent. The curde product is purified by column chromatography (SiO2, Hexan/EtOAc 20:1 → 5:1, Rf ≈ 0.29, Hexan/EtOAc 10:1) The fractions with the pure product are collected, the solvent is evaporated and the product is characterized.

8. Yield

The theoretical yield is 6.3 mmol. The experimental yield is 1.73 g = 6.65 mmol.

The yield percentage therefore is %

9. Characterization

Melting point

A melting point range of 152.5 -156.1 °C was measured. The literature value for triphenylmethanol is 160 -163 °C.

IR-Spectrum (see attachement)

bands [cm-1] / interpretation
3469 / O-H
3059 / C-H (aromatic)
1596
1489
1444 / C-C

Literature spectrum

http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi

10. Remarks and Discussion

Due to the long procedure the experimental cannot be very high. The measured melting point does not correspond with the literature value, however, by comparing the measured IR spectrum with the literature spectrum the product can be clearly identified as triphenylmethanol.

11. Literature

Coblentz Society, Inc., "Evaluated Infrared Reference Spectra" in NIST

Chemistry WebBook, NIST Standard Reference Database Number 69,

Eds. P.J. Linstrom and W.G. Mallard, June 2005, National Institute of

Standards and Technology, Gaithersburg MD, 20899. NIST Chemistry

Webbook. 4 Dec. 2007 <http://webbook.nist.gov>.

EMolecules - Searching the World's Chemistry. 2007. EMolecules, Inc. 4 Dec.

2007 <http://www.emolecules.com>.

IGS Giftliste. 31 July 2007. BAG. 4 Dec. 2007

<http://igs.naz.ch/igs/igsServer/de.kisters.igs.igs40.servlets.igs40Servlet>.

Kirste, Burkhard. "Chemikalien: Sicherheitsdaten." Institut für Chemie und

Biochemie an der FU Berlin. 28 July 1994. FU Berlin. 4 Dec. 2007

<http://www.chemie.fu-berlin.de/chemistry/safety/chemsafety.html>.

"Risk & Safety." Sigma-Aldrich. 2007. Sigma-Aldrich Co. 4 Dec. 2007

<http://www.sigmaaldrich.com/Help_Pages/Help_Welcome/Product_

Search/Risk___Safety_Statements.html#Safety%20Phrases>.

Sigma-Aldrich. 2007. Sigma-Aldrich Co. 4 Dec. 2007

<http://www.sigmaaldrich.com/Area_of_Interest/Europe_Home/

Switzerland__Schweiz_.html>.