Synthesis of an Aromatic Compound That Smells like Gardenia From Styrene
Heather Myers
Math & Science Department, Cochise College, 901 N. Colombo Avenue, Sierra Vista,
Arizona 85635-2317, United States of America
April 22, 2004
This is a five-step synthesis going from styrene to styrene dibromide, then to
phenylacetylene. Phenylacetylene is converted to acetophenone which in turn becomes
alpha-methylbenzyl alcohol, which then is converted into alpha-methylbenzyl acetate, the
final product.
Through the course of these five reactions, the aromatic ring experiences the
majority of the functional groups taught in the basic course of organic chemistry, making
this a fairly good set of reactions for a lab in a class. They can be seen in the chemical
structures of each molecule below. The low yield on the very first reaction – 12.17% which results in an overall yield of 3.73% alpha-methylbenyl acetate (1) would indicate
that this series is probably not a good reaction for mass production of a perfume agent.
Br
A
Br
B
C
2
1
styrene
O
C
O
CH3
CH3
CH3
E
D
3
CH3
O
OH
4
5
A. Tetrabutylammonium tribromide, dichloromethane, 12.17% yield
B. Tetrabutylammonium hydrogen sulfate, 50% sodium hydroxide, hexane, 86.4%
yield.
C. 88% formic acid, reflux, 58.5% yield.
D. Sodium borohydride, 95% ethanol. Step 2, 6M HCl (aq) 98% yield.
E. Pyridine, dichloromethane, 61.87% yield.
1. Bauer, Kurt/Garbe, Dorothea; Common Fragrance and Flavor Materials. 1985
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Conclusion
This series of reactions was successfully carried out over the course of one
semester in organic chemistry, after the first semester was spent honing the techniques
necessary to complete them. For the first mentioned purpose of this series of reactions,
mission accomplished. As for the gardenia fragrance, it actually caused dizziness and had
a noxious odor, perhaps due to the high concentration in a small laboratory, but the
conclusion must be negative at this time.
Experimental Section
5 mL of dichloromethane and 500 microliters of styrene were placed in a 25mL
Erlenmeyer flask equipped with a stirring bar. TBABr3 was then added (3.16g) over a
period of 1 minute, resulting in a thick yellow gelatinous liquid. The reaction mixture
was then washed with 3mL distilled water, then 3mL 5% sodium thiosulfate twice, then
once more with 3mL distilled water. Solvent was dried with anhydrous sodium sulfate,
then removed by rotary evaporator, 1.41g at an off-white color solid. It was then
redissolved in ethanol and allowed to recrystalize. After recrystalizing, the solid weighed
0.14g, pure white in color, had a melting point of 64 degrees Celcius.
500 microliters of phenylacetylene, then 5mL of 88% formic acid were placed in
a 10mL pear bottom flask equipped with a stirring bar. One hour was allowed for the
reaction to elapse, and thin layer chromatography showed the reaction to be complete.
The reaction mixture was dark brown. The mixture was transferred to centrifuge tube &
washed twice with distilled water. 2mL of dichloromethane was added then allowed to
separate then aqueous phase was removed, washed with dichloromethane, and all organic
phase was combined. Organic phase was then washed twice with sodium carbonate
solution, then twice with distilled water. Solvent was dried with anhydrous sodium
sulfate, then removed by rotary evaporator, 0.32g, light yellow color liquid.
0.60g of styrene dibromine dibromide & 5mL of hexanes were placed in a 25 mL
Erlenmeyer flask equipped with a stirring bar. 2.32g of tetrabutylammonium hydrogen
sulfate (phase transfer catalyst) was then added. 1.45 mL of 12.5M NaOH was added
dropwise and the flask was covered with a watch-glass. The reaction mixture became a
thick yellow gel. Thin layer chromatography showed the reaction to be complete after 45
minutes. The mixture was transferred to centrifuge tube and washed with water, then all
aqueous phase was removed, rinsed with hexane, and all organic material was combined.
Solvent was dried with anhydrous sodium sulfate, then boiled off in a warm sand bath.
Product was a transparent liquid, 0.2g.
500 microliters of acetophenone, then 5mL of 95% ethanol were placed in a
10mL pear bottom flask equipped with a stirring bar. 0.16g of sodium borohydride was
then added, and 30 minutes was allowed to elapse. Thin layer chromatography showed
the reaction to be complete. The reaction mixture was a white liquid. The mixture was
transferred to a beaker and cooled in an ice bath for 10 minutes, then 2mL of 6mL HCl
(aq) was added dropwise, resulting in a clear liquid, H2 gas, and a white precipitate.
Water dissolved the precipitate, then the product was transferred to a centrifuge tube &
the organic layer was extracted with dichloromethane. The mixture was washed with
1. Bauer, Kurt/Garbe, Dorothea; Common Fragrance and Flavor Materials. 1985
2
water and dried by passing it through anhydrous sodium sulfate. Solvent was removed
by rotary evaporator. The product was a light yellow liquid, 0.51g.
500 microliters of alpha-methyl-benzyl alcohol, then 5mL of dichloromethane
were placed in a 10mL pear bottom flask equipped with a stirring bar. 370 microliters of
pyridine were added. 1.42mL acetyl chloride mixed with 1mL dichloromethane was
added dropwise over several minutes. Thin layer chromatography showed the reaction to
be complete after 30 minutes. A thick, white precipitate formed within the reaction
mixture. The mixture was transferred to a beaker and cooled in an ice bath for 10
minutes. Water dissolved the precipitate, then the product was transferred to a centrifuge
tube & the organic layer was washed once with 3M hydrochloric acid, twice with
distilled water, then twice with saturated sodium carbonate, then twice more with water.
The mixture was dried by passing it through anhydrous sodium sulfate. Solvent was
removed by rotary evaporator. The product was a clear liquid, 0.45g.
Styrene: NMR(CDCl3, 4Hz) 3.89 (s, 1 H); 4.09 (s, 1H); 5.10 (m, 1H); 7.31 (s,
5H). IR (KBr)692.85, 1456.11, 770.12, 3855.42, 3448.44, 3841.15, 3752.70 cm-1.
Acetophenone: NMR(CDCl3,) 2.4 (s, 3 H); 7.35(m, 3H); 7.8 (m, 2H);. IR 690.49,
760.04, 1265.62, 1358.99, 1448.43, 1598.43, 1681.73 cm-1. Phenylacetylene: IR
614.47, 628.77, 695.96, 766.60, 887.59, 1213.01, 1488.43. Alpha-methylbenzyl alcohol:
IR 698.59, 759.76, 1010.38, 1076.23, 1451.44, 2970.35, 3350.16. NMR(CDCl3) 1.4 (d,
3H); 1.8 (s, 1H); 4.7 (m, 1H); 7.2 (s, 5H). Alpha-methylbenzyl acetate: IR 699.79,
1029.48, 1065.64, 1209.35, 1241.52, 1371.56, 1745.03. NMR(CDCl3) 1.6 (d, 3H); 2.2
(s, 3H); 46.0 (m, 1H); 7.2 (s, 5H).
1. Bauer, Kurt/Garbe, Dorothea; Common Fragrance and Flavor Materials. 1985
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