The Synthesis of Diphenyl Succinate

Date January 2004

Objective: In this experiment, diphenyl succinate (DPS) will be synthesized from succinic acid (SA) and phenol. The product will be isolated from the reaction mixture by extraction and tested as growth stimulant for selected fungi species.

Reaction:

Table of quantities: Aldrich Chemicals, 2000-2001; *HC&P, 52^nd Ed.

Substance	mmoles	Grams	mL	m.p. (°C)	b.p. (°C)	M.W. (g/mol)	d (g/mL)	Amnt. used
Succinic acid	1.0	0.118	21.0	182		118.09	-	0.120 g
phenol	2.0	0.188	5.0	40-42	182	94.11	1.071	0.191 g
Phosphorus oxychloride	1.1	-	0.103	1.25	105.8	153.33	1.645	104 mL
Diphenyl succinate				121 *	222.5^15*	270.29 *

Calculations:

1. Theoretical yield:

Limiting reagent: succinic acid

2. Percent yield Mass of empty 50-mL Erlenmeyer flask: 30.120g

Mass of product + flask: 30.301 g

Mass of product (actual yield): 0.181 g diphenyl succinate

Percent yield = (actual yield/theoretical yield) X 100% = (0.181 g/ 0.272 g) x 100% = 66.5%

Procedure:

In a 3-mL vial, combine succinic acid, phenol and POCl₃ and heat mixture at 115^oC for 1.25 h under hood. Allow to cool and add 0.5 mL of toluene and heat the mixture again at 115^oC for 1.25 h under hood. Allow mixture to cool and decant top layer. Extract HPO₃ residue with toluene and combine extracts in a small vial. Remove toluene by slow heat and N₂ purge. Cool mixture in ice-bath to precipitate diphenyl succinate. Wash solid product with diethyl ether and dry product under vacuum for 30 min.

Observations:

Reaction mixture began to bump after 35 min. of heating. Heating appeared to be uneven and after adjustment of heat source heating became smooth again. After 55 minutes of heating, the reaction mixture had gradually turned yellow. After an additional 15 minutes of heating, the reaction mixture began to darken further and the reaction was stopped at this point (5 min shorter than required in procedure). Heating the mixture in toluene went without any complications. Noticeable amount of acidic gas evolved during heating; gas was tested using litmus paper under hood, most probably HCl gas (indication that reaction proceeds as expected). Combined toluene extracts were light yellow color. Colorless diphenyl succinate crystals precipitated out of cooled toluene solution. Crystals remained colorless after diethyl ether wash.

Characterization:

1. Physical properties

The product was isolated as clear, colorless crystals with no odor. The majority of crystals were the shape of needles.

2. Spectroscopy

The infrared spectrum of the product (attached) displayed a strong peak at 1758cm^-1, consistent with the formation of an aryl ester. Furthermore, C-H stretching peaks were observed both above and below 3000 cm^-1, also consistent with the presence of both H-C(sp³) and H-C(sp²) bonds. No traces of an O-H stretch were visible in the spectrum, indicating an efficient conversion of both acid and alcohol groups.

The ¹H NMR spectrum of the product (attached) consisted of two sets of peaks: d 2.31 (s, 2H), the protons next to carbonyl carbon; d 7.10 (m, 5H), the protons of the aromatic ring. The only additional peak present is a small sharp peak centered at d 5.4 which is probably due to the residual phenol present in the final product.

Conclusions:

The synthesis of diphenyl succinate proceeded smoothly and efficiently with only a minor adjustment in the original procedure. The purity of the product is satisfactory although a residual amount of impurity was detectable by ¹H NMR. The separation by decanting is effective but perhaps not the best way to isolate the product due to possible inclusion of phenol as shown the by ¹H NMR. No other significant impurities were present in the isolated product.