Org. Synth. 1957, 37, 2
DOI: 10.15227/orgsyn.037.0002
BENZOYLACETANILIDE
[Acetanilide, 2-benzoyl-]
Submitted by C. F. H. Allen and W. J. Humphlett
1.
Checked by Max Tishler and R. Connell.
1. Procedure
A mixture of
105.7 g. (0.55 mole) of ethyl benzoylacetate and
46.6 g. (0.5 mole) of aniline (Note 1) is placed in the
dropping funnel D (
Fig.4) at the top of the
continuous reactor (Note 2) and
(Note 3) after the column has been heated to 135° (transformer set at 80 volts)
(Note 4) and
(Note 5). The reactants are then admitted to the column during about 15 minutes (this corresponds to a rate of amide formation of 396–400 g. per hour). Alcohol distils
(Note 5) noticeably from the column during the addition and collects in flask
G. At the completion of the reaction,
100 ml. of xylene is passed through the hot column to rinse out the residual amide
(Note 6). An additional
200 ml. of xylene is added to the
receiver C, and solution is effected by warming. After the solution has been cooled enough to induce crystallization,
100 ml. of petroleum ether (b.p.
35–60°) is added with manual stirring. The mixture is chilled to 15°, then the crystalline product is separated by suction filtration and washed
300–400 ml. of petroleum ether. The yield is
99–100 g. (
83–84%), m.p.
106–106.5° (Note 7). The melting point of this product is not altered by recrystallization from
benzene (Note 8),
(Note 9),
(Note 10).
Fig. 4.
2. Notes
1.
Commercial grades of ethyl benzoylacetate and aniline were freshly redistilled before use.
2.
The continuous reactor shown in
Fig. 4 is of general utility for reactions that proceed at a rapid rate. Optimum conditions must be determined by experiment for each new product, but a high yield may often be secured. To determine a yield, it is necessary to run a given weight of the components through, rinse the column, and work up the combined products.
3.
The reactor is built from stock pieces of glassware having 29/42 and 24/40 standard taper joints. It consists of a
column 100 cm. long, of 2 cm. inside diameter, in two 50-cm. sections. The column is packed with 1/8-in. glass helices such as are used for packing distillation columns. The column is heated by two 275-watt flexible heating tapes
A, 6 ft. long and ½ in. wide, with lead wires connected to variable transformers, which are attached to a source of 110-volt power. The heating elements may be covered with asbestos tape if desired. At the bottom of the column is a
500-ml. flask C for receiving the product. At the top of the column is a
250-ml. addition funnel D (a cylindrical shape is convenient for calibration of volume or for winding with heating tape in instances where melting a solid or heating a solution is required). The addition funnel is connected to the column through a section
B having a side arm provided with a
thermometer E and a
downward condenser F leading to a 500-ml. flask
G, which has an outlet to the atmosphere for effluent gas.
4.
It is always desirable to use a "wet" column; once a column has been used, this condition prevails. It is advantageous to admit a little
xylene while regulating the heater, before addition of the reactants.
5.
With two 275-watt heating tapes, the required temperature inside the column is secured at a voltage setting of about 80. If alcohol does not distil noticeably during the reaction, the internal temperature is not high enough and the
transformer should be adjusted, or more time should be allowed for preheating the column.
6.
Part of the product solidifies in the receiver.
7.
This compares with 74–76% yield by the batch process.
28.
Recrystallization from
benzene produces a whiter product in
92% recovery.
9.
This procedure may be used to prepare other substituted anilides. If one of the components is a solid, it can be dissolved in an excess of the other. For instance,
46 g. of 2-amino-5-nitroanisole in
285 ml. of hot ethyl benzoylacetate is passed through in 30 minutes, with a transformer setting of 70 volts; then the column is rinsed with 50 ml. of the ester. The product crystallizes in the receiver and is separated by filtration; the filtrate is used to make up more of the reacting component mixture. The work-up yields
75–76 g. (
89%) of amide with the correct melting point (
178.5–180°) and color. When the same amide is made by a batch procedure, the yield is only
81% of a product melting at
130–150°. This illustrates the advantage of short time of exposure to heat in the continuous reactor.
10.
This reactor has also been used with other types of reactions.
|
|
|
Voltage
|
Time, hr.
|
Mole Ester
|
Yield, %
|
|
|
Ethyl benzalmalonate (batch) (cont.)3
|
|
18
|
0.63
|
90.8
|
|
|
65
|
0.5
|
0.69
|
82
|
|
3-Carboxy-4-hydroxyquinoline4
|
90
|
0.66
|
|
35
|
|
4-Benzal-2-phenyl-5-oxazolone (batch) (an azlactone) (cont.)5
|
|
|
|
64
|
|
|
60
|
0.25
|
>
|
73
|
|
3. Discussion
This preparation and
oleoyl chloride (p.739) illustrate the use of the general form of a laboratory-sized continuous reactor.
6 This device has many advantages over the commonly used flasks (batch procedure). In particular, the short time of exposure to heat results in a better quality of product, as shown by less color, fewer side reactions, and better melting point, often unchanged by recrystallization. Furthermore, the unlimited capacity, very short reaction time, and use of concentrated solutions permit a larger output with no increase in size of apparatus and less delay required for removal of solvents.
The continuous reactor is most useful with reactions that take place at a relatively rapid rate. Its wide versatility enables it to be used in many types of reactions.
Benzoylacetanilide was selected as an example because it has previously appeared in
Organic Syntheses.2This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
petroleum ether
Benzene (71-43-2)
aniline (62-53-3)
xylene (106-42-3)
Ethyl benzalmalonate
Ethyl benzoylacetate (94-02-0)
Benzoylacetanilide,
Acetanilide, 2-benzoyl- (85-99-4)
2-amino-5-nitroanisole (97-52-9)
3-Carboxy-4-hydroxyquinoline
4-Benzal-2-phenyl-5-oxazolone (842-74-0)
Oleoyl chloride (112-77-6)
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