I need to find the limiting reagent, molar equivalent/mole, theoretical yield, and percent yield of aniline and the unknown sample. The starting aniline is 0.5g and the end product is 0.58g. The starting unkown is 0.5g and the end product is 0.56g.

Synthesis of an Analgesic by Acetylation of Aniline
Introduction: Acetanilide is an analgesic that was formally known as Antifebrin1 and is structurally
similar to acetaminophen (or Tylenol). However, unlike acetaminophen, acetanilide is toxic. Acetanilide
is prepared from aniline using an acetylation reaction. Acetylation is often used to place an acetyl
protecting group on primary or secondary amines to reduce their reactivity toward oxidizing agents or
electrophiles.

1.

Cahn, A; Hepp, P. (1886), “Das Antifebrin, ein neues Fiebermittel”, Centralbl. Klin. Med. 1886, 7, 561-65

Objective: In part 1 you will convert aniline to acetanilide using an acetylation reaction described below.
In part 2 you will be given an unknown aromatic amine from table 1 below. The amine will be converted
into its acetamide analog also using the acetylation procedure described below. Your objective is to
compare the two reactions and determine the identity of the unknown amine/acetamide product.

Procedure:
Reagents:
?
?
?
?

Aniline
HCl (concentrated HCl is 37% w/w)
Acetic anhydride
Sodium acetate

Part 1: Dissolve 500 mg of aniline in 14 mL of water. Note that aniline is immiscible in water and two
layers should be observed. Assisted by your GSI add 0.45 mL of concentrated hydrochloric acid and stir.
Measure out 0.6 mL of acetic anhydride and prepare a solution of 530 mg of sodium acetate in 3 mL of
water. Add the acetic anhydride to the solution of aniline hydrochloride in water, mix by swirling, and
immediately add the sodium acetate solution. The solution becomes white as acetanilide precipitates.

Chemistry 216

Cool the solution in an ice bath and collect the solid acetanilide by vacuum filtration. Be sure to weight
the crude solid before purification. Purify by recrystallize from a minimal quantity of ethanol 95%. If
crystals don’t form in a few minutes - it may be necessary to add a small amount of water. Collect the
pure crystallized solid by vacuum filtration. Place the solid in a labeled vial and allow it to dry until the
next lab session. Don’t forget to obtain the mass of your final pure product so that you can calculate %
yield. Characterize the product using TLC, melting point, the Beilstein test and Infrared Spectroscopy.
The product should be co-spotted against a pure sample of starting material. Determine the appropriate
solvent or solvent mixture to use as the eluent.
Part 2: Use the above procedure for acetylation of the substituted unknown aniline. Exact quantities
cannot be calculated since the starting material is an unknown. Be sure to retain your unknown starting
material until you have characterized all reaction products. If you don’t obtain product you may need to
characterize your unknown starting material to determine it’s identity.
Remember that your starting material doesn’t just disappear! If your reaction didn’t work you should be
able to recover something. If it isn’t your product than it should be either unreacted starting material or
an undesired product. In any case you aren’t finished with any 216 experiment until you isolate and
characterize whatever exists in your reaction mixture so that you can figure out what happened. If you
recrystallization doesn’t work – try again or isolate your crude product using an extraction.
The Beilstein test is used to detect the presence halogens in your unknown compound. To perform the
Beilstein test first clean a copper wire by holding it briefly in a flame. Touch the wire to a sample of the
compound (your compound should be dry and free from solvent since halogenated solvents will give a
false positive) and return it to the flame. A blue-gree color in the flame indicates the presence of a
halogen. It is a good idea to test the procedure on a compound known to contain a halogen before
trying it on your own compound.
Reagents:
Compound

CAS Number
62-53-3

Mol. wt.
(g mol-1)
93.13

Concentration
or density
1.022 g/mL

m.p. or
b.p. (°C)
184 (bp)

Aniline

Hydrochloric acid

7647-01-0

36.46

37 wt. % & 1.2
g/mL

>100 (bp)

Acetic anhydride

108-24-7

102.99

1.08 g/mL

Sodium acetate
solution
Acetanilide

127-09-3

82.03

--

138-140
(bp)
--

103-84-4

135.16

--

Chemistry 216

113-115
(mp)

SAFETY NOTES
Corrosive,
acutely toxic,
environmental
hazard
Corrosive,
acutely toxic,
handle with
extreme
caution!
Flammable,
corrosive, toxic
toxic
toxic

Table 1. Unknown Amines with respective boiling and melting points and melting point for the
corresponding acetamide product.

Chemistry 216

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Additional Requirements 
Level of Detail: Show all work 
Other Requirements: I can provide any additional information that you will need but I need all the calculations for both aniline and unknown aniline.