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Halogenation of a Substituted Benzene Ring
By: John Doe
CHEM 210(1 or 2, as appropriate)L – Lab Day (M, T, W, R, or F)
Date(s) Lab Performed (don’t forget any days you collected additional data.)
Sample Report (Be sure to Double Space your formal report)
Abstract
The purpose of this experiment was to halogenate a substituted benzene ring. Acetanilide, a
substituted benzene ring, was reacted with bromine in acetic acid and hydrobromic acid at
room temperature to prepare para-bromoacetanilide. A product was obtained in a yield of 0.12
g (86%) and with a melting point of 150-157 °C. An infrared spectrum of the product showed
bands at 3300, 1700, 1600 and 1500 wavenumbers (or use cm-1). A 1H NMR of the product
showed signals at 2.04, 7.45, 7.56, and 10.02 ppm. The halogenation of a substituted benzene
ring (acetanilide) with bromine was successful since parabromoacetanilide was obtained as
shown by melting point, infrared, and 1H NMR analysis.
Introduction
Get background from McMurry (and/or other referenced material) regarding the reaction that
was carried out. For example, who discovered it, significant intermediates, and/or why it is
important.1(show references after each new statement of fact)
Reaction (all rxns and mechanisms must be drawn by you and NOT shared)(sharing=cheating)
Give the overall chemical reaction with structures and names of all reactants and products.
Make sure you include the reaction conditions (solvent/temp/etc.) above and below the reaction
arrow. (Draw this using ChemDraw software) (Best to use this format once you open
ChemDraw: File-> Apply document settings from->ACS document 1996)
Mechanism
Be sure to draw the reaction mechanism (just as shown in class to be safe). Give the
mechanism specific to this reaction using structures and arrows. You must use the software
ChemDraw (or other chemical drawing software, but be sure it is neat and has good resolution.)
Experimental details2(where you found the experimental details)
Acetanilide (0.090 g, 0.67 mmol), glacial acetic acid (0.5 mL), and a spin vane were placed in
a 5 mL conical vial. The vial was fitted with an air condenser and placed in a 23 – 27 ºC water
bath. The mixture was stirred to dissolve the acetanilide. A mixture of 2.5 M bromine/7.7 M
hydrobromic acid (1.0 mL, 2.5 mmol Br2) was added to the vial through the top of the air
condenser while the reaction mixture was stirred continuously. A drying tube was packed
loosely with cotton moistened with 1 M sodium bisulfite solution (0.5 mL) and attached to the
air condenser. The reaction mixture was stirred for an additional 20 minutes. The product was
isolated as follows. The reaction mixture was transferred to a 10 mL Erlenmeyer flask
containing water (5 mL) and saturated sodium bisulfite solution (0.5 mL). The mixture was
stirred and additional saturated sodium bisulfite solution (0.5 mL) was added until the red color
signifying the presence of bromine disappeared. The vial was placed in an ice bath for 10
minutes. The solid product was collected by vacuum filtration on a Hirsch funnel. The product
was allowed to dry for one week. The yield and melting point of the product were measured.
Infrared and 1H NMR spectra of the product were obtained.
Results
Yield: 0.12 g, 0.56 mmol, 86%. Melting point: 150-157 ºC. IR: (thin film/NaCl) 3300 cm-1 (NH), 1700 cm-1 (C=O). 1H NMR (60 MHz, CDCl3 w/TMS) δ 2.04 (CH3, s, 3H), 7.45 (Ar-H, d,
J=8.34 Hz, 2H), 7.56 (Ar-H, d, J=8.34 Hz, 2H), 10.06 (N-H, broad s, 1H) ppm.
Theoretical yield: 0.090 g acetanilide (1 mol/135 g) (1 mol para-bromoacetanilide/ 1 mol
acetanilide) (214 g/mol) = 0.14 g para-bromoacetanilide. Percent yield: (0.12 g/0.14 g) 100% =
86%
Sample Report (Be sure to Double Space your formal report)
Discussion
The product yield was 0.12 g (86%). (Give some good reasons why your percent yield was
less than 100%. Think about the limitations inherent in the procedure as well as your own
limitations. Also, think about what you observed during the entire procedure that gives
evidence that product was lost.)
If there is evidence of significant impurity, based on any of your data, this evidence
must be discussed. For example, you must always discuss the melting point data: The melting
point of the product, 150 – 157 ºC, had a range of 7 ºC and was depressed 11 ºC from that of
the literature value for p-bromoacetanilide, 168 ºC3(where did you get the literature value?) indicating that
the product is impure.
The product was identified as p-bromoacetanilide based on the melting point, infrared
and 1H NMR data.
Conclusion
The purpose of this experiment, the halogenation of a substituted benzene ring, acetanilide,
with bromine was met since p-bromoacetanilide was obtained, as shown by melting point,
infrared and 1H NMR analysis. (or was it not confirmed by your results? Then say so)
References
1. McMurry, J. Organic Chemistry, 6th ed.; Brooks/Cole Publishing Co.; Pacific Grove,
2004, p number. (or pp numbers.)
2. Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G. Introduction to Organic
Laboratory Techniques: A Microscale Approach, 3rd ed.; Saunders College
Publishing; New York, 1999, pp 338 – 342.
3. www.chemfinder.com/para-bromoacetanilide (accessed March 15th, 2009)
Attach 8.5 x 11” copies of appropriate spectra
This is a FORMAL lab report and all efforts to strictly follow the below guidelines is important.
Note: (check these off to be sure you followed the rules)
Write out the full name of an element when talking about it “hydrogen” not H in the report
Use Times New Roman or Arial Font, Size 12
Double-space
Words or letters like “cis” “trans” “anti” “syn” “R” “S” “E” “Z” must be italicized
Be sure to use proper symbols (example - ˚C not degrees C or just C)
Be sure to use proper subscript and superscript when appropriate
Place one space between a number and its units (except percent)(this includes M and ˚C)
Lab reports are always written in 3rd person (no I’s and Me’s)
Experimental is past tense (you are telling us what you did)
Use a zero to hold the decimal place for numbers less than one
Liter is abbreviated with a capital L (even in mL)
Attach 8.5 x 11” copies of spectra, when appropriate
Show all work on spectra, when appropriate
Staple your report in the upper left corner
Don’t start sentences with a number
No references should be placed in the abstract
Example for references – Dr. Brent Feske was the first to report this synthesis in 1999.1 (place the
superscript number after the period)(references should be in numerical order as they occur in the
written document)