CHML211
Exp. 8 Bromination of Stilbene—Green Synthesis
IN-LAB ASSIGNMENT: (EACH STUDENT will record the following data in his/her laboratory notebook in a well organized
manner during lab period. Yellow carbon copies will be submitted for grading along with Post-Lab assignment.) …..max
score = 20 pts.
6. Data/Calculations
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
Initial mass of trans-stilbene used
Initial volumes of 48% HBr and 30% H2O2 used
Mass of small filter paper
Mass of empty watch glass
Mass of watch glass+ filter+ product
Mass of final product
Physical state and color of product
Theoretical yield calculations based on all 3 reactants!
% yield calculation
TLC diagram
All Rf calculations
7. In-lab Questions (The following question should be answered in laboratory notebook.)
a.
Draw the complete mechanism for the synthesis of the product formed from the addition of Br 2 to 1,2dimethylcyclohexene using curved arrows to indicate the movement of electrons.
CH3
CH3
+
Br
Br
?
MW: 110.2 g/mol
b.
Based on the previous question, calculate the theoretical yield based on 1.0 g of the 1,2-dimethylcyclohexene.
The molecular weight of the starting alkene is given, but the molecular weight of the product must be
determined using the product structure. Be sure to include units.
CHML211
Exp. 8 Bromination of Stilbene—Green Synthesis
POST-LAB ASSIGNMENT: (EACH LAB GROUP will submit one copy of a typewritten, paragraph style report addressing
all of the points listed below. Must be written using PAST TENSE, PASSIVE VOICE. ) …..max score = 50 pts.
8. Experimental




(Write 1-2 paragraphs including all of the following. Do NOT present a bulleted outline.)
What type of reaction was performed?
Describe the actual synthetic procedure. Include names of any reactants used and desired product, as well as
name of solvent and catalyst used (if any). Be sure to give actual volumes/masses of compounds used during the
synthesis (not just what the lab manual tells you to use).
Describe the purification technique used to isolate the desired product. Be sure to give names and actual
volume/mass of any compounds used during the purification process.
Describe the analytical technique (TLC) used to evaluate the product, including preparation of TLC sample, names
and actual volume of TLC solvent used during analysis, visualization method used to detect compounds, and how
compounds were identified using this technique.
9. Results (Complete, then copy/paste completed tables into your document.)
Table 8.1 Experimental results
Final Mass of product (g)
Theoretical Yield (g)
Percent Yield
Product Appearance
Compound
Table 8.2 TLC results
TLC Rf values
Standard
Sample
Stilbene
Dibromostilbene
10. Discussion (Write 1-2 pages addressing all of the following points.)




Describe in detail the two conditions that used in this experiment that made it “greener” than typical bromination
procedures.
Restate the name of the reactants combined and the name of the product formed during the synthesis. State the
final product mass and the calculated percent yield for the synthesis. Be sure to report these values using the
correct units.
Based on the TLC results, were the reactants completely converted to the desired product? Explain this
conclusion by stating the calculated Rf values of each standard provided, along with the calculated Rf value(s) of
any compound which appears in the sample lane. Be sure to report Rf values using correct significant figures.
Include a short comment addressing what could be done differently to improve the experimental results if
repeated.