Researcher

Matthew McBride

Objective

To determine the extinction coefficient of trans-dibenzalacetone in ethanol

Procedure

Dissolve a known amount of trans-dibenzalacetone in ethanol and calculate the extinction coefficient using UV/Vis Spectroscopy and Beer's law.

Results

UV/Vis spectrum for Solution A_10000dilution
A Mode:
Spectrum of Solution A_10000dilution
[USE: spectrumtype=UV-Vis in URL, e.g.
http://lxsrv7.oru.edu/~alang/ChemDoodleWeb/spectrumwidget.php?spectrumtype=UV-Vis&url=http://onschallenge.wikispaces.com/file/view/ONSEXP332A_10000dilution_Amode.jdx/356679886/ONSEXP332A_10000dilution_Amode.jdx -AL]
Spectrum of Ethanol
Spectrum of difference (Solution A_10000dilution - ethanol)
λ max: 321 nm
Absorption units at λ max (A): 0.240677 (cannot look at spectrum to obtain this number, but must look at .jdx file directly)
Pathlength (L): 1 cm
Concentration (c): 2.1298e-6 M
Calculated extinction coefficient (ε) of trans-dibenzalacetone in ethanol using Beer's Law (A=εLc): 113004

E1 Mode:
Spectrum of Solution A_10000dilution
Spectrum of Ethanol
Spectrum of difference (Solution A_10000dilution - ethanol)
λ max:
Absorption units at λ max (A):
Pathlength (L): 1 cm
Concentration (c):
Calculated extinction coefficient (ε) of trans-dibenzalacetone in ethanol using Beer's Law (A=εLc):

Discussion

The spectrometer provided a spectrum that "jumped" around a lot and it is believed that the insufficient washes were being completed to obtain a reliable value.

Conclusion

The extinction coefficient (ε) of trans-dibenzalacetone in ethanol was calculated to be 113004, but this extremely high.

Log

2012-08-06

15:36 Added 0.0499 g of trans-dibenzalacetone (Product 284A from UCEXP284) into a 10 mL volumetric flask.
15:40 Filled the flask with ethanol. All of the crystals dissolved into the solution. The flask was inverted several times to mix. This was Solution A (0.021298 M).
15:44 Added 50 µL (0.0361 g) of Solution A into a 5 mL volumetric flask and filled with ethanol. The solution was inverted several times to mix. This was Solution A_100dilution.
15:50 Added 50 µL (0.0344 g) of Solution A_100dilution into a 5 mL volumetric flask and filled with ethanol. The solution was inverted several times to mix. This was Solution A_10000dilution.
17:00 3 mL of Solution A_10000dilution was added to a cuvette and analyzed by UV/Vis spectroscopy. The sample was analyzed in both E1 and A mode. The sample and the blank (ethanol) were analyzed using the same cuvette.