Organic Chemistry Lab 318 Spring, 2012

DUE DATES Today –At beginning of lab – Separation Scheme for Nitration of Methyl Benzoate –Spectroscopy Problem Set, Part II, 2. –at end of lab -- copy of laboratory notebook pages for today's experiment (do not turn in your personal notes) Next Week –At beginning of lab - Nitration of Methyl Benzoate Report –Spectroscopy Problem Set, Part II, 3. Two Weeks –Synthesis of 4,4’-di-t-Butylbiphenyl Report –Spectroscopy Problem Set, Part II, 4.

Report from last week Please review the errors you might have made on the Bromination Report. Most likely, you will need to review significant digits; reaction mechanisms (not chemical equations) Notice that the graded parts correspond to the explicit instructions on my web page and the Manual for writing this report. If you have questions about how it was graded, please ask.

Report for next week There are instructions for writing a Synthesis Report in the Manual and on my web site. Please follow the instructions so that you can earn the maximum points. Pay attention to significant digits (0.002 has only one sig. fig.) Note the example for calculation of moles of strong acids such as H 2 SO 4 and HNO 3. Note the example for completing the table on the report form that is the calculation of the theoretical yield. Pay special attention to citing physical property data (M.W., density, etc.) as explained

In Lab Today Synthesis of 4,4’-di-t-butylbiphenyl The reaction is another example of Aromatic Electrophilic Substitution The electrophile is generated from t-BuCl and the FeCl 3 catalyst

In Lab Today The t-butyl carbocation reacts with the  electrons in the aromatic ring to form the arenium ion The electrophile enters the para position because the resulting resonance stabilization also includes the  electrons of the other benzene ring (ortho attack is sterically hindered)

In Lab Today The arenium ion loses a proton (H + ) to regenerate the ring aromaticity The reaction by-product is HCl (gas). The FeCl 3 catalyst is regenerated. A second reaction then takes place on the other aromatic ring to give the final product.

Experiment Notes Set up hot plate in hood; cool 10% HCl – all ready ahead of time Weigh the vial containing biphenyl; empty contents into Erlenmeyer; reweigh vial (±.001 g) FeCl 3 is hydroscopic and must be added quickly Keep reaction in the hood (use the one near you). This is where the Separation Scheme begins (the reaction is over and then 10% HCl is added to begin the separation of the product from the mixture – it removes FeCl 3 ).

Experiment Notes Use a funnel when pouring the acidified reaction mixture into the separatory funnel. Review extraction with separatory funnel and drying agents (p ; ) l Always keep a beaker under the funnel in case of leaks Keep the extract in an Erlenmeyer flask (not a beaker) NEVER throw anything out until you are sure you have your product isolated!

Experiment Notes Review drying agents (p ) –Solution should be in the small Erlenmeyer –Add “some” drying agent with a spatula. Swirl to mix. –Observe the result and consult Table 12.3 p. 697 –Decant into a small beaker; evaporate solvent in Hood See additional instructions for recrystallization from ethanol

In Lab Today Finish the Nitration experiment –Weigh the final product: weigh empty vial, place product in vial, weigh again. –Take melting point of product. Increase temperature slowly Range: from first drop of liquid to complete melting –Properly label the vial containing the product. –Turn the vial in to me before the end of the period. –Cleanup – Chung and Reyes