1) What is the number of moles of formic acid and water in 4.5 mL 95% formic acid? Assume percent is by weight and the density is 1.25 g/mL.
2) What is the difference between paraformaldehyde and formaldehyde? Please explain it in detail.
3) What are the dangers involved in using formic acid and paraformaldehyde?
4) Show the complete mechanism for the formation of the product of the reaction. You must include the protonation step of the electrophile. Also, please calculate the theoretical yield of the reaction, and include the name of the product if known.
a. Two molecules of 1,3,5-trimethylbenzene undergo a Friedel-Crafts alkylation with formaldehyde catalyzed by formic acid.
5) The intermediate benzylic carbocation is stabilized by resonance. Draw the contributing resonance structures.
6) What is the purpose of washing with Na2CO3 in the work-up procedure?
To 0.75 g of paraformaldehyde in a 50-ml round-bottomed flask in the hood, add 4.5 mL of 95% formic acid. Fit the flask with a reflux condenser and bring the mixture to a boil on an electrically heated sand bath. After about 5 min, most of the paraformaldehyde will have dissolved. Add through the condenser 10.0 mL of mesitylene. Reflux the reaction mixture for 2 h., cool the mixture to room temperature, and then cool it in ice. Remove the product by vacuum filtration in the hood, taking great care not to come into contact with the residual formic acid. Wash the crystal with water, aqueous sodium carbonate solution, and then again with water and squeeze the crystal beween sheets of filter paper to dry. Determine the weight of the crude product and save a few crystals for MP determination. Recrystallize the product.
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