This experiment is the synthesis of diphenylacetylene from stilbene. Answer the

Question

This experiment is the synthesis of diphenylacetylene from stilbene. Answer the following questions based on the lab report provided.

The bromination part of this experiment could be easily done by adding Br2. What is the purpose of such a reagent like pyridinium perbromide? How do we make .6 M gycol solution? (refer to procedure II).

HBr3 purpose are apfly named "bomb readtors" because of the possibility for acatastrophic explosion Br Br C3 120 160-170°C Please regenerate this table in your metebook filling in any of the blanks Reagent stibrbromide 85% solid potassium hydraxide dibromide Values stilbene Pyridinium formula C14H12 CSHsBr3N C14H12Br2 1.0 expected 1.0 KOH C14Hio equiv 1.0 expected 200 mg 400 mg In general the rate of reaction doubles for every 10 °C rise in temperature moss 200 mg 100 mg 1.11 1.25 mmol 1.11 mmol Quiz ideas 0.588 mmol 1.49 mmol 0.588 mmol melting 124 °C What is a chemical test for the pres- ence of an alkene? 236-237 C 59-61 °C bolling boiding solids 170 *C 19 mm Hg Give a GC quiz for computing % yield. solids solids Calculate the molarity of the starting material in acetic acid. Glassware Set-up Procedure l: To a clean 5 mL conical vial, equipped with a spin vane, is added (E)-stilbene (200 mg) and acetic acid (3 mL). A reflux con denser and a drying tube is attached and the mixture is heated to 120- 130°C until a homogenous solution forms. The drying tube is removed and, while stirring, pyridinium perbromide (400 mg) is added throughIR and C and H NMR the differences Why was sulfolene used in the pre- ceding experiment rather than buta- diene? cidiegenpriment rather than buta- Describe the differences in the MS, between cyclohexenone and cyclo-

Explanation / Answer

1. Standard procedures for the bromination of alkenes create hazards both in the lab and to the environment with caustic agents such as liquid Br2 and chlorinated solvents. Djerassi and Schloz have shown that a sufficient alternative to liquid bromine is the organic salt pyridinium perbromide. This solid is significantly safer to handle, and the molecular bromineis generated in situ (which means “in the reaction mixture”).

2. Molar mass of triethylene glycol = 150.17296 g/mol = 150.17 g/mol

Weight of the glycol = (molarity * molar mass of glycol)*volume in liter

Weight of the glycol = (0.6 M * 150.17 g/mol)*1L = 90.102 grams

Hence 90.102 grams of glycol has to be taken in a 1 liter volumetric flask and make it up to the mark to get 0.6M glycol solution.

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