Question

5. A common observation test to confirm the presence of an alkene (or unsaturation, in general) is the bromine test. a. What was the observation in the bromine test that allowed you to conclude an alkene was present? (3 pts.) b. Write the equation for the reaction between the major alkene produced and bromine. Be sure to show the correct stereochemistry in the product. (3 pts.) 6. A sample of 9.0 mL of cyclohexanol was mixed with 2.0 ml of 85% phosphoric acid and heated. The reaction yielded 4.0 mL of cyclohexene. Calculate percent yield for this reaction. (3 pts.) 7. Provide a detailed mechanism for the reaction 2,2-dimethylcyclohexanol with phosphoric acid. Give the major product and do not forget the charges and arrows. (4 pts.)

Answer 1

& Generally Bromine test is done to ensure that if there is an unsaturation y the chemical compound The solution of alkene i generally a coloured solution. When we treat the solution with Br2. leela the colour solution decolo wrises. without an erot evolution of HBr gas. from this observation we can ensure the fact that there was an unsaturation in the chemical compound. The ak alkene solutions got colour due to transition. When we treat the solution with Bro, Icela then the bromination occurs and the a bond does not exist, so , colour disappears. b) The reaction of Brzlecly and alkene goes through by the formation of cyclic bridge Bromonium intermediate Here we use cely as a non polar solvent.

The addition occurs two Br atoms are anti position wirid CH3-CH=CH2 Bolle is the anti addition. attached to the one another. Cheese & BE Br Br In the next step the neucted Phile Bro attacks the 2o carbon atom, which has a greater st character & due to the more electronegative Bra atom than the 10 carlon. CH2H et f anti addition Bror, 11* CH3 Brz BY cala 2 more Bro colourless coloured