Ochem Lab: Bromination of Arenes

purpose of experiment

studying rates of free-radical bromination rxns with various substrates

predict what order the compounds will react and then compare that to the observed order

general rxn for bromination of arene

R-H + Br2 --> R-Br + HBr

experiment probes...

the rate at which C-H bonds in diff molecular environments undergo radical bromination

C-H bonds

generally unreactive but do act as functional grps in rxns that emply radical halides

compounds tested

toluene, ethylbenze, t-butylbenzne, methylcyclohexane and cyclohexanee

short story of procedure

rate reactivity experiment involving 5 test tubes under the light

things to be aware of for ethyl benzene and toluene

both react very quickly and may change color before have a chance to finish with the other samples

best to save these 2 for last so you can focus on determining which reacts faster

rinse test tubes with ___ before disposing in glass waste containers

DCM

What experimental criterion is to be used to measure the rates of bromination of the hydrocarbons used in this experiment?

color change

What is the type of mechanism in regards to the bromination reaction that is taking place in this experiment?

Free-radical substitution

Which of the following statements regarding this reaction is true?

The hydrocarbon is used in excess.

rectifying bromine spill

pour some sodium thiosulfate around the spill; red color will slowly disappear at which the mess can be treated as halogenated organic waste or wiped up with paper towels and discarded in the trash

do NOT waste...

cyclohexene

smells terrible and the less you use the better; only need a single drop for each test tube/rxn that is still red

never wash glassware that contained bromine with...

acetone

What solvent should not be used to clean any glassware that has come into contact with Br2?

acetone