Chemistry 331 - Fall 1996

Chapter 4 - Alkenes & Alkynes

Practice Exercises

Nomenclature


Reactions

complete a reaction given any two components:


Regiochemistry / Stereochemistry

recognize those reactions that are regioselective (Markovnikov Rule)

recognize those reactions that are stereoselective (syn / anti)


Conjugated Dienes

compare the pi molecular orbitals of the following:

1,2-pentadiene / 1,3-pentadiene / 1,4-pentadiene / 1,3,5-cyclohexatriene

write a complete mechanism for the acid-catalyzed addition of water to 1,3-pentadiene, showing both 1,2 and 1,4 addition products

(Hint - first add H+ as an electrophile, then add water as a nucleophile)


Resonance

draw all of the resonance forms for the following:

indicate whether the forms are equivalent - if not, predict the best resonance form

also describe what the resonance hybrid would be expected to look like

all of the above cations could have come from the addition of H+ to some polyene

identify a possible starting polyene for each case and indicate if there are multiple possibilities