ORGANIC CHEM LAB EXAM 2--
ELECTROPHILIC AROMATIC
SUBSTITUTION (EAS) QUESTIONS
COMPLETE WITH VERIFIED
ANSWERS
\.general overview of EAS experiment - ANSWERS✔-to attempt an EAS reaction
using 4,6,8-trimethylazulene with trifluoroacetic anhydride followed by a water
workup and purification using column chromatography; then conduct NMR
analysis on starting material and product to determine identity of each
\.what were the two starting materials? - ANSWERS✔-4,6,8-trimethylazulene
trifluoroacetic anhydride
\.what was the solvent? - ANSWERS✔-hexanes
\.azulenes are a class of... - ANSWERS✔-aromatic hydrocarbons
\.two reasons azulenes are an interesting class of hydrocarbons - ANSWERS✔-1)
intensely colored (blue or purple usually)
,2) reactivity dominated by molecule's ability to retain aromatic subunits when
undergoing both electrophilic and nucleophilic attack
\.when were azulenes first noticed? - ANSWERS✔-during the isolation of certain
essential oils from plants; some sesquiterpenes (15 C compounds derived from
isoprene units) would undergo isomerization to substituted azulenes during
distillation/other manipulations resulting in distinctive coloration
\.what natural product do azulenes occur in? - ANSWERS✔-crude oil (coloring a
portion of the distillate blue)
\.when were synthetic procedures for azulene prep first developed? - ANSWERS✔-
1950's
\.the reactivity of azulenes illustrates several features of... - ANSWERS✔-non-
benzoid aromaticity
\.what type of electrons does the azulene contain?
what type of system does this qualify the azulene as? - ANSWERS✔-10 pi
electrons
a 4N+2 aromatic system (n=2)
\.azulene is not as aromatic as...
, what is the result of this? - ANSWERS✔-the corresponding benzenoid system
napthalene
azulene is much more reactive toward electrophiles in an EAS type reaction
\.when attacking electrophiles, how does the attack always occur?
what is the result of this? - ANSWERS✔-utilizing the 1 or 3 positions
results in the formation of an aromatic cycloheptatrienyl cation as the sigma
complex intermediate
\.what does nucleophilic attack using the 1 or 3 position result in? - ANSWERS✔-a
larger number of resonance forms than if the 2-position was the nucleophilic
position
\.how does the intermediate return to to a fully aromatic system following
nucleophilic attack using the 1 or 3 position? - ANSWERS✔-by a deprotonation
step
\.which type of rxn typically requires a strong Lewis Acid like AlCl3 or BF3?
what does this type of rxn usually follow? - ANSWERS✔-acylation of benzenoid
aromatics with anhydrides
ELECTROPHILIC AROMATIC
SUBSTITUTION (EAS) QUESTIONS
COMPLETE WITH VERIFIED
ANSWERS
\.general overview of EAS experiment - ANSWERS✔-to attempt an EAS reaction
using 4,6,8-trimethylazulene with trifluoroacetic anhydride followed by a water
workup and purification using column chromatography; then conduct NMR
analysis on starting material and product to determine identity of each
\.what were the two starting materials? - ANSWERS✔-4,6,8-trimethylazulene
trifluoroacetic anhydride
\.what was the solvent? - ANSWERS✔-hexanes
\.azulenes are a class of... - ANSWERS✔-aromatic hydrocarbons
\.two reasons azulenes are an interesting class of hydrocarbons - ANSWERS✔-1)
intensely colored (blue or purple usually)
,2) reactivity dominated by molecule's ability to retain aromatic subunits when
undergoing both electrophilic and nucleophilic attack
\.when were azulenes first noticed? - ANSWERS✔-during the isolation of certain
essential oils from plants; some sesquiterpenes (15 C compounds derived from
isoprene units) would undergo isomerization to substituted azulenes during
distillation/other manipulations resulting in distinctive coloration
\.what natural product do azulenes occur in? - ANSWERS✔-crude oil (coloring a
portion of the distillate blue)
\.when were synthetic procedures for azulene prep first developed? - ANSWERS✔-
1950's
\.the reactivity of azulenes illustrates several features of... - ANSWERS✔-non-
benzoid aromaticity
\.what type of electrons does the azulene contain?
what type of system does this qualify the azulene as? - ANSWERS✔-10 pi
electrons
a 4N+2 aromatic system (n=2)
\.azulene is not as aromatic as...
, what is the result of this? - ANSWERS✔-the corresponding benzenoid system
napthalene
azulene is much more reactive toward electrophiles in an EAS type reaction
\.when attacking electrophiles, how does the attack always occur?
what is the result of this? - ANSWERS✔-utilizing the 1 or 3 positions
results in the formation of an aromatic cycloheptatrienyl cation as the sigma
complex intermediate
\.what does nucleophilic attack using the 1 or 3 position result in? - ANSWERS✔-a
larger number of resonance forms than if the 2-position was the nucleophilic
position
\.how does the intermediate return to to a fully aromatic system following
nucleophilic attack using the 1 or 3 position? - ANSWERS✔-by a deprotonation
step
\.which type of rxn typically requires a strong Lewis Acid like AlCl3 or BF3?
what does this type of rxn usually follow? - ANSWERS✔-acylation of benzenoid
aromatics with anhydrides
