question

methyl benzoate is reacted with ____ to form ___?

answer

-reacted with a mixture of nitric acid and sulfuric acid -methyl m-nitrobenzoate is the major product

question

Electrophilic Aromatic Substitution: a reaction in which....?

answer

-a reaction in which the hydrogen atom of an aromatic ring is replaced as a result of an electrophilic attack on the aromatic ring -hydrogen on aromatic ring REPLACED by electrophilic agent (meta* or ortho/para)

question

Methyl Benzoate: has partial positive charge on the carbonyl carbon and is electron-______

answer

withdrawing

question

Methyl Benzoate is activating or deactivating?

answer

deactivating

question

Methyl Benzoate is ____-directing

answer

meta?director

question

In Electrophilic Aromatic Substitution reactions, a _______ is needed to react with the aromatic ring; In this experiment _____ was used.

answer

-strong electrophile -nitronium ion

question

The nitronium ion will be generated in situ* by mixing ___&____

answer

mixing nitric acid and sulfuric acid

question

in situ* means?

answer

it forms in the reaction mixture

question

n a mixture of the nitric acid and sulfuric acid, ____ will act as the "base" and will be ____

answer

nitric acid; protonated

question

The protonated intermediate ________ leading to nitronium ion formation

answer

loses water

question

Attacks on the ortho and para positions result in _____

answer

destabilized cationic intermediates (minor products)

question

attack at the meta position yields ______

answer

a less destabilized intermediate (MAJOR PRODUCT)

question

how do you "add the pre?cooled concentrated nitric acid/sulfuric acid mixture to the methyl benzoate/sulfuric acid mixture?"

answer

drop-wise (pipet)

question

How is the product isolated?

answer

--> Collect the product using a Büchner funnel --> Wash the solids with cold water and methanol (very soluble) --> Recrystallize

question

product formed in this reaction?

answer

methyl m-nitrobenzoate

question

are aromatic compounds reactive or unreactive to nucleophiles? Why?

answer

-VERY unreactive -surrounded by pi-electron clouds (nucleophiles attack carbonyl carbon) -electrophiles better sutied

question

why are highly reactive electrophilic reagents needed for reacting with aromatic compounds?

answer

-results in loss of resonance stabilization

question

____ acts as a base in this reaction

answer

nitric acid

question

activating group

answer

-Any substituent on a benzene ring that causes the rate of electrophilic aromatic substitution to be greater than that for benzene -Usually groups that have a lone pair on the atom connecting to the ring directly are activating and thus makes the ring reactive -able to donate a lone pair into the ring to attack another "substrate" for a reaction - allows subsequent substituents to add onto the ring more readily

question

deactivating group

answer

-An electron-withdrawing group (NO2) attached to the benzene ring that decreases the reactivity of the ring towards electrophilic substitution reaction. =Most deactivating groups are meta directors (but halogens are deactivating ortho-para directors) =Any substituent on a benzene ring that causes the rate of electrophilic aromatic substitution to be lower than that for benzene =if the atom attached to the ring is attached to an electronegative atom also= deactivating --> electrons are getting pulled away from the ring, thus unreactive

question

what is the deactivating group on methyl benzoate?

answer

methyl ester group (COOCH3)

question

methyl ester group on methyl benzoate is ___-directing?

answer

meta directing (electron-withdrawing group)

question

what is/are the minor product(s) of this experiment?

answer

ORTHO/PARA PRODUCTS: --> methyl o-nitrobenzoate --> methyl p-nitrobenzoate

question

why is the temperature kept at or below 15 degrees?

answer

-to avoid excessive formation of byproduct -At higher temperatures there is a greater chance of getting more than one nitro group substituted onto the ring (dinitro) -To minimize some side reactions, which occur at a slower rate, while allowing the desired reaction to proceed

question

After the nitration reaction of Methyl Benzoate, why is product poured onto ice instead of water? exothermic/endothermic?

answer

-The reaction between H2SO4/hno3 is exothermic, so splashing is less likely if the heat from disassociation is used to heat the ice -Using ice will prevent the temperature from getting too high

question

NMR: ____ is used as solvent

answer

CDCl3

question

NMR: ____ is used as standard

answer

TMS (tertramethylsilane)

question

how was methyl benzoate "weighed?"

answer

volume necessary using density (D=M/V)

question

HNO3 + H2SO4 (yields?)

answer

[NO2+ (nitronium ion) ] + [HSO4-] + [H2O]

question

The higher the temperature, the _____

answer

the greater the amounts of dinitration products formed from this reaction

question

the reaction takes place at the meta position because the ortho and para positions are _______?

answer

-destabilized by adjacent positives charges on the resonance structure -NO2 is a deactivating group causing itself to be a meta director

question

What would you expect the structure of the dinitro products to be?

answer

1,3-dinitrobenzene; Nitro groups "direct" new groups into the 3 position (and possibly 5 position) -1,3,5-trinitro possible??? --->nitro groups make the ring much less reactive than the original benzene ring. Two nitro groups on the ring make its reactions so slow that virtually no trinitrobenzene is produced under these conditions

question

NO2+ nitronium ion that is generated from ____

answer

HNO3

question

If the bottom of the flask is not cool to the touch while adding HNO3:H2SO4 solution, what should you do?

answer

slow down the rate of addition of the mixture--> exothermic

question

why do we wash with methanol?

answer

because the ortho and para products are more soluble in methanol and impurities can be removed

question

Is HNO3 or H2SO4 the catalyst?

answer

-H2SO4 is the catalyst (not used up) -HNO3 is NOT a catalyst (nitronium ion, NO2+, is formed from this acid)

question

[-CO-OCH3] -> ___activating ___ director

answer

deactivating m director

question

[-Br] -> ___activating ___ director

answer

deactivating o/p director

question

[-CO-CH3] -> ___activating ___ director

answer

deactivating m director

question

[-CH3] -> ___activating ___ director

answer

activating o/p director

question

[-OCH3] -> ___activating ___ director

answer

activating o/p director

question

[-CN]--> ___activating ___ director

answer

deactivating m director

question

ortho product=

answer

(2,6)

question

para product=

answer

(4)

question

meta product=

answer

(3,5)

question

[-X]: ___activating ___ director

answer

deactivating o/p director

question

[-OR]: ___activating ___ director

answer

activating o/p director

question

[-OH]: ___activating ___ director

answer

activating o/p director

question

[-NH2/NHR/NR2]: ___activating ___ director

answer

activating o/p director

question

[-CH3]: ___activating ___ director

answer

activating o/p director

question

[-CN]: ___activating ___ director

answer

deactivating m director

question

[-NO2]: ___activating ___ director

answer

deactivating m director

question

[-COOH]: ___activating ___ director

answer

deactivating m director

question

[-COOR]: ___activating ___ director

answer

deactivating m director

question

[-CHO]: ___activating ___ director

answer

deactivating m director

question

[-COR]: ___activating ___ director

answer

deactivating m director

question

[-SO3H]: ___activating ___ director

answer

deactivating m director

question

Why is H2SO4 added to the reaction mixture?

answer

-To serve as the solvent -To protonate nitric acid, promoting nitronium ion formation -Because it is a stronger acid than HNO3 (weaker base)

Exp. 3b: Nitration of Methyl Benzoate – Flashcards

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