C17: Aromatic Reactions

Question 1

sigma complex what is it

Answer 1

resonance stabilized carbocation, electrophile is joined to the benzene ring by new sigma bond

Question 2

sigma complex is aromatic, anti-aromatic, nonaromatic

Answer 2

not aromatic because sp3

Question 3

electrophilic substitution MECHANISM

Answer 3

[1] double bond attacks electrophile (+) and forms signma complex
[2] base abstracts H, which loses its electron to re-form double bond

Question 4

How do you form an iodine cation?

Answer 4

1/2 I2 + H+ + HNO3 –> I+ +NO2 + H2O

Question 5

Which is a stronger electrophile? what is needed to use the lesser?
I+, Br+

Answer 5

I+, FeBr3

Question 6

cyclohexene + ____ —> 1,2 dibromocyclohexane

trans or cis?

Answer 6

Br2, trans

Question 7

benzene + Br2 —->???

Answer 7

no reaction,

need lewis acid catalyst and will only get bromobenzene

Question 8

benzene + Cl2 in what gives you chlorobenzene?

Answer 8

AlCl3

Question 9

iodination of benzene is different from bromination and chlorination how?

Answer 9

iodination requires an acidic oxidizing agent (Nitric acid) not a catalyst

Question 10

benzene + ____ in ______ —> nitrobenzene

Answer 10

HNO3, H2SO4

or hot Nitric acid (HNO3)

Question 11

aromatic nitro groups (-NO2) are easily reduced to amino (-NH2) by ?????

Answer 11

Zn, Sn, or Fe in aqueous HCl

Question 12

R-benzene + _____ —> R-benzene-NO2 —Zn, Sn, Fe, aq HCl—> ____?

Answer 12

[1] HNO3, H2SO4

[2] R-benzene-NH2

Question 13

benzene + ___ in ____ —> benzenesulfonic acid

Answer 13

SO3 H2SO4

Question 14

what is special about sulfonation?

Answer 14

it is reversible, with the addition of H20, H+ and heat

Question 15

benzene –????—> benzene-d6

Answer 15

large excess of D2SO4/D2O

Question 16

toluene structure

Answer 16

benzene with a methyl group

Question 17

Methyl group of toluene is [1] because it is electron _____ and [2] and therefore

Answer 17

[1] an activating group, donating stabilizing the intermediate
[2] ortho, para-director

Question 18

Toluene + +NO2 is favorable to what substitution? why?

Answer 18

ortho and para because positive charge is spread over two secondary carbons and one tertiary carbon
meta only spreads over three 2ndary carbons

Question 19

energy state highest to lowest of nitration of benzene and toluene

Answer 19

benzene>meta>para,ortho

Question 20

inductive stabilization direction, is it fast or slow

Answer 20

ortho, para-directing, faster tahn benzene

Question 21

alkoxyl groups______ the rate of reaction because they ______
activate what positions?

Answer 21

increase, donate electrons to the pi bond (become + charged), ortho and para

Question 22

anisole (benzene-O-CH3) + 3Br2 in H20 —-> ????

Answer 22

2,4,6-tribromoanisole + 3HBr

benezene-O-CH3 with Br at ortho and para positions

Question 23

aniline (benzene-NH2) –???—> 2,4,6-tribromoanailine + _____

Answer 23

3Br2, H20, NaHCO3

Question 24

activating ortho para directors groups

Answer 24

-O > -N(-R)R > -OH > -OR > -NH-C(=O)R > -R (no lone pairs)

Question 25

activating ortho para directors benzene names

Answer 25

phenoxides > anilines > phenols > phenyl ethers > anilides > alkyl benzenes

Question 26

nitrobenzene –HNO3, H2SO4, 100C–> ????

Answer 26

meta dinitrobenzene

Question 27

electron donating are ____ of reactions

electron withdrawing are _____ of reactions

Answer 27

activators, deactivators

Question 28

energy state highest to lowest of electrophilc addition to benzene and nitrobenzene

Answer 28

ortho,para>meta>benzene

Question 29

deactivating groups are ______, ex:

Answer 29

electron withdrawing,

-NO2, -SO3H, -C(triplebond)N:, -C(=O)R [ketone or aldehyde], C(=O)-OR [ester], -N+R3 [quaternary ammonium]

Question 30

halogenated benzene are _______ and ______directors

Answer 30

deactivating groups, ortho, para-directors

Question 31

chlorobenzene + HNO3 in _____ —> ????

Answer 31

H2SO4, mostly para, ortho, not meta

Question 32

energy state highest to lowest of electrophilc addition to benzene and chlorobenze

Answer 32

meta, ortho, para, benzene

Question 33

activating groups are______ influential than deactivating groups

Answer 33

more

Question 34

substituent strength -OH, -OR, -NR2 ___ -R, -X ____ -C=OR, -SO3H, -NO2

Answer 34

> , >, strongest to weakest

Question 35

benzene + ___ in ___ –> benzene-R

Answer 35

R-X in lewis acid
X = Cl, Br, I
Lewis acid = AlCl3, FeBr3, etc

Question 36

three steps of alkylation

Answer 36

1 form carbocation (R-X + Lewis Acid)
2 electrophilic attack by double bond on carbocation
3 loss of proton on ring by now -lewis acid reforms double bond in ring

Question 37

alkenes + ____ —> carbocation

Answer 37

HF

Question 38

alcohols + ____ —> carbocation

Answer 38

BF3

Question 39

cyclopentanol + BF3 —> ???

Answer 39

cyclopentyl cation

Question 40

Limitations to Friedel-Craft alkylation
1
2
3

Answer 40

1 order matters, activating group then deactivating group or change activating group into deactivating group
2 rearrangement (cannot add n-groups)
3 products are more reactive than starting material (over alkylation)