benzene

styrene

(C6H5)CH=CH2

friedel crafts

(benzene ring with R group) make R group add to benzene ring with AlCl3 catalyst

Substituents affects two aspects of Electrophilic aromatic substitution:

1) The rate of the reaction: can react faster of slower than benzene. 2)The orientation: New group located either ortho, para, or meta to the existing substituent. The identity of the first substituent determines the position of the second substituent.

3 facts about Friedel Crafts Alkylation

1) Vinyl halides and aryl halides do not react in Friedel-Crafts alkylation. (the carbocations that could be for from these species are too unstable. 2) Rearrangements can occur in order to form a more stable carbocation electrophile. 3) Other functional groups that form carbocations can also be used as starting materials. Ex. Alkenes, alcohols are common and used in the presence of a strong acid.

ortho

1,2 positions

meta

1,3 positions

para

1,4 positions

Electrophilic aromatic substitution reactions

1. Halogenation (Br/FeBr3, Cl/FeCl3, or I/HNO3) 2. Nitration (NO3/ H2SO4) 3. Sulfonation (H2SO4) 4. Friedel-Craft acylation (Acyl chlorides with AlCl3) 5. Friedel-Craft alkylation(alkyl chlorides and AlCl3, possible rearrangement)

Aromatic Compounds

1. a compound must have an uninterrupted cyclic cloud of x electrons above and below the plane of the molecule. And they are unusually stable 2. the x cloud must contain an odd number of pairs and x electrons.

TNT

2,4,6-trinitrotoluene, the 3 nitro groups give explosive properties

-NO2, -SO2, -CN

3 possible deactivating groups

triol

3OH

-OH2, -NH2, -OR, -NR2, alkyl

5 possible activating groups

monosubstituted

A benzene with one additional group is....

disubstituted

A benzene with two additional groups is...

aromatic compound

A cyclic hydrocarbon with delocalised pi electrons

hydroxyl group

A functional group consisting of a hydrogen atom joined to an oxygen atom by a polar covalent bond. Molecules possessing this group are soluble in water and are called alcohols.

3

A meta substituent of a benzene is in position ___ relative to the primary substituent

4

A para substituent of a benzene is in position ___ relative to the primary substituent

ortho

A substituent of a disubstituted benzene that is next to the primary substituent

para

A substituent of a disubstituted benzene that is three down from the primary substituent

meta

A substituent of a disubstituted benzene that is two down from the primary substituent

deactivating group, meta director

A substituent of an aromatic compound that slows down electrophilic substitution

activating group, O-P director

A substituent of an aromatic compound that speeds up electrophilic substitution

benzyl

A toluene as a substituent without a hydrogen on its methyl group is called a ____ group

RCOCL/AlCl₃

Acylation Benzene ring is treated with an acid chloride. The transfer of an acyl group from one atom to another.

RCl/AlCl₃

Alkylation The transfer of an alkyl group from one atom to another (from Cl to Benzene)

Br+

An example of a powerful electrophile

2

An ortho substituent of a benzene is in position ___ relative to the primary substituent

Relative stability

Aromatic compound > cyclic compound with localized electrons> anti-aromatic compound

phenyl, aryl

As a substituent, an aromatic ring is called either a ___ or a ___ group

phenol

Benzene ring with an OH group directly attached to it

xylene

Benzene with two methyl groups in ortho, para, or meta positions

ether

C-O-C, a compound containing an oxygen bonded to 2 carbon atoms

phenyl group

C6H5-, Benzene ring attached to a parent compound

benzene

C6H6, leukemia

arene

Compound derived from benzene

All activators are?

Either R groups or have an O or N atom bonded to a lone pair bonded directly to the benzene ring.

Anti-aromatic Compounds

Even number of x electron pairs

X₂/FeX₂ X=Cl₂ or Br₂

Halogenation

electrophile

In electrophilic aromatic substitution, this replaces a hydrogen in the original molecule

M

In the presence of a deactivating group, the electrophile is most likely to be added at this position

O, P

In the presence of an activating group, the electrophile is most likely to be added at this position

positive charge stabilised by resonance

Intermediate step in an electrophilic substitution reaction

HNO₃/H₂SO₄

Nitration

anisole

OCH3 attached to a benzene ring

KMnO₄

Oxidation

Substituent causes electron donating in benzene

Polarizable alkyl groups donate electron density, and thus exhibit an electron-donating inductive effect.

Nitrobenzene

Reacts more slowly than benzene in all substitution reactions. Electron withdrawing NO₂ group deactivates the benzene ring to electrophilic attack. NO₂ is a meta director.

H₂, Pt/2000 psi

Reduction of Ring and Substituent to Single Bonds

H₂/Pd

Reduction of Substituent to Single Bonds

Zn(Hg), HCl or NH₂ NH₂ + OH-

Reduction to Alkyl

Pd/H₂ or Fe/HCL or Sn/ HCL

Reduction to Aniline

Ortho, Para directors and activators

Substituents that activate (make more reactive) a benzene ring and direct substitution ortho and para. Ex. -R or -Z:

Ortho, Para Deactivators

Substituents that deactivate (less reactive) a benzene ring and direct substitution ortho and para. Ex. All halogens.

nitration

Substitution of a nitro group (-NO2) for one of the ring H. The reaction occurs when benzene reacts with nitric acid in the presence of sulfuric acid as catalyst

SO₃/H₂SO₄

Sulfonation

Electron withdrawing groups destabilizes?

The Carbocation and deactivate a benzene ring towards electrophilic attack.

Electron donating groups stabilize?

The carbocation and activate a benzene ring towards electrophilic attack.

stable

The delocalised pi electrons in an aromatic compound mean it is very...

effect of a Halogen directly bonded to a benzene ring

The inductive effect dominates and the net effect is electron withdrawal.

electrophilic aromatic substitution

The most important reaction of aromatic rings

powerful

The property the electrophile must have to participate in electrophilic aromatic substitution

Neutral O or N atom bonded directly to benzene

The resonance effect dominates and the net effect is electron donation.

benzene

The simplest aromatic compound

cyclic, delocalised pi electrons

The two defining features of an aromatic compound

Resonance effect "electron donating"

When resonance structures place a negative charge on carbons of the benzene ring. * observed whenever an atom Z having a lone pair of electrons is directly bonded to a benzene ring.

Resonance effect "electron withdrawing"

When resonance structures place a positive charge on carbons of the benzene ring. *observed in substituted benzenes having the general structure C₆H₅-Y=Z where z is more electronegative than Y.

phenyl substituent

a benzene ring is a substituent, it is called a phenyl group

toluene

a benzene ring w/ a methyl group ** reacts faster than benzene in all substitution reactions.

benzyl substituent

a benzene ring with a methylene group is called a benzyl group. -CH2-

simmons smith

a carbenoid reacts with a alkene to form a cyclopropane

mercaptans

a common name for any molecule containing an -SH group

All meta directors have

a full partial positive charge on the atom bonded to the benzene ring.

aryl group

a group derived from an arene by removal of an H atom from an arene and given the symbol Ar-

steric effects

a group influences another group by filling space

polynuclear aromatic hydrocarbon

a hydrocarbon containing two or more benzene rings, each of which shares two carbon atoms with another benzene ring

pyridine

a ring with a non carbon atom

zwitter ion

an ion with both + and - charges in same ion

deuterium

an isotope of hydrogen which has one neutron (as opposed to zero neutrons in hydrogen)

diol

any of a class of alcohols having 2 hydroxyl groups in each molecule

All ortho and paradirectors

are R groups or have a non bonded electron pair on the atom bonded to the benzene ring.

Kahn Ingold Prelog rules

are a set of rules used in organic chemistry to name the stereoisomers of a molecule. assign an R or S descriptor to each stereocenter and an E or Z descriptor to each double bond

benzoic acid

benzene with a -O= -OH group

benzonitrile

benzene with a 3 (-) N

Toluene

benzene with a CH3 group Ch3 group is an ortho, para director.

Anisole

benzene with a CH3O group

styrene

benzene with a CH=CH2 group

Aniline

benzene with a NH2 group

benzenesulfonic acid

benzene with a SO3H group

benzaldehyde

benzene with a aldehyde mark

Phenol

benzene with an OH group

Resonance effects of substituent on benzene ring

can either donate or withdraw electron density, depending on whether they place a positive or negative charge on the benzene ring.

geminal carbon

carbon attached to same parent carbon

electrophilic aromatic substitution

chemistry of benzene rings

aromatic sextet

closed loop of electrons (two from the second bond of each double bond) characteristic of a benzene ring

wurtz reaction

coupling of C atoms to make alkane (couple free radicals)

All deactivators are?

either halogens or they have an atom with a partial or full positive charge bonded directly to the benzene ring. These are electron withdrawing groups.

hoffman product

formed by reaction with a big bulky base. Potassium T Butoxide

initiator

free radical that starts polymerization

alcohols

functional group, OH bonded to tetrahedral carbon atom

exocyclic

hoffman product

Substituent causes electron withdrawing in benzene

more electronegative atoms than carbon pull electron density away from carbon and thus exhibit an electron-withdrawing inductive effect.

thiols

organic compounds containing sulfhydryls (-SH) group bonded to a tetrahedral carbon

Lindlar reaction

reduces triple bonds to double bonds using a heterogenous catalyst. This stops a reaction

carbene

sp2 hybridized carbon atom, has a lone pair

Meta directors

substituents that direct substitution meta. all meta directors deactivate the ring. Ex. -Y(delta + or minus) order in increasing deactivation: -CHO, -COR,-COOR, -COOH, -CN, -SO₂H, -NO₂, N⁺R₃

dehydration

the elimination of a molecule of water from an alcohol. OH is removed from one carbon and H is removed from the other

hydrogen bonding

the intermolecular force in which a hydrogen atom that is bonded to a highly electronegative atom is attracted to an unshared pair of electrons of an electronegative atom in a nearby molecule

endocyclic

zaietz's rule