Transcript HL Option G Organic Chemistry

HL OPTION G ORGANIC
CHEMISTRY
IB HL OPTION OBJECTIVE
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G.9.1 Describe, using equations, the reactions of
acid anhydrides with nucleophiles to form
carboxylic aicds, esters, amides and substituted
amides.
Include the nucleophiles: water, alcohols,
ammonia and amines.
G.9.1 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACID
ANHYDRIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC AICDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acid Anhydrides
H3C
•
O
O
C
C
O
CH3
Ethanoic anhydride
Acid Anhydrides are often used in organic
synthesis reactions because they are more
reactive than a carboxylic acid. The –OCOR
group is a better leaving group than an –OH
group.
G.9.1 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACID
ANHYDRIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC AICDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acid Anhydride with Water
Can react with water to go back to two ethanoic
acids.
H3C
O
O
C
C
O
CH3
O
+ H 2O
2
H3C
C
OH
G.9.1 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACID
ANHYDRIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC AICDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acid Anhydride with Alcohol
Can react with ethanol to form an ester.
H3C
O
O
C
C
O
CH3
O
+
H3C
CH2 OH
C
H3C
O
CH2 CH3
+ CH3COOH
What common drug can be made in this reaction
from salicylic acid?
G.9.1 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACID
ANHYDRIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC AICDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acid Anhydride with Ammonia
Can react with ammonia to form an amide.
H3C
O
O
C
C
O
CH3
O
+ NH3
+ CH3COOH
C
H3C
NH2
G.9.1 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACID
ANHYDRIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC AICDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acid Anhydride with Amines
Can react with amines to form secondary amides.
H3C
O
O
C
C
O
CH3
NH2
NH
+
CH3
C
HO
O
HO
+ CH3COOH
What is the common name of the structure on the right, and what is it
used for?
IB HL OPTION OBJECTIVE
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G.9.2 Describe, using equations, the reactions of
acyl chlorides with nucleophiles to form
carboxylic acids, esters, amides and substituted
amides.
Include the nucleophiles: water, alcohols,
ammonia and amines.
G.9.2 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACYL
CHLORIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC ACIDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acyl Chlorides
O
H3C
C
Cl
Ethanoyl chloride
•
The chloride makes an even better leaving group
than acid anhydride. It is more reactive.
G.9.2 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACYL
CHLORIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC ACIDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acyl Chloride with water
O
H3C
C
Cl
O
+ H2O →
H3C
+ HCl
C
OH
Notice how instead of the other product being ethanoic
acid, it is now HCl. This will be the same throughout.
G.9.2 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACYL
CHLORIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC ACIDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acyl Chloride with alcohol
O
H3C
C
Cl
O
+
H3C
CH2 OH
C
H3C
O
CH2 CH3
Notice a trend here? How does this compare to the
products from the acid anhydride?
G.9.2 DESCRIBE, USING EQUATIONS, THE REACTIONS OF ACYL
CHLORIDES WITH NUCLEOPHILES TO FORM CARBOXYLIC ACIDS,
ESTERS, AMIDES AND SUBSTITUTED AMIDES.
Acyl Chloride with alcohol
O
H3C
C
Cl
Can you predict the products for the reactions with
ammonia and ethanamine?
IB HL OPTION OBJECTIVE
G.9.3 Explain the reaction of acyl chlorides with
nucleophiles in terms of addition-elimination
mechanism.
 Check out the mechanism in your study guide.
Draw the mechanism with curly arrows on a
sheet of paper!
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IB HL OPTION OBJECTIVE
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G.10.1 Describe, using equations, the nitration,
chlorination, alkylation and acylation of benzene.
Include the use of
for the benzene ring as
well as formulas such as C6H5NO2.
 The introduction of more than one group into the
benzene ring will not be assessed here.
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G.10.1 DESCRIBE, USING EQUATIONS, THE NITRATION,
CHLORINATION, ALKYLATION AND ACYLATION OF BENZENE.
Benzene has a high electron density due to the
presence of delocalized pi electrons.
 This makes benzene susceptible to electrophilic
attack.
 However, benzene does not readily undergo
addition reactions, since addition would disrupt
the stability of the delocalized pi bonds.
 Therefore, reactions with benzene undergo
electrophilic substitution reactions.
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G.10.1 DESCRIBE, USING EQUATIONS, THE NITRATION,
CHLORINATION, ALKYLATION AND ACYLATION OF BENZENE.
Benzene reacts with nitric acid and concentrated
sulfuric acid at 50̊C.
 This reaction creates nitrobenzene. Write the
equation for this reaction along with byproducts.
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IB HL OPTION OBJECTIVE
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G.10.2 Describe and explain the mechanisms for
the nitration, chlorination, alkylation and
acylation of benzene.
Include the formation of NO2+ from the reaction
between concentrated nitric and sulfuric acids,
and the formation of Cl+, R+, and RCO+ from
reactions involving aluminum chloride as a
halogen carrier catalyst.
G.10.2 DESCRIBE AND EXPLAIN THE MECHANISMS FOR THE
NITRATION, CHLORINATION, ALKYLATION AND ACYLATION OF
BENZENE.
Nitrobenzene
 In the reaction of nitric acid with benzene to
produce nitrobenzene, sulphuric acid acts as a
catalyst.
 Sulphuric acid protonates the nitric acid which
produces water.
 The nitronium ion (NO2+) then attacks the
benzene. In order to regain the stability of the
delocalized electrons, the hydrogen leaves which
regenerates the catalyst.
G.10.1 DESCRIBE, USING EQUATIONS, THE NITRATION, CHLORINATION,
ALKYLATION AND ACYLATION OF BENZENE.
G.10.2 DESCRIBE AND EXPLAIN THE MECHANISMS FOR THE NITRATION,
CHLORINATION, ALKYLATION AND ACYLATION OF BENZENE.
•
•
•
•
Chlorination
In order for benzene to undergo addition with
chlorine, a halogen carrier, aluminum chloride
(AlCl3), is needed as a catalyst.
Aluminum chloride can act as a Lewis acid
(electron acceptor) since there are only six
electrons around the aluminum atom.
Aluminum chloride will attract a Cl- from the
chlorine (Cl2), and you now have a Cl+ ion (strong
electrophile).
After Cl+ attacks, the hydrogen is released, which
creates HCl, regenerating the catalyst.
G.10.1 DESCRIBE, USING EQUATIONS, THE NITRATION, CHLORINATION,
ALKYLATION AND ACYLATION OF BENZENE.
G.10.2 DESCRIBE AND EXPLAIN THE MECHANISMS FOR THE NITRATION,
CHLORINATION, ALKYLATION AND ACYLATION OF BENZENE.
Friedel-Crafts Reactions
 Friedel-Crafts reactions are using halogen
carriers (AlCl3), reacting them with halogenated
organic compounds (C2H5Cl), to create
electrophilic chains (R+ and RCO+). These alkyl
and acyl groups are then substituted into the
benzene ring.
 Use equations and show the mechanism for when
benzene reacts with chloroethane. Show the
products.
G.10.1 DESCRIBE, USING EQUATIONS, THE NITRATION, CHLORINATION,
ALKYLATION AND ACYLATION OF BENZENE.
G.10.2 DESCRIBE AND EXPLAIN THE MECHANISMS FOR THE NITRATION,
CHLORINATION, ALKYLATION AND ACYLATION OF BENZENE.
Acylation
 Remember ethanoyl chloride?
O
H3C
C
Cl
Show the reaction of ethanoyl chloride and benzene
using aluminum chloride as a catalyst to form
phenylethanone.
IB HL OPTION OBJECTIVE
G.10.3 Describe, using equations, the nitration,
chlorination, alkylation and acylation of
methylbenzene.
 G.10.4 Describe and explain the directing effects
and relative rates of reaction of different
substituents on a benzene ring.
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G.10.4 DESCRIBE AND EXPLAIN THE DIRECTING EFFECTS
AND RELATIVE RATES OF REACTION OF DIFFERENT
SUBSTITUENTS ON A BENZENE RING.
The methyl group in methylbenzene has a
positive inductive effect (i.e. it pushes electrons
towards the ring rather than pulling electrons
from it).
 Methylbenzene is thus more reactive to
electrophiles, and CH3 is known as an
activating group.
 NO2, as learned earlier, pulls electrons towards
it, and decreases the reactivity of benzene. Thus,
NO2 is an example of a deactivating group.
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G.10.3 DESCRIBE, USING EQUATIONS, THE NITRATION, CHLORINATION,
ALKYLATION AND ACYLATION OF METHYLBENZENE.
The methyl group on methylbenzene is like a
director….
 It directs the electrophiles to the 2 or 4 position
on the benzene ring.
 Therefore, if chlorine reacts with methylbenzene,
only 2-chloromethylbenzene and 4chloromethylbenzene are formed. This is due to
the positive inductive effect of the CH3 group
making a 2 or 4 intermediate more energetically
stable.
 This will be true for all substituents to
methylbenzene (NO2, Cl, R, and CO-R)
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G.10.4 DESCRIBE AND EXPLAIN THE DIRECTING EFFECTS AND
RELATIVE RATES OF REACTION OF DIFFERENT SUBSTITUENTS ON
A BENZENE RING.
-OH group
 Even though oxygen is electronegative here, it
actually partially donates a non-bonded pair of
electrons to the benzene ring, making it more
reactive.
 At room temperature, phenol will rapidly react
with aqueous chlorine to produce 2,4,6trichlorophenol (notice the locations of the
chlorines).
G.10.4 DESCRIBE AND EXPLAIN THE DIRECTING EFFECTS AND
RELATIVE RATES OF REACTION OF DIFFERENT SUBSTITUENTS ON
A BENZENE RING.
NO2 group
 NO2, as mentioned earlier, is electron
withdrawing, so it is deactivating (it does not
have a non-bonding pair on the nitrogen to
partially donate).
 Therefore, it will not be directed to the 2,4 spots,
but instead the 3 spot.
 For those of you who were here, we performed a
lab where we added nitrobenzene with
concentrated nitric acid and refluxed for a while
with concentrated sulfuric acid to produce 1,3dinitrobenzene.