Organic Chemistry: Aromaticity
15. Benzene and Aromaticity
• C-Phen DM Drops (Chlorpheniramine/Dextromethorp/Phenylephrine)
• This combination medication is used to treat symptoms caused by the common cold, flu, allergies, hay fever, or other breathing illnesses (e.g., sinusitis,bronchitis). • One of the active ingredients is Phenylephrine –a decongestant that helps relieve stuffy nose symptoms.
H
HO
OH
H
N
CH3
. HCl
What is the configuration at this chirality center? R or S ? www.primaryrx.com/pdf/C-PHEN%20DM%20DROPS.pdf 1
Chapter 15: Benzene and Aromaticity
Introduction:
• All organic compounds can be derived into two broad classes
1.
Aliphatic compounds
Nonaromatic hydrocarbons such as alkanes, alkenes or alkynes
2.
Aromatic compounds
A series of cyclic unsaturated compounds with unusually high stability
• The properties and reactions of aromatic compounds are exemplified / demonstrated by the properties and reactions of benzene (the “parent” aromatic molecule)
• Benzene
Structure:
MF: C6H6
DBE =
• Properties and Reactions of Benzene
1. Benzene, being unsaturated, would be expected to react like typical olefinic compounds. But this is not the case, for example:
2
Br
Br2
Br2
CCl4
CCl4
Br
No reaction
BUT
OH
KMnO4
-
KMnO4
-
OH
No reaction
OH
OH
Conclusion: Benzene is stable to both Br2 / CCl4 and KMnO4 / -OH. Therefore, there is something unusual about the double bonds in benzene, the unsaturation is atypical / unique
2. Benzene undergoes substitution rather than addition reaction, i.e.,
Br
Br
Br2
+
HBr
FeBr3
Br
Addition product not observed
This observation is contrary to that of unsaturated aliphatic compounds e.g. alkenes.
Benzene is far more stable than typical alkenes
3
3. Benzene gives only ONE monosubstituted product
Br
H
Br2
ect
=
FeBr3
Br
Conclusion: All the hydrogens in benzene are equivalent and hence the molecules is highly
• C-Phen DM Drops (Chlorpheniramine/Dextromethorp/Phenylephrine)
• This combination medication is used to treat symptoms caused by the common cold, flu, allergies, hay fever, or other breathing illnesses (e.g., sinusitis,bronchitis). • One of the active ingredients is Phenylephrine –a decongestant that helps relieve stuffy nose symptoms.
H
HO
OH
H
N
CH3
. HCl
What is the configuration at this chirality center? R or S ? www.primaryrx.com/pdf/C-PHEN%20DM%20DROPS.pdf 1
Chapter 15: Benzene and Aromaticity
Introduction:
• All organic compounds can be derived into two broad classes
1.
Aliphatic compounds
Nonaromatic hydrocarbons such as alkanes, alkenes or alkynes
2.
Aromatic compounds
A series of cyclic unsaturated compounds with unusually high stability
• The properties and reactions of aromatic compounds are exemplified / demonstrated by the properties and reactions of benzene (the “parent” aromatic molecule)
• Benzene
Structure:
MF: C6H6
DBE =
• Properties and Reactions of Benzene
1. Benzene, being unsaturated, would be expected to react like typical olefinic compounds. But this is not the case, for example:
2
Br
Br2
Br2
CCl4
CCl4
Br
No reaction
BUT
OH
KMnO4
-
KMnO4
-
OH
No reaction
OH
OH
Conclusion: Benzene is stable to both Br2 / CCl4 and KMnO4 / -OH. Therefore, there is something unusual about the double bonds in benzene, the unsaturation is atypical / unique
2. Benzene undergoes substitution rather than addition reaction, i.e.,
Br
Br
Br2
+
HBr
FeBr3
Br
Addition product not observed
This observation is contrary to that of unsaturated aliphatic compounds e.g. alkenes.
Benzene is far more stable than typical alkenes
3
3. Benzene gives only ONE monosubstituted product
Br
H
Br2
ect
=
FeBr3
Br
Conclusion: All the hydrogens in benzene are equivalent and hence the molecules is highly