AROMATIC COMPOUNDS
l alifatis compounds: methane derivatives
l aromatic compounds: benzene derivatives (symbol Ar = aryl)
l The beginning of the 19th century found the organic compounds that have a smell (scent) that the characteristics that come from plants (benzoin resin, cumarin, cinnamic acid, etc.)
Benzene = C6H6
l The most simple aromatic compounds
l Derived from coal and petroleum
l Physical properties: fluid, td. 80oC, colorless, insoluble in water, soluble in most organic solvents, flammable with a sooty flame and colored (because of the high C content)
Use of benzene:
l In the past as a motor fuel
l The solvent for many substances
l Synthesis: styrene, phenol, nylon, aniline, isopropyl benzene, detergents, insecticides, maleic acid anhydride, etc
l aromatic compounds: benzene derivatives (symbol Ar = aryl)
l The beginning of the 19th century found the organic compounds that have a smell (scent) that the characteristics that come from plants (benzoin resin, cumarin, cinnamic acid, etc.)
Benzene = C6H6
l The most simple aromatic compounds
l Derived from coal and petroleum
l Physical properties: fluid, td. 80oC, colorless, insoluble in water, soluble in most organic solvents, flammable with a sooty flame and colored (because of the high C content)
Use of benzene:
l In the past as a motor fuel
l The solvent for many substances
l Synthesis: styrene, phenol, nylon, aniline, isopropyl benzene, detergents, insecticides, maleic acid anhydride, etc
One fact shows that although benzene compounds have double bonds but it can not react with KMnO4 (oxidized) and undergo electrophilic addition reactions such as alkene compounds.
This is due to benzene compounds having double bonds can resonate so intermittent alternating double bond character is lost.
Benzene:
Evidence that the double bond character is missing from the bond length of each bond in benzene. If there is still a long double bond C = C bond should be a single bond 1:34 and 1:54 Å Å. In fact CC bond length of benzene is the same, namely 1:40 Å
Other evidence is to measure the thermodynamic heat of hydrogenation. Supposed to heat the hydrogenation of cyclohexene was 28.6 kcal per mole. For the three double bond of 1,3,5 sikloheksatriena should heat of hydrogenation is 85.8 kcal per mole. But the fact that benzene has a lower heat of hydrogenation of 36 kcal / mole. And the excess energy is called resonance energy of benzene, which is characteristic of aromatic compounds
Depictions of the molecular orbitals can better explain the nature kearomatisan of benzene. Benzene has a planar hexagon shape which all the atoms form sp2 Cnya with CC bond lengths are all the same. As shown in the figure below, six p orbitals for each carbon overlapping each other to form six molecular orbitals are divided into three bonding orbitals and the three orbital antiikatan. In the bond orbital lowest energy valence electrons which 12 have overlapping benzene rings perfect that thermodynamically and chemically more stable.
TERMS OF AROMATIC COMPOUNDS
Not all compounds that have double bonds that berselangseling with single bonds (a conjugated double bond) can be classified as an aromatic compound
Which includes aromatic compounds the conditions are:
1. Sp2 atoms in a ring oriented in the planar molecular shape (near-planar), the p orbital parallel to each other in the same direction
2. Meet the Huckel rule is л = 4n +2 for n price aromatic compound must be an integer
This is due to benzene compounds having double bonds can resonate so intermittent alternating double bond character is lost.
Benzene:
Evidence that the double bond character is missing from the bond length of each bond in benzene. If there is still a long double bond C = C bond should be a single bond 1:34 and 1:54 Å Å. In fact CC bond length of benzene is the same, namely 1:40 Å
Other evidence is to measure the thermodynamic heat of hydrogenation. Supposed to heat the hydrogenation of cyclohexene was 28.6 kcal per mole. For the three double bond of 1,3,5 sikloheksatriena should heat of hydrogenation is 85.8 kcal per mole. But the fact that benzene has a lower heat of hydrogenation of 36 kcal / mole. And the excess energy is called resonance energy of benzene, which is characteristic of aromatic compounds
Depictions of the molecular orbitals can better explain the nature kearomatisan of benzene. Benzene has a planar hexagon shape which all the atoms form sp2 Cnya with CC bond lengths are all the same. As shown in the figure below, six p orbitals for each carbon overlapping each other to form six molecular orbitals are divided into three bonding orbitals and the three orbital antiikatan. In the bond orbital lowest energy valence electrons which 12 have overlapping benzene rings perfect that thermodynamically and chemically more stable.
TERMS OF AROMATIC COMPOUNDS
Not all compounds that have double bonds that berselangseling with single bonds (a conjugated double bond) can be classified as an aromatic compound
Which includes aromatic compounds the conditions are:
1. Sp2 atoms in a ring oriented in the planar molecular shape (near-planar), the p orbital parallel to each other in the same direction
2. Meet the Huckel rule is л = 4n +2 for n price aromatic compound must be an integer
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