Aromaticity Chemistry Assignment Help




homework assignment help is most useful online help portal for the students that providing all Online Aromaticity Chemistry assignment help Services.Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. It can also be considered a manifestation of cyclic delocalization and of resonance.

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Aromatic Hydrocarbon:

  Natural sources like resins, balsams, aromatic oils etc., contain aliphatic compounds and also a group of compounds with pleasant odorous. These odorous compounds were arbitrarily classified as aromatic. Most of the simple aromatic hydrocarbon compounds were found to contain six carbon atoms. Further when aromatic compounds were subjected to various methods of treatment, they often produced benzene or a derivative of benzene. Hence these aromatic compounds are called benzenoid compounds.

Aromatic Hydrocarbon Compounds:

Benzene C6H6 was first inaccessible by Faraday as of cylinders of condensed enlightening gas obtained from the pyrolysis of whale oil. In 1845 benzene was establish in coal-tar by hofmann with this is immobile a source of benzene and derivative. Benzene was first synthesised through berthelot by passing acetylene through a red-hot tube.

3C2 H2  `->` C6H6 + other products.

It may be prepared in the laboratory by decarboxylation of aromatic acids.

The organic chemistry the word aromatic be use to explain aromatic substances such like benzaldehyde, toluene etc. Aromatic represent to benzene and structural homologues.

Many hydrocarbon compound inaccessible from natural source are aromatic to benzene toluene and benzaldehyde, complex compounds such as the female steroidal harmone estrone and the well known analgesis, morphine have aromatic rings. Many synthetic drugs used medicinally are also aromatic in part.

Benzene is the first in the aromatic series of compounds. The whole series of compounds which contain one or more benzene rings in their molecules are called aromatic hydrocarbon compoundas. Certain heterocyclic compounds like pyridine which do not have benzene rings also come under this classification.

  • Benzene
  • Toluene
  • Benzaldehyde
  • Naphthalene
  • Anthracene
  • Pyridine

Physical Properties:

          Liquids or solids with characteristic. They are insoluble in water but are miscible in all proportions with organic solvents such as ethanol, ether etc. they are inflammable and burn with sooty flame. Toxic also carcinogenic in character. The boiling points increase with increase in molecular weight, but their melting points do not exhibit regular gradation melting point to depend on molecular symmetry then on molecular weight.

Commercial Preparation of Benzene Form Coal Tar - Aromatic Hydrocarbon:

The two main sources of aromatic hydrocarbons are coal and petroleum. Coal is a complex substance made of primarily large arrays of highly unsaturated benzene like rings  linked together. When coal is heated 10 1000 C in the absence of air, thermal break down of coal molecules occur and a mixture of volatile products called coal tar distills off.

The coal tar forms the source of many organic compounds. Further distillation of coal tar yields benzene, toluene, xylene, naphthalene and a host of other aromatic compounds.

  

Naming aromatic hydrocarbons :-

Friedrich August Kekule von Stradonitz found the first aromatic hydrocarbon in 19th century. The first aromatic compound he found was Benzene in which he states that benzene has six carbon atoms with four electrons on each carbon atom. He also explains the presence of resonance in Benzene. He further signifies that there is a series of alternate single and double bonds in Benzene.        

Naming about Aromatic Hydrocarbons

In short forms aromatic hydrocarbons are written as AH. The aromatic hydrocarbons are also known by the names Arene and Aryl hydrocarbons. The aromatic hydrocarbons are said to have cyclic structures having series of alternate double and single bonds. The aromatic hydrocarbons possess more stability than the simple hydrocarbons. The term aromatic is used because it has been seen that all aromatic hydrocarbons have very sweet smell. The simplest aromatic compound, which is also the first aromatic compound, is Benzene, which has six carbon atoms arranged in a ring with alternate double and single bonds. Aromatic hydrocarbons are classified into two categories:

  1. Monocyclic
  2. Polycyclic

How to Name Aromatic Hydrocarbons

All the aromatic hydrocarbons are entirely depend on Benzene. There must be at least one Benzene ring present in the Aromatic compounds. The Aromatic compounds are named as follows:

Any other group attached to Benzene ring is said to be the side chain like CH3, CH2Cl, CH2OH, CH2NH2, NO2, OH, NH2, etc.

 

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Different Names of Aromatic Hydrocarbons

As per their classification, aromatic compounds, which are Monocyclic, are named as:

  • Methyl group (CH3)  on Benzene is named as Toluene
  • NO2 group on Benzene is named as Nitrobenzene
  • OH group on Benzene is named as Phenol

Aromatic compounds, which are polycyclic, are named as:

  • The Aromatic compounds, which have two benzene rings together, are named as Naphthalene.
  • The Aromatic compounds, which have three benzene rings together, are named as Anthracene.

The hydrogen atoms are removed in also other Aromatic Hydrocarbons. Such types of aromatic hydrocarbons are named as Aryl hydrocarbons. By help of the following table the naming of these hydrocarbons is done:

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                           Image showing the naming of Aryl compounds

The aromatic hydrocarbons are based on the benzene acting as a base. Aromatic hydrocarbons are different types of Benzene compounds; the only difference is that they have different groups attached to them.


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